Greenhouse tomato growers produce vineripe tomatoes at a time of year whenhomegrown tomatoes are not available.Many disease and insect pests can attackgreenhouse-grown tomatoes and hurtboth production and quality. Greenhousetomato producers must be able to accu-rately scout for and identify these pestsand know how to effectively and econom-ically control them.

Growers who successfully combatgreenhouse tomato pests rely on integrat-ed pest management (IPM). IPM simplymeans that growers use a combination ofbiological, cultural, and chemical methodsto suppress pest populations, rather thanrelying only on one method, such asrepeated insecticide use. This integratedapproach uses preventive measures toavoid likely insects and diseases, cropmonitoring to allow early detection, bio-logical control when possible, and pesti-cides when needed. A sound IPM pro-gram reduces pesticide use, allows moretimely application of needed pesticidetreatments, and improves pest control.

Insect ManagementMany of the same insect pests that attackfield-grown tomatoes also attack green-house tomatoes. But because of theenclosed, controlled environment of thegreenhouse, insect management is differ-ent from what is used in the field. Themost important components of insectmanagement in greenhouse tomatoes arediscussed below.

ExclusionExclusion, keeping insects from enteringthe greenhouse, is a key part of green-house insect management. Many common

pests that attack greenhouse tomatoes aresmall flying or windborne creatures thatcan easily be sucked into the greenhousethrough ventilation fans and cooling padsor can easily enter through other open-ings. By building the greenhouse so thatit is “bug tight,” growers can avoid manyserious insect infestations. Althoughbuilding an insect-proof greenhouserequires additional planning and expense,it is well worth it.

One of the first steps in building aninsect-proof greenhouse is to install prop-er screening over air intake vents or cool-ing mats. Because many greenhouse insectpests are so small, it takes very finescreening to exclude them. Thrips are thesmallest insect pests that need to bescreened out, and a screen mesh of 81x81is required. Obviously, screening thatkeeps out thrips also keeps out largerpests, such as aphids and whiteflies.

One very important point to keep inmind when installing screening overintake vents or cooling mats is that suchfine mesh screens greatly reduce airflow.So if you install screening, you may needto build special screen-covered enclosuresover the vents that support enough screensurface area to provide the necessary airflow. Greenhouse manufacturers and sup-pliers sell screening of various openingsizes and can provide information andguidance on proper installation to achievethe necessary airflow.

In addition to properly screening airintake points, it is also important to besure that any other possible entries aresealed. Even in properly screened andsealed greenhouses, insect pests can enteror be sucked into the greenhouse throughthe door as workers come and go. Adding

Greenhouse TomatoesPest Management in Mississippi

an air-lock or enclosed porch over the door is an inex-pensive way to prevent this kind of insect entry. Ofcourse, once you have gone to the trouble and expenseof screening and sealing a greenhouse, it is importantto properly maintain the exclusion devices. Repairholes or tears immediately, and clean screening tomaintain airflow.

SanitationSanitation is another major part of greenhouse pest man-agement. Many tomato pests also occur on other cropsor broadleaf weeds. For this reason, it is important toavoid growing other crops next to the greenhouse and toprevent heavy growths of broadleaf weeds around theoutside edges of the greenhouse. Not letting weeds andvolunteer plants grow inside the greenhouse, duringeither cropping or noncropping periods, is even moreimportant, because such plants can serve as hosts for anumber of pests and can let pests survive inside thegreenhouse during noncrop periods.

One of the most important points in sanitation isto begin with insect-free transplants and avoid bring-ing other plants into the greenhouse once you plantthe crop. Serious infestations of insects or diseases canbe introduced on new plants, either vegetables orornamentals, that are brought into the greenhouse orexchanged with other growers. It is best to avoid thisentirely. If new plants are introduced, quarantine themin another location and closely observe them for sever-al days to be sure they are pest free.

Finally, keep the greenhouse clean and free ofdebris. Promptly remove pruned leaves as well as culland over-ripe fruit.

ScoutingScouting and early detection are critical to successfulinsect control. Purposefully inspect plants one to twotimes per week to check for developing insect prob-lems. Do this by walking through the greenhouse,making random stops, and visually examining bothupper and lower leaf surfaces as well as buds, blooms,and fruit for insect pests. Give extra attention to plantsor areas that show unusual symptoms or appearance.Many insect infestations begin in isolated spots withinthe greenhouse but quickly spread if not controlled.Because many insects and mites are so small, a 10 to20X hand lens is an important tool to use when scout-ing. Also be alert for insect pests when performingroutine maintenance procedures, such as pruning,training, or harvesting.

There are a number of pest management tools youcan use in addition to visual scouting. Yellow stickycards from greenhouse supply companies can helpdetect whiteflies and many other greenhouse pestsearly. Pheromone traps available for tomato pinwormcan allow critical early detection if you use themaccording to directions and replace the lure as required.

Cultural PracticesMany cultural practices can help reduce insect popula-tions. Maintaining good weed control and not bring-ing other plants into the greenhouse were discussed inthe “Sanitation” section. Pruning lower leaves afterharvesting lower fruit clusters is another helpful meas-ure in horticultural and disease management. This canalso aid in insect control by removing large numbersof developing leafminers and whiteflies. But growerspracticing biological control need to remember thatexcessive leaf removal can interfere with biologicalcontrol efforts by removing parasitized pests beforethe parasites emerge. Managing irrigation to avoidleaks and excessive moisture aids in control of fungusgnats.

Biological Control Biological control can be a viable alternative to usinginsecticides in greenhouse tomato production andworks especially well with using bumble bees for pol-lination. Successful biological control requires careful,frequent scouting, accurate pest identification, knowl-edge of the pest biology, knowledge and understand-ing of the biology of the biocontrol agents used, andcareful selection and timely release of biocontrolagents. One key to successful biocontrol is to under-stand that it is not meant to eliminate all insect pests.Low levels of pests must be present to provide foodfor the biological control agents. It is important tobegin releases of biological control agents when pestpopulations are low to keep them from reaching dam-aging levels.

Several suppliers specialize in developing andproducing predatory and parasitic insects and mites,along with other biological control agents, for use ingreenhouses. If you are interested in using thisapproach, contact suppliers to learn details aboutwhich species are available, recommended releaserates, specific environmental conditions under whichthe agent performs best, frequency of release, cost, andother information. Keep in mind that biological controlagents are living organisms, and the quality of theagents can differ between sources. Success of biocon-trol often depends on careful management of environ-mental conditions, especially temperature and humidi-ty. Certain species of predators or parasites performbest under certain conditions, and in some cases differ-ent strains of the same species are available for differ-ent conditions.

One of the major factors affecting success of bio-logical control efforts is insecticide use. For example,you cannot conduct a successful biological control pro-gram against whiteflies if broad-spectrum, long-resid-ual insecticides are being used regularly in the green-house to control other pests. The biological controleffort must target all major pests likely to occur in thegreenhouse. When insecticide sprays are required,

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carefully select products compatible with any biologi-cal control agents being used. Fortunately, a number ofbiopesticide and insect growth regulator (IGR) typeproducts meet this requirement.

InsecticidesInsecticides are the last resort in any IPM system.However, insecticide use is often needed to keep pestpopulations from reaching damaging levels. Whenusing any pesticide in greenhouses, read and follow alllabel instructions. Be sure to wear appropriate protec-tive equipment because pesticide exposure can begreater in enclosed areas. Using properly fitting respi-rators is especially important when making pesticideapplications in greenhouses. Also take care to useappropriate rates. Applying pesticides at excessiverates can result in plant injury and other problems.

Most insect pests of geenhouse tomatoes occur onthe undersides of leaves, and you will not get goodcontrol unles you spray the bottoms of the leaves.Because pest populations are often hightest on thelower, older leaves, it is especially important to be sureto treat the undersides of lower leaves. Using adequtespray volume and taking the time necessary to treatthe leaf undersides thoroughly, expecially lowerleaves, is critical to achieving good control with insec-ticide sprays. Poor control is often the result of poor,hastily-made applications.

Major Insect Pests

AphidsGreen peach aphid Myzus persicaePotato aphid Macrosiphum euphorbiaeSeveral other species

Aphids (plant lice) are small, soft-bodied insectsthat differ in color from light green or yellow to pink,red, or black. There are several different species, andall of them suck plant juices, causing leaves to curl andturn yellow. Some species inject toxic saliva or disease-causing organisms during feeding. Heavy aphid infes-tations may cause a failure of bloom set in some veg-etable crops. Aphids excrete large amounts of stickyundigested plant sap, known as honeydew, which cansupport the growth of sooty mold fungus. Althoughsooty mold fungus does not attack the plant directly,heavy amounts of honeydew and sooty mold can dis-color fruit and interfere with photosynthesis.

BiologyMost aphid species reproduce without mating andgive birth to live aphid nymphs rather than layingeggs. Under the best conditions, the nymphs, whichare usually all females, can reach maturity and beginbearing young of their own within 7 days. Because ofthis high reproductive rate, heavy infestations candevelop quickly. Mature females may be winged orwingless depending on environmental conditions.

Infestations easily spread through the wind-assistedflight of winged females. Although aphids usuallyhave a fairly narrow host range, many species occuron a number of vegetable plants as well as certainweeds. Outdoors, aphids are preyed on and para-sitized by many beneficial insects, and this naturallyoccurring biological control normally keeps aphidpopulations in check. Outbreaks occur when aphidpopulations get ahead of biological control or whenbiological control is disrupted by insecticide treat-ments targeted toward other pests.

ManagementExclusion and sanitation are important in avoidingaphid infestations. Proper screening of ventilation fansand keeping greenhouses “bug tight” will prevententry of windborne females. Do not allow weeds andother plants to grow in the greenhouse during non-crop periods, and maintain control of broadleaf weedsaround the outside edges of the greenhouse. Also, donot allow other plants to be brought into the green-house when a crop is in production. Aphid infestationsoften begin in isolated areas within the greenhouse,and prompt spot treatments can eliminate these infes-tations before they spread. Several biological controlagents are available for use against aphids in green-houses, including generalist predators, such aslacewings and lady beetles, and several species of par-asitic wasps.

Insecticides for Aphid ControlAzadirachtin, Beauvaria bassiana, malathion, paraffinicoil, potassium salts of fatty acids, pyrethrins.

Paraffinic oil, potassium salts of fatty acids andpyrethrins provide contact control but have very shortresidual activity. The biopesticide Beauvaria bassiana isa fungal disease that infects aphids.

WhitefliesSilverleaf whitefly Bemesia argentifoliiGreenhouse whitefly Trialeurodes vaporariorum

Whiteflies are the most common and most prob-lematic insect pests of greenhouse tomatoes. Despitetheir name, whiteflies are not true flies; they are close-ly related to aphids. Adults are about 1/16 inch longand have four wings covered with a white, powderymaterial. They rest with their wings folded tent-likeover their backs and are weak fliers. Immature white-flies are very different from adults. Except for thenewly hatched crawlers, immatures are immobilescale-like insects. They look like tiny, oval scalesattached to the undersides of leaves. Whiteflies causedamage by sucking sap from plants and producinghoneydew, which supports the growth of sooty mold.These insects can build up to very high levels in pro-tected greenhouse environments and are capable ofcausing severe crop loss.

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There are several different species of whiteflies,but the two most common species in greenhousetomatoes are greenhouse whitefly and silverleaf white-fly. Of these, silverleaf whitefly is the bigger threat andis more difficult to control. Silverleaf whiteflies cantransmit several significant tomato viral diseases, andthey also cause a problem known as irregular ripen-ing. This is thought to be physiologically induced,meaning that it is not caused by disease but is an indi-rect result of the whitefly infestation.

It is important to know which species of whiteflyyou are dealing with before implementing treatments.Proper species identification is especially importantwhen using biological control, because many biologi-cal control agents only work on a certain species. Theparasitic wasp Encarsia formosa is especially effectiveagainst greenhouse whitefly, but other parasites aremore effective against silverleaf whiteflies.

BiologyFemale whiteflies lay about 150 eggs, usually attachedto the undersides of leaves. In greenhouses, eggs hatchin 4 to 7 days into tiny, white, oval crawlers. Thesemove a short distance, insert their mouthparts into theplant tissue, produce a protective scale-like covering,and do not move for the rest of their nymphal devel-opment. Nymphs go through three instars and a pupastage before reaching adulthood. The winged adultsemerge through a slit in the pupal covering. Fulldevelopment usually takes 25 to 30 days in greenhous-es. Adults may live up to 30 days.

ManagementYellow sticky cards placed in the upper plant canopyare useful for monitoring whitefly populations .Exclusion and sanitation are the keys to whitefly man-agement. You can also buy and release certain preda-tors and parasites into the greenhouse system to man-age whiteflies. But to be effective, biological controlmust be well planned and begun when whitefly popu-lations are low. It is important to know which speciesof whitefly you are targeting with biocontrol efforts.For example, Encarsia formosa can provide good controlof greenhouse whiteflies, but silverleaf whiteflies aremore effectively controlled by Eretmocerus wasps.There are also some predatory insects, such as the tinylady beetle Delphastus pusillus, that attack whiteflies.Biopesticides, such as Beauveria bassiana fungus, arealso useful in controlling whiteflies.

Although you need low levels of whiteflies whenimplementing biological control, good exclusion prac-tices are still important. If other pests are present, youmight have to make insecticide applications thatwould disrupt the biological control program.Properly screened greenhouses also keep expensivebiological agents from escaping after their release.

Insecticides for Whitefly Control Azadirachtin, Beauvaria bassiana, buprofezin, paraffinic oil,potassium salts of fatty acids, pyrethrins, pyriproxyfen.

Effective control of whiteflies depends on con-trolling the immature stages. Azadirachtin is a botani-cal insect growth regulator useful against whiteflies.It controls the immatures and has a short preharvestinterval (PHI). Buprofezin (Talus) and pyriproxyfen(Distance) are insect growth regulators that are veryuseful against whiteflies. Paraffinic oil, and potassiumsalts of fatty acids provide contact control of adultsand crawlers. Pyrethrins will provide short-term con-trol of adults, but these products will not controlimmature whiteflies.

Whiteflies are difficult to control with insecticidesbecause the eggs and nonfeeding pupae are not con-trolled by either contact or systemic treatments, andthe actively feeding nymphs are hard to control withcontact insecticides. To control whiteflies with insecti-cides, it is important to scout regularly and begin con-trol efforts when whiteflies are first detected. There areseveral insecticides that kill exposed adult whiteflies,but effective control of whiteflies depends on control-ling the immature stages. Fortunately, greenhousegrowers now have access to several systemic or insectgrowth regulator products that are effective againstwhiteflies. The growth regulators buprofezin (Talus)and pyriproxyfen (Distance) are especially usefulwhitefly control tools.

When applying foliar sprays for whiteflies, it isbest to spray when the temperature is 70 to 80 °F.Because whiteflies can quickly develop resistance toinsecticides they are exposed to repeatedly, pay closeattention to information on labels about resistancemanagement guidelines and alternate insecticide use.

Tomato Psyllids Paratrioza cockerelliTomato psyllids are more common in western

regions but have not yet been found in greenhouses inMississippi. Still, Mississippi growers need to beaware of these pests. Psyllids are relatives of aphidsand whiteflies. Adults are only about 1/10 inch longand look like miniature cicadas. They have clear wingsthat are folded roof-like over the body when the insectis resting. The small nymphs are tan, yellow, or greenand roughly oval-shaped and flat. Mature nymphs area little less than 1/16 inch long. They somewhatresemble immature whiteflies. Psyllid nymphs havedistinct red eyes, but immature silverleaf whitefliesalso have red eyes at certain points in their develop-ment. Nymphs and adults produce large amounts ofwhite, waxy material that builds up in areas where theinsects feed. This material is often one of the first indi-cators of psyllid infestations.

Tomato psyllids also occur on potatoes and otherplants and weeds in the nightshade family, known as

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solanaceous plants. The nymphs inject a toxin into theplant that results in a condition known as “psyllid yel-lows.” As the name implies, affected plants have a yel-lowing midrib and leaf margins and upward-curlingleaves. Severely affected plants may be stunted andhave a faded purple color. Infested plants can sufferfrom greatly reduced growth and fruit production. Ittakes only a few nymphs per plant to cause these seri-ous symptoms.

BiologyFemale psyllids can lay several hundred eggs whichthey place on stalks on the undersides of leaves. Eggshatch in about 4 days, and the resulting nymphs feedon leaves using their sucking mouthparts. Once theybegin to feed, the nymphs move very little. Thenymphal period lasts about 2 weeks, and a generationcan be completed in about 4 weeks. There are severalgenerations per year, and this insect can grow year-round in greenhouses.

ManagementThe best control method is to prevent the introductionof this pest through sanitation and exclusion. Becauseof the high level of damage that even low numbers oftomato psyllids can cause, the tolerance level for thispest is quite low. Insecticides can be used to eliminateinfestations if they do occur.

Insecticides for Tomato Psyllid Control Pyrethrins

This pest is susceptible to contact sprays ofpyrethrins, but make two applications at 7-day inter-vals. Spinosad is not specifically labeled for psyllids,but it is labeled for tomatoes and has given high levelsof control of tomato psyllids in some trials.

ThripsWestern flower thrips Frankliniella occidentalisTobacco thrips Frankliniella fuscaOnion thrips Thrips tabaciSeveral other species

Thrips are tiny insects, less than 1/16 inch, thatfeed on plant leaves, blooms, and fruit with “punchand lap” mouthparts. There are several differentspecies of thrips, but western flower thrips, onionthrips, and tobacco thrips are the most common.Although they don’t often occur in greenhouse toma-toes in large enough numbers to cause serious injury,thrips are important pests because they can vectortomato spotted wilt virus (TSWV). Thrips can scar anddistort fruit by feeding on young fruit.

BiologyThrips reproduce on a large number of crops andweeds, many of which serve as hosts of TSWV. Theeggs, which are inserted into plant tissue, hatch intoelongate, spindle-shaped larvae. They begin feedingon the undersides of leaves by puncturing cells withtheir ice pick-like mandible and lapping up the result-ing plant fluid. The larvae feed in this fashion for 8 to12 days before moving to the ground, finding a pro-tected location, and entering the pupal stage, whichlasts 3 to 7 days. Adult thrips, which have fringedwings, return to host plants to feed in the same man-ner as the larvae and to deposit eggs. Although theyare small and are relatively weak fliers, adult thripsare easily windblown and can migrate long distances.Adult flower thrips often gather in blooms where theyfeed on pollen. Immature thrips become infected withTSWV when feeding on infected plants. Migratingadults remain infected for the rest of their lives andspread the virus to other hosts.

ManagementBecause they can vector TSWV, exclusion and sanita-tion are the best methods of controlling thrips. Butbecause of their small size, you need very fine meshscreening to exclude thrips. Screening and other exclu-sion practices will also prevent entry of other green-house insect pests. Blue or yellow sticky cards are use-ful monitoring tools. Blue is more attractive to thrips,but yellow cards attract a wider range of pests, includ-ing thrips.

Be careful to avoid bringing thrips or TSWV-infested plants into the greenhouse. It is also impor-tant to control and prevent the growth of broadleafweeds around the greenhouse because these weedscan serve as hosts for both thrips and TSWV. Wheninsecticide treatment is needed, contact insecticidessuch as spinosad or malathion can provide effectivecontrol. Other control options such as Beauveriabassiana may be more compatible in greenhouseswhere you use biological control. Several species ofpredatory mites prey on immature thrips.

Insecticides for Thrips ControlAzadirachtin, Beauvaria bassiana, chlorfenapyr,malathion, paraffinic oil, potassium salts of fatty acids,pyrethrins, spinosad.

Although spinosad is mainly used to control cater-pillar pests, it is also one of the best products for thripscontrol. Malathion, paraffinic oil, potassium salts offatty acids and pyrethrins provide contact control ofthrips. Azadirachtin is a botanically derived insectgrowth regulator. Beauvaria bassiana is a biopesticidemainly used to control whiteflies, but it also providessome control of thrips.

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LeafminersVegetable leafminer Liriomyza sativaeSerpentine leafminer Liriomyza trifolii

Leafminers feed on a variety of weeds and veg-etable crops, including tomatoes. In the field, naturallyoccurring parasites and predators often keep leafminerpopulations in check. However, leafminers can be sig-nificant pests in greenhouses because the naturallyoccurring parasites and predators are excluded. Theleafminers most commonly encountered in greenhousetomatoes are vegetable leafminers, Liriomyza sativae,and serpentine leafminers, Liriomyza trifolii. Adults ofboth species are small flies, about 1/12 inch long, thatare black with yellow markings. Their overall appear-ance is similar to that of fruit flies. Damage is causedby the larvae, which mine in the leaves, causing wind-ing or blotch-shaped mines that reduce leaf area andinterfere with translocation within the leaf. These pestsnever attack the fruit directly. Although light infesta-tions (one to two mines per leaf) have little negativeeffect, heavy infestations can decrease functional leafarea and overall productivity. However, because heavyinfestations are usually found in the lower portion ofthe plant, yield effects are less than they would be ifyoung leaves were attacked.

BiologyBecause leafminers prefer to deposit their eggs inmature leaves, egg laying is concentrated in the middleand lower parts of the plant. The female flies inserttheir eggs into the leaf tissue individually. A femalemay lay several hundred eggs during her lifetime. Theeggs hatch in about 3 days, and the small larvae beginfeeding between the upper and lower leaf surfaces, cre-ating narrow, winding mines. As larvae grow, thewidth of the mines increases and mines often becomeblotch-shaped. Depending on temperature and otherenvironmental conditions, the leaf-mining stage lasts 5to 12 days. Larvae then emerge from the leaf to formyellowish-orange, oval-shaped pupae, which usuallyroll off the foliage onto the ground. A new generation isproduced about every 23 days, but there is usuallygreat overlap of generations in greenhouse infestations.

ManagementPruning lower leaves is a standard production practicethat helps control diseases as well as leafminers. Butyou need to promptly remove pruned leaves from thegreenhouse. Plastic sheets placed over the surface ofthe growing medium can prevent pupae from fallingin the growing media, where survival is higher, andcause them to roll into the aisle where they can beswept or vacuumed. Diglyphus isaea and Dacnusa siberi-ca are two species of parasitic wasps commonly usedfor biological control of leafminers.

Insecticides for Leafminer ControlAzadirachtin, pyrethrins, spinosad.

Although spinosad is mainly used to controlcaterpillar pests, it also has activity against leafminers.Malathion and pyrethrins are used to control adultleafminers.

Because they are protected inside the leaf, larvalleafminers can be difficult to control. Leafminers oftenquickly develop resistance to insecticides after repeat-ed exposure.

Fungus Gnats Bradysia spp.Fungus gnats are small, dark, mosquito-like flies

that are less than 1/8 inch long and have long, beadedantennae. The adults are relatively harmless. The lar-vae feed on fungi in the growing medium as well ason roots and root hairs, and heavy infestations of lar-vae can cause enough root pruning to interfere withnutrient uptake. The larvae are slender and clear witha black head capsule and may be up to 1/5 inch longwhen fully mature. These pests are most abundant inthe winter and spring.

BiologyAdults gather in moist, shady areas where they laytheir eggs in strings of 3 to 40 on the surface of thegrowth medium. Eggs hatch within 3 - 6 days, and lar-vae begin feeding on fungi, root hairs, and roots.Larvae mature in about 2 weeks, construct a pupalcase, and remain there about 3 - 7 days before emerg-ing as adults. Adults live about 1 week, and femalescan lay more than 100 eggs during this period.ManagementUse yellow sticky traps placed near the growing medi-um at the base of the plants to monitor for fungusgnats. Practice good water management to avoid accu-mulations of moisture. Fungus gnats can also be con-trolled using biological agents, such as the soil-dwelling predatory mite Hypoaspis miles, or the insect-infecting nematode Steinernema feltia.

Insecticides for Fungus Gnat ControlAzadirachtin, B.t. israelensis, malathion, pyrethrins.

The best way to control fungus gnats is to usemedia drenches to control the larvae. Treatments con-taining azadirachtin or Bt israelensis can be used asmedia drenches. Foliar sprays of short-residual insecti-cides, such as pyrethrins or malathion, can provideshort-term reductions of adult numbers, but they willnot control larvae and will not be effective as stand-alone treatments.

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Spider MitesTwo-spotted spider miteTetranychus urticaeSeveral other species

Spider mites are not insects but tiny, eight-leggedpests that feed on the undersides of leaves. Althoughspider mites are visible with the naked eye, it takes a10X or higher power hand lens to really be able to seethese pests. Damage is caused by both adults andimmatures, which feed on the undersides of theleaves, removing sap and causing the leaves to becomediscolored. Where populations are heavy, they cancause leaves to drop off. There are several differentspecies of spider mites, ranging from light green tored. Two-spotted mites are probably the most commonspecies and are also one of the most difficult to control.

Spider mites are most likely to reach damagingpopulations under hot, dry conditions. Initial signs ofinfestation are leaves that look stippled. Close exami-nation of the undersides of leaves with a hand lenswill reveal all stages of mites and eggs. When infesta-tions are heavy, a fine webbing of silk will often bepresent, and mites may be found on the upper surfaceof the leaves.

Infestations often begin in isolated spots withinthe greenhouse, and prompt application of spot treat-ments will often prevent spread to the remainder ofthe house. Although they are wingless, mites can easi-ly spread throughout the house on workers perform-ing normal maintenance operations, such as pruningor harvesting. Mites can also be brought into thegreenhouse on the clothing of workers or on plantsthat are brought into the greenhouse.

BiologyEggs are deposited on the undersides of leaves wherethey hatch into six-legged immatures known as larvae.These begin feeding on leaf tissue and soon molt intoeight-legged nymphs. The nymphs then develop intosexually mature adults. The rate of development isstrongly influenced by temperature and other environ-mental conditions, but under optimum conditions,two-spotted spider mites can complete a generation inas little as 5 to 7 days. Adult females may live 1 to 2weeks and deposit up to 100 eggs per female.

ManagementBecause populations of spider mites can develop onmany other species of plants, good sanitation practicesare a key to avoiding infestations. Control broadleafweeds around the outside of the house, and do not let weeds grow inside the house. Severalspecies of predatory mites, such as Phytoseiulus persimilis, are available for use in biological controlprograms.

Miticides for Spider Mite ControlBifenzate, chlorfenapyr, paraffinic oil, potassium saltsof fatty acids.

Specific miticides, such as bifenzate or chlorfenapyr ,usually give best control.

Tomato Russet Mites Aculops lycopersiciTomato russet mites are much smaller than spider

mites and can only be seen easily under a microscopeor through a strong hand lens. Adults are about 0.2mm long and are yellow, cigar-shaped creatures withtwo pairs of legs located near the larger, head end.These mites belong to the family known as eriophyi-dae and differ greatly from spider mites, which belongto the family tetranychidae. Because these mites are sodifficult to see with the unaided eye, the damage theycause is often mistaken for disease or nutritional defi-ciency. As their name implies, injury symptoms areleaf and stem russeting or bronzing and leaf curling.The leaf curling is due to the large numbers of tinymites feeding on the leaves. This pest attacks field-grown tomatoes in the southern areas of the countrywhere warm conditions allow continuous survival offavorable hosts. However, tomato russet mites can sur-vive and reproduce throughout the country in green-house-grown tomatoes.

BiologyTomato russet mites are wingless, but they spread bywind and are carried on clothing, birds, or insects.They have a narrow range of host plants, but they alsooccur on other solanaceous crops, such as eggplantand pepper, as well as on solanaceous weeds, such asnightshades and jimson weed. Eggs are deposited onthe surfaces of leaves and stems, where they hatch intotiny nymphs that immediately begin feeding andquickly grow to adults. They can complete a genera-tion in as little as 7 days.

ManagementSanitation is the key to avoiding infestations of tomatorusset mites. Do not allow weeds or volunteer plantsto grow in greenhouses between crops because thesecan serve as hosts. Likewise, maintain good control ofweeds, especially solanaceous weeds, in the outsidearea around the greenhouse, and do not allow poten-tial host plants to be brought into the greenhousewhen a crop is being grown.

Miticides for Tomato Russet Mite Controlchlorofenapyr

Sulfur is one of the products traditionally recom-mended for chemical control of tomato russet mites,but more specific miticides, such as chlorfenapyr, pro-vide better control.

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Tomato PinwormsKeiferia lycopersicellaThese insects are important pests of field-grown

tomatoes in subtropical growing areas, but they canpotentially occur in greenhouse tomatoes throughoutthe country. Pinworms are tiny caterpillars that areonly 1/4 inch long when fully grown. Despite theirsmall size, these caterpillar pests can cause seriousfruit injury. The caterpillars are yellow, gray, or greenwith purple spots and a brown head. Adults are small,gray moths that are about 1/3 inch long and generallyare active at dusk.

BiologyThe tiny eggs are usually deposited on the leaves insmall clusters. Upon hatching, the tiny larvae bore intothe leaf and feed as leafminers, causing white, blotchymines. After they grow too large to live within the leaf,the larvae fold a leaf or web two leaves together to cre-ate a protected environment where they continue feed-ing. Older larvae also feed by boring into the stem endof developing fruit, causing small, pinhole-likewounds, and this direct fruit injury can cause seriousfruit loss unless infestations are quickly found andcontrolled. Mature larvae exit the infested fruit or leaffolds and usually drop to the ground to pupate.

The life cycle from egg to adult varies but aver-ages about 30 days in the summer and 40 to 55 days inthe winter. Tomato is the preferred host, but this cater-pillar also attacks eggplant and potato, as well as somesolanaceous weeds.

ManagementUse pheromone traps to monitor for the presence ofpinworm infestations. Proper use of traps providesearly detection. Sanitation and exclusion are alsoimportant components of pinworm management. Besure to keep the greenhouse free of volunteer hostplants, including solanaceous weeds, during nongrow-ing periods, and use screening to help exclude moths.Avoid introducing infested plants into the greenhouse,and promptly remove and destroy infested leaves andcull fruit. Hand removal of infested leaves can be espe-cially helpful in slowing the growth of very low infes-tations. Moths are attracted to light traps, and lighttraps can be useful control tools when populations arelow. Mating disruption through the use of slow-releasepheromone dispensers or microencapsulatedpheromone sprays is a useful, noninsecticidal methodfor controlling pinworms.

Insecticides for Tomato Pinworms ControlSpinosad, cholorfenapyr

Specific caterpillar insecticides, such as spinosador chlorfenapyr, provide best control when treatmentis necessary, but repeated applications will usually beneeded to control an established infestation. Because

of their protected feeding environment, Bt productsare usually not used against pinworms.

Large CaterpillarsTomato fruitworm Helicoverpa zeaArmyworms Spodoptera spp.Cabbage looper Trichoplusia ni

There are several species of large caterpillars (over1 inch long when fully grown) that sometimes infestgreenhouse tomatoes. These infestations are most like-ly during the fall after large numbers of moths havedeveloped on field crops. Because a single female canlay several hundred to over 1,000 eggs, it only takes afew female moths getting into the greenhouse to causea serious infestation.

Common Species of Large CaterpillarsTomato fruitworms: Tomato fruitworms are one of

the most significant insect pests of field-grown toma-toes. They are less common in greenhouses, but wheninfestations do occur, they can cause serious losses.This is because, as their name implies, this caterpillarfeeds directly on the fruit. This insect attacks manyother crops and is also known as the cotton bollworm,corn earworm, or soybean podworm. These are stout-bodied, green or brown striped caterpillars about 11/2 inches long when fully grown. The moths are buffbrown with a small brown spot on each forewing.

Tomato fruitworms feed on blooms, as well asimmature and ripe fruit. The individually laid eggs aremost often deposited on leaves near upper bloom clus-ters. If not controlled, heavy infestations of these cater-pillars can destroy more than half a crop. Becauselarge larvae that have already bored into fruit are verydifficult to control, it is important to detect infestationsand begin treatment when caterpillars are small (lessthan 1/4 inch long). Tobacco budworm is a smiliarspecies that also attacks tomatoes.

Armyworms: Several different species of army-worms occur in greenhouse tomatoes. Fall armywormsvary from light tan or green to nearly black. They havea distinct inverted white Y-shape on the front of theirheads. Their bodies have a greasy appearance andmay be up to 2 inches long. Beet armyworm, yellow-striped armyworm, and southern armyworm are someof the other species that are sometimes found ongreenhouse tomatoes. All species of armyworms aremainly foliage feeders, but will occasionally damagefruit. Because armyworms lay their eggs in large mass-es, heavy infestations may occur in isolated areas with-in the greenhouse, and timely spot treatments canoften provide effective control.

Cabbage Loopers: Loopers are pale-green caterpil-lars with only two pairs of abdominal prolegs (army-worms and tomato fruitworms have four pairs). Thiscauses them to move in a “humpbacked” or loopingfashion. They have light stripes down their backs and

8

are up to 1 inch long. Cabbage loopers are leaf feedersand rarely attack fruit, but they are one of the moredifficult caterpillars to control. Cabbage looper mothsare gray with a silver figure eight or octopus-shapedmark on each forewing.

BiologyEggs are deposited by female moths that have madetheir way into the greenhouse. Tomato fruitworm andlooper moths lay their eggs individually, but army-worm moths lay their eggs in large masses. Eggs hatchwithin 3 to 7 days, depending on species and tempera-ture. The small caterpillars begin feeding on leaf tis-sue. The caterpillar stage lasts about 11 to 17 days withlarvae eating more and causing proportionally moredamage as they become larger. Caterpillars eat about80 percent of their total food consumption during thefinal three days of their larval period. This is why seri-ous injury often appears to occur overnight. Uponcompletion of its larval development the caterpillarforms a pupa on the foliage or in the soil, dependingon species. Moths may emerge from these pupae in aslittle as 8 to 11 days. However, some species overwin-ter as pupae.

ManagementBecause of their size, the moths that produce thesecaterpillars are easy to exclude from greenhouses(even regular window screening is sufficient), and seri-ous infestations are rare in houses with good exclusionpractices. Because large caterpillar pests don’t ofteninvade the greenhouse, biological controls are rarelyused on them.

Insecticides for Large Caterpillar ControlB.t. kurstaki, chlorfenapyr, spinosad

Specific caterpillar treatments, such as spinosad,provide good control when applied in a timely andappropirate manner. Chlorofenapyr will contol leaf-feeding caterpillars but is less effective against tomatofruitworms. Foliar-applied Bt sprays are most compat-ible with biological control programs, but because theyare slow-acting, these must be applied when caterpil-lars are small.

SlugsSeveral species

Slugs are soft-bodied, gray or mottled, slimy crea-tures measuring up to 4 inches long. They are unrelat-ed to insects, and their bodies are covered by a thick,slimy mucous. They can occasionally become seriouspests in greenhouses. Slugs feed on molds, decayingorganic matter, and the foliage of plants. They musthave a moist environment, and they prefer darkness.Ideal habitats include under boards, trash, and otherdebris and in crevices. Slugs are active at night andleave a shiny, slime trail. These trails can be seen onfoundation walls, floors, walkways, and plant leaves.

ManagementSlugs are best controlled by eliminating their hidingplaces. This involves removing boards and otherdebris left on the ground and maintaining good weedcontrol. Heavy growths of weeds can provide goodhiding places for slugs, whether inside the greenhouseor around the outside of the house.

Molluscides for Slug and Snail ControlIron phosphate, metaldehyde.

Slugs can be controlled with specially formulatedbait treatments containing iron phosphate or metalde-hyde. Because these are pellets or are granular prod-ucts that are not applied directly to the plants, thesetreatments are compatible with biological control pro-grams. Metaldehyde is poisonous to pets and wildlife,so be sure to follow label directions.

9

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There are 43,560 square feet in one acre, or about 44,000 square feet. You can convert amount per acre to amount per 1,000 square feet by dividing by 44. For example, 10 fluid ounces per acre = 10

divided by 44, or 0.23 fluid ounces per 1,000 square feet.

When measuring small amounts of liquid, it is easier to measure in milliliters rather than fluid ounces. There are about 29.6 milliliters in one fluid ounce. Thus 0.23 fluid ounces per 1,000 square feet =

0.23 multiplied by 29.6, or 6.8 milliliters per 1,000 square feet. There are about 5 milliliters per teaspoon.

When measuring small amounts of dry products, it is easier to measure in grams, rather than ounces. Small digital scales that will accurately measure grams and fractions of grams can be purchased

for less than $100. There are 28.35 grams in one ounce.

Thus 0.38 pounds per acre = 0.38 multiplied by 16 ounces per acre, or 6.08 ounces per acre. 6.08 multiplied by 28.35 = 172 grams per acre. 172 divided by 44 = 3.9 grams per 1,000 square feet.

Disease Identification and ManagementTo develop a greenhouse tomato disease managementprogram, you must know the diseases that affect thecrop and the conditions that can cause problems.

Greenhouse tomato diseases show their symptomson roots, stems, leaves, and fruit. While some symp-toms are common to several diseases, it is usually pos-sible to identify the more common fungal and bacterialdisorders by their symptoms. However, some virusdiseases may be more difficult to identify. If you havetrouble identifying a disease, bring specimens to yourcounty Extension office, or mail them to a plant dis-ease diagnostic lab. Before sending a sample for analy-sis, check with your county Extension agent about thecorrect method of sample collection and packaging.Include helpful information, such as recent applica-tions of pesticides, periods of extreme humidity, andother details that could be useful for an accurate diag-nosis.

Looking for one key symptom helps most growersidentify the disease that has infected the crop. Do nottry to remember all symptoms that could be producedby a given disease. Scout plants for those diagnosticfeatures characteristic for a given disease; thisimproves the accuracy of disease determinations andmanagement steps necessary for its control. Key symp-toms described for each of the following diseases willhelp identify diseases that could occur in the crop.

Disease Identification

Fungus DiseasesBotrytis gray mold (Botrytis cinerea) is probably

the most common and troublesome disease in green-house tomatoes since resistant varieties are not avail-able and the fungus is present in all greenhouses.Infection by the gray mold fungus occurs when therelative humidity is 90 percent or higher. All plantparts can be invaded. Plants are generally more vul-nerable during fruit bearing.

Key symptom: Look for light-tan or gray spots oninfected leaves. These areas become covered by abrown or gray fuzzy mass of fungus growth, and theleaf collapses and withers. Other sites of infectioninclude dying flowers and the calyx area of fruit. Fromthe calyx, infection proceeds into fruit which quicklybecomes water-soaked and soft. Under a hand lensyou can see spore-bearing structures that look likebunches of grapes on the infected tissue. Since thecausal fungus does not actively attack healthy tissue,stem invasion occurs through branch stubs resultingfrom pruning or other injured sites along the stem. Thetan cankers that form along the stem may be large andoften cause early plant death. Under humid condi-tions, distinct masses of fungus growth form on cankersurfaces. Leaf mold (Fulvia fulva) was a common and severeproblem in the early 1970s because resistant varieties

were not available. Today, most modern varieties havecomplete resistance (C5) to all races of the leaf moldfungus (refer to the “Disease Management” section inthis publication). Varieties with incomplete resistance(C2) are often affected by leaf mold under humid con-ditions. Scout these varieties frequently for earlysymptoms of this disease. Infection by the leaf moldfungus occurs when relative humidity remains at 90percent or higher for several hours. This disease isfavored by the same conditions that encourage graymold development. Leaf mold symptoms begin onlower, older leaves but progress to younger foliageover time.

Key symptom: Look for pale-green or yellowishareas with irregular margins on upper leaf surfaces.Beneath the yellow spots, areas of olive green velvetgrowth are visible. Infected leaves become yellow-brown and drop prematurely. Defoliation progressesup the plant.

Early blight (Alternaria solani) sometimes causes prob-lems in greenhouse tomatoes. Symptoms appear onleaves, stems, and fruit.

Key symptom: Look for characteristic circularbrown leaf spots, up to 2 inches in diameter. Spotscontain dark rings with a common center, giving a tar-get-board appearance.

Powdery mildew (Erysiphye sp.) is not a widespreadgreenhouse tomato problem in Mississippi, but it is afungus disease that is becoming more common.

Key symptom: Powdery mildew is identified bywhite patches of fine, powdery growth on the uppersides of leaflets. Patches are up to 2 inches in diameterand generally appear on the oldest foliage. Severecases weaken the plants and lead to lower yields.

Target spot, another fungus disease (Corynespora cassi-icola), has recently become widespread in greenhousetomatoes across the state. Early symptoms of targetspot first appear on foliage.

Key symptom: Look for small, water-soaked spotson the upper surface of older leaves. The spots rapidlygrow to form light- to dark-brown circular lesions witha common center. The rings resemble the target-spotsymptoms associated with early blight. Lesions alsoform on leaf petioles and stems.

Large numbers of target-spot spores occur oninfected leaves and stems, and some of these aredeposited onto surfaces of young fruit that becomeinfected during humid conditions. Within severaldays, fruit symptoms appear as sunken, pinpoint-sized, brown lesions. These enlarge and develop intocrater-like spots that continue to grow and will crackopen as fruit ripens. Growers need to be aware of tar-get spot because this disease may quickly move fromfoliage to fruit, causing a large reduction in the yieldof marketable fruit.

13

Pythium root rot (Pythium spp.) is becoming anincreasingly severe problem in Mississippi greenhous-es. The species of this fungus that cause problems inthe crop are easily introduced into the greenhouseenvironment via soil clinging to shoes, tools, and,often, contaminated water supplies. A common sourcethat causes Pythium is a nonsterile growth medium(such as river sand piled on bare ground) where itbecomes contaminated from underlying soil under wetconditions. Pythium root rot shows up most oftenwhen too much water accumulates around roots.Pythium is a water mold fungus and is most aggres-sive when the growth medium used is too heavy, andbags or other containers don't drain well. When thisoccurs, the fungus attacks juvenile roots and eventual-ly the main root mass.

Key symptom: Look for large areas of chocolatebrown or black roots on wilted, stunted plants withyellow, weak foliage. Infected plants generally do notdie and often produce new roots if you correct mois-ture problems. Send intact root systems from suspectplants to a plant disease clinic for examination ifsymptoms are not clear.

Fusarium crown and root rot (Fusarium oxysporum f.sp.radicis-lycopersici) was first found in Mississippi green-house tomatoes in the late 1980s. This disease is almostimpossible to control without the use of resistant vari-eties. Growers in greenhouses where this has beendetected need to learn symptoms of the disease andpractice proper variety selection.

The FCRR fungus, after initially infecting second-ary roots, moves into larger roots and eventuallyinvades the plant's vascular system. Symptoms ofFCRR include stunted growth and wilting on sunnydays, especially if plants have heavy fruit loads.Infected plants may die after repeated wilting. To diag-nose whether a plant has FCRR or Pythium root rot,cut the base of the stem lengthwise.

Key symptom: Look for dark to reddish-browndiscoloration of the vascular tissues. Discoloration isevident up 12 to 18 inches above the soil line, in con-trast to Fusarium wilt, where discoloration may extend3 to 4 feet high.

Timber Rot or White Mold (Sclerotinia sclerotiorum) isa fungal disease that is being seen more frequently inMississippi greenhouse tomatoes. Lesions on the lowerportion of the stem can result in rapid plant death.

Key symptom: Initially look for a water-soakedlesion forming on the stem of the plant, usually closeto the floor and within 2-3 feet of where the stem goesinto the growing medium. A white fungal growth maybe seen on the stem. The white color of the fungalmycelium is what distinguishes timber rot from graymold. Plants turn yellow on top, wilt, and die quicklyfollowing infection. If you cut through the lesion onthe stem, you will likely find hard, black rock-likestructures inside. These rock-like structures, called

“sclerotia,” fall to the floor and serve as a source forinfection in the next season’s crop.

Bacterial DiseasesPlants affected by bacterial wilt (Pseudomonassolanacearum) rapidly wilt and die without yellowingor showing leaf necrosis. When a wilted plant is cutnear the soil line, the inside of the stem looks dark andwater-soaked. However, these symptoms are notalways easy to detect.

Key symptom: Examine a cross-section of thelower stem for sap to squeeze out when the stem ispressed. In late stages, the stem may become hollow. Test suspicious plants for bacterial wilt. The method issimple, and you can get results in 2 to 5 minutes.Follow these steps:

- Cut a 2-inch-long section from the base of the stem. - Fill a small, clean glass container with tap water. - Suspend the stem (using a wire hanger or other object) about 2 inches into the water. Key symptom: Look for a thin, milky stream of

bacterial cells to appear about 2 to 5 minutes after put-ting the stem in the water. You see the streaming bestwhen the container is at eye level, with the light com-ing in from behind.

Pith necrosis (Pseudomonas corrugata) is sometimesreferred to as bacterial hollow stem. Affected plantssometimes wilt and show a slight yellowing of lowerfoliage.

Key symptom: On lower stems, look for brown,sunken, necrotic (dead) stem cankers. Lengthwise cutsthrough cankers reveal hollow stems, a symptom ofthe disease.

Virus DiseasesTomato mosaic virus (ToMV) was an important dis-ease until the introduction of resistant varieties in theearly 1980s. Today, most modern varieties are resistantto ToMV, a strain of Tobacco Mosaic Virus (TMV), andthis disease is no longer a major threat to production.However, growers who use vulnerable varieties needto become familiar with ToMV in case the diseaseshows up and plant removal becomes necessary.

ToMV diagnosis may be difficult. Symptomsdepend on variety, age of plant at time of infection,and environmental conditions. Plants become stunted,leaves may have mild to severe yellow-green spots,crinkles, ridges, strings, or curls. Stems may developstreaks of dead plant tissue. Generally, fruit shows nosymptoms, although severe strains may cause internalbrowning, pitting, or severe mottling.

Because of the wide array of possible symptoms,there are no key symptoms to look for. Because ToMVspreads so easily through pruning, fruit harvesting,and other routine activities, when you suspect the dis-ease you need to get an accurate diagnosis. Send speci-mens to a disease clinic for testing or microscopic

14

examination for the presence of virus-inclusion bodies.Remove diseased plants promptly.

Tomato spotted wilt virus (TSWV) can be a wide-spread problem in greenhouse tomatoes. Like ToMV,diagnosis of TSWV in greenhouse tomatoes can be dif-ficult. Symptoms can be many and varied. TSWVsymptoms can be confused with those caused by otherviral, fungal or bacterial pathogens, or nutritional dis-orders. One of the chief vectors of the virus, theWestern flower thrips (several other thrips species arealso known to transmit the virus), is widespreadacross the Midsouth. Scouting for and controllingthrips populations is important to prevent the spreadof TSWV. Many weedy plants can harbor the virus, sokeep a weed-free perimeter around the greenhouse.Test kits are available to check for the presence ofTSWV in tomato. The immunostrip test kits are inex-pensive, dependable, and easy to use. Contact yourcounty Extension office to find out where to buy testkits.

Key symptom (or at least suspect TSWV): Look forsmall, dark-brown leaf spots in the upper portion ofthe plant, which may be arranged in a "ringspot" pat-tern, dark streaking in petioles and stems, stuntedgrowth terminals, and brown or black lesions on dis-torted fruit. Submit samples of suspicious plants toyour Extension plant disease diagnostic lab. Removesuspect plants.

Tomato Yellow Leaf Curl Virus (TYLCV) was firstobserved in Mississippi in greenhouse tomatoes in2001. This destructive virus disease is transmitted bywhiteflies. Once infection occurs, the virus preventsfurther plant development. No flowers or fruit are pro-duced from that point on resulting in a total crop loss.

Key symptom: Symptoms begin showing upabout 10-12 days after feeding of whiteflies that carrythe virus. Leaves in the top of the plant will developinterveinal chlorosis (yellowing between the veins),and the sides of the leaves will curl upward. Theleaves may look crinkled. The symptoms will be subtleat first, but yellowing will increase over time andbecome very noticeable. Scouting for and controllingwhiteflies are important methods of preventing furtherspread of the virus. Commonlygrown Mississippi greenhousetomato varieties do not haveresistance to this disease.

MiscellaneousDiseasesDepending on your location,other diseases could presentproblems to your crop. Forexample, Cercospora leaf spot,bacterial spot, speck, andcanker are detected in green-house tomatoes from time to

time. Ask your Extension agent for help in diagnosingdiseases that do not fit the "key symptom" approach.

Disease ManagementDiseases caused by fungi, bacteria, and viruses canquickly destroy a crop of greenhouse tomatoes whenconditions are favorable. However, if you use a combi-nation of recommended practices (IPM), you can man-age diseases. Biological, cultural, sanitary, and chemi-cal techniques are necessary, since no single practicecontrols all diseases affecting the crop.

Biological ManagementBiological management is the most economic andeffective method of handling several significant dis-eases. Biological disease management mainly involvesusing varieties with disease resistance. Compared tothe 1970s when the commonly grown varieties did nothave disease resistance, most modern greenhousetomato varieties are resistant to one or more diseasesthat used to be limiting factors in production.

Cultural ManagementCultural management refers to practices connected tothe production of the crop. This method creates condi-tions that do not favor disease development.

Regulating greenhouse relative humidity is criticalsince moisture is the main factor influencing plantinfection by the fungi responsible for gray mold, tim-ber rot, and leaf mold. Relative humidity must beabove 90 percent for spore germination and infectionto occur. Most bacterial diseases also need high, rela-tive humidity.

Control of relative humidity is particularly impor-tant when greenhouses are tightly sealed to conserveenergy. During warm fall and spring days, the airinside the greenhouse picks up moisture, since warmair holds more moisture than cool air. As the air coolsin the evening, the moisture-holding capacity dropsuntil the house reaches the dew point and moisturebegins to collect on surfaces. Eliminate moisture con-densation by three methods:

Keep the ventilators open 1 inch or so (orexhaust fans on low capacity) when the heatcomes on in the late afternoon. Cold air enters the

15

Variety Disease resistanceCaruso

CapelloDombelloPerfectoLaura

DombitoJumboMatch

SwitchTrustBlitz

Tomato Mosaic Virus(ToMV)ToMVToMVToMVToMVToMVToMV

ToMV

ToMVToMVToMV

C2 (Leaf MoldRaces A and B)C2C2

C5 (Leaf mold RacesA, B, C, D, and E)C5C5C5

C5

C5C5C5

Fusarium crown androot rot (FCRR)FCRRFCRRFCRR

house while warm, moist air leaves. The cold,drier air entering is heated or further dried. Then,after 5 to 10 minutes, the ventilators are closed orfans turned off. Warm, dry air now exists in thegreenhouse. Moving air in the greenhouse helps reduce

moisture on plant surfaces. The horizontal airflowsystem or the overhead polyethylene ventilationtube system keeps temperatures steady anddecreases cold spots where condensation is likely. When a greenhouse is very moist, you may need

to exchange the air one or more times during thenight. Greenhouse supply companies sell controlsthat turn on the fans at programmed times duringthe night.

Temperature control is also important. For exam-ple, greenhouse temperatures no lower than 70degrees limit development of gray mold. FCRR andPythium root rot thrive in cooler temperatures as well.

Pith necrosis appears to be most severe whenplants are overfertilized with nitrogen. It is likely thatPythium root rot could be more of a problem if rootsare injured by high soluble salt levels.

Pruning methods may make stems more vulnera-ble to gray mold infection since fewer stem lesionsdevelop when you cut or break petioles close to thestem than when you remove them 1 or 2 inches fromthe stem.

Sanitation ManagementMost growers view sanitation as an important part ofeffective disease management. Unfortunately, not allgrowers carry out a strict sanitation routine. Before beginning a new crop:

Rid the greenhouse of debris that could spread adisease in the future from fungi, bacteria, orviruses. If diseases were a problem in the previous crop,

think twice about reusing old growth containers.Do not reuse growth containers (such as rockwoolslabs and poly bags) or growth medium fromwhich diseased plants were removed. For aNutrient Film Technique (NFT) system or modi-fied NFT system, use bleach or another suitabledisinfectant before new crop installation.Completely flush the system following treatmentto remove disinfectant that could be poisonous toplants. Disinfect the greenhouse by spraying all sur-

faces with a 5- to 10-percent solution of householdbleach. You can get this mixture by adding 1 gal-lon of bleach to 19 gallons of water (5 percent), or1 gallon of bleach to 9 gallons of water (10 per-cent). After about 15 minutes, rinse sprayed sur-faces with plain water. This treatment is effectivefor most greenhouse disease microorganisms, butyou must use it in combination with a strong sani-tation program.

If you produce your own transplants, use dis-ease-free seeds, sterile growth media, and contain-ers. Remove and destroy transplants that do notlook normal.

After crop installation: Have a clean-up room to disinfect hands and

clean shoes. In short, use any practice available toprevent introducing diseases into the greenhouse. Restrict use of tobacco products if you are grow-

ing a ToMV-susceptible variety. Frequently disinfect tools and other equipment

with bleach at the rate of 2 gallon per 10 gallons ofwater. Dip for 5 to 10 seconds, drain, and usewithout rinsing. Keep a "clean strip" around the outside of the

greenhouse to reduce populations of thrips,aphids, and other insects that could be sources ofvirus introduction. Consider using insect-barrier screens to cut

down on movement (into the greenhouse) ofthrips, aphids, and other possible virus-carriers. Observe plants constantly for any evidence of

disease development. Promptly remove diseasedplants, and remove foliage that may be seriouslydiseased or no longer contributing to plantgrowth. You must destroy diseased plants and dis-eased plant parts or carry them far enough awayfrom the greenhouse so that they won't be a sourceto reintroduce the disease into the greenhouse.

FungicidesThe need for week-to-week fungicide applicationdecreases if you follow these procedures: use sanitarypractices to limit fungus spores that could spread thedisease from previous crops; control the greenhouseenvironment to prevent long periods of high humidity;and use other cultural practices as previouslydescribed.

Many fungicides are now labeled for use on green-house tomatoes. As with insecticides, the new EPAinterpretation of fungicide labels states that if theproduct is labeled for use on tomatoes, and the prod-uct label does not specifically prohibit the use of theproduct in greenhouses, the fungicide can be consid-ered legal to use on greenhouse tomatoes.

Also, you must completely read the product labelbefore use. Some fungicides once labeled for use ongreenhouse tomatoes are no longer legal. One exampleis Exotherm Termil (chlorothalonil smoke bomb). If agrower has an older container with label attached, itwill be labeled for use on greenhouse tomatoes, andthat product would be legal to apply. If the growerrecently purchased a container of Exotherm Termil,they will not find tomatoes on the label. The reason forthis is that an additional chemical was added to theproduct, and this chemical is not labeled for use onany food crop. Thus, a newly purchased container ofExotherm Termil is not legal to apply to greenhousetomatoes.

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Read labels for these products carefully. Each product has tomato on the label and does not prohibit use in a greenhouse. Product labels constantly change to reflect legal

use in greenhouse tomato production. For example, some products have a special use permit only in certain states. You are responsible for determining if the product is

legal in your state. Another concern is the age of the product you are using. For example, Quadris purchased one year ago is legal for use in the greenhouse according to

EPA interpretation of the label. Quadris purchased within the last several months has a restriction specifically stating that the product can not be used in a greenhouse.

REI, Restricted Entry Interval, is time that must pass after an application before workers may enter the treated area.

Personal Preotectivve Equipment, PPE, that must be worn for early entry is specified on the product label.

PHI, Preharvest Interval, is the least amount of time that must pass between the last application of the product and harvest.

Pesticide StorageKeep pesticides where children, adults who are unfa-miliar with pesticides, and animals cannot get tothem. Store all pesticides under lock and key. Do notstore with or near feed, seed, clothing, or other arti-cles. Keep storage areas lit well and ventilated withtemperatures that will not go below freezing. Storein an area that is fire-resistant and has an exhaustfan. Place warning signs on all entrances and keepdoors locked. Store products in their original con-tainers, and mark the month and year of purchase onall packages to determine their age. Keep an up-to-date list of pesticide products.

Worker Protection for Greenhouse EmployeesRead and follow label directions. Use all personal protective equipment (PPE) accord-ing to the label. Use extreme care in enclosed areas. Use a respirator orself-contained breathing device. Ventilate greenhouse properly before reentry. Post reentry periods according to the WorkerProtection Standard. Use proper care and maintenance of personal protec-tive equipment. Inspect gloves for leaks, and washthem off after use and before removal. Know poisoning symptoms for material being used. Work in pairs or have someone check on you andother workers.

By Dr. Blake Layton, Extension Professor, Entomology; and Dr. David Ingram, Associate Extension/ ResearchProfessor, Plant Pathology, Central Mississippi Research & Extension Center

Discrimination based upon race, color, religion, sex, national origin, age, disability, or veteran’s status is a violation of fed-eral and state law and MSU policy and will not be tolerated. Discrimination based upon sexual orientation or group affili-ation is a violation of MSU policy and will not be tolerated.

Publication 1861Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published infurtherance of Acts of Congress, May 8 and June 30, 1914. MELISSA J. MIXON, Interim Director POD rev 01-10

The information given in this publication is for educational and planning purposes only. Because the registration status ofpesticides constantly changes, always read and follow current label directions. Specific commercial products are given asexamples only, and reference to certain commercial products or trade names is made with no discrimination against otherproducts that may also be suitable and have label clearances.