GRAPE, OBSCURE, OR VINE mealybug - - UC Integrated Viticulture Online

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BY Lucia G. Varela, Rhonda J. Smith, Mark Battany, and Walt Bentley University of California Cooperative Extension T hree mealybugs species now occur in wine grape regions of California: grape mealybug ( Pseudococcus maritimus), obscure mealybug (P. viburni) and vine mealy- bug (Planococcus ficus). It is important to distinguish among them because their life cycles are different, and thus chemical control measures (if neces- sary), must be tailored to the specific pest. The recently introduced vine mealybug is spreading throughout the grape growing regions in California. It can reach damaging levels very quickly by contaminating grape clusters with mealybugs, hon- eydew, and sooty mold. North and Central Coast growers have been bat- tling vine mealybug for three to six years respectively and it has been a problem in San Joaquin Valley vine- yards since the mid 1990s. Movement of vine mealybug to new regions has necessitated aggres- sive chemical management and modi- fied farming practices to curtail its spread and the damage it can cause. As a result, vine mealybug has grabbed headlines and become a focus of attention for growers and wineries. A strong effort is underway to detect new vine mealybug infestations early in order to control the insect and prevent further spread, both within the block where it is first discovered and to adjacent vineyards. This extra scrutiny has also increased concerns regarding two other mealybugs that are more com- monly found in vineyards. While searching for signs of vine mealybugs, growers and Pest Control Advisers (PCAs) frequently find grape mealy- bug or obscure mealybug. They now have to recognize the similarities and differences in three species of mealy- JANUARY/FEBRUARY 2006 GRAPEGROWING 1 GRAPE, OBSCURE, OR VINE Which mealybug is it, why should you care? Vine mealybug (planococcus ficus) lifecycle in the north coast Winter Spring Summer Fall Grape mealybug (pseudococcus maritimus) lifecycle in the north coast Winter Spring Summer Fall

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Page 1: GRAPE, OBSCURE, OR VINE mealybug - - UC Integrated Viticulture Online

BY Lucia G. Varela, Rhonda J. Smith, Mark Battany, and Walt BentleyUniversity of California CooperativeExtension

Three mealybugs species nowoccur in wine grape regions ofCalifornia: grape mealybug(Pseudococcus maritimus), obscure

mealybug (P. viburni) and vine mealy-bug (Planococcus ficus). It is importantto distinguish among them becausetheir life cycles are different, and thus

chemical control measures (if neces-sary), must be tailored to the specificpest.

The recently introduced vinemealybug is spreading throughoutthe grape growing regions inCalifornia. It can reach damaginglevels very quickly by contaminatinggrape clusters with mealybugs, hon-eydew, and sooty mold. North andCentral Coast growers have been bat-tling vine mealybug for three to sixyears respectively and it has been a

problem in San Joaquin Valley vine-yards since the mid 1990s.

Movement of vine mealybug tonew regions has necessitated aggres-sive chemical management and modi-fied farming practices to curtail itsspread and the damage it can cause.As a result, vine mealybug hasgrabbed headlines and become a focusof attention for growers and wineries.

A strong effort is underway todetect new vine mealybug infestationsearly in order to control the insect andprevent further spread, both withinthe block where it is first discoveredand to adjacent vineyards.

This extra scrutiny has alsoincreased concerns regarding twoother mealybugs that are more com-monly found in vineyards. Whilesearching for signs of vine mealybugs,growers and Pest Control Advisers(PCAs) frequently find grape mealy-bug or obscure mealybug. They nowhave to recognize the similarities anddifferences in three species of mealy-





Which mealybug is it,

why should you care?

Vine mealybug (planococcus ficus) lifecycle in the north coastWinter Spring Summer Fall

Grape mealybug (pseudococcus maritimus) lifecycle in the north coastWinter Spring Summer Fall

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bugs to correctly identify, monitor andcontrol them.

Origins and need for chemical control

Grape mealybug is native to NorthAmerica and exists in many parts ofCalifornia. It has probably gone unno-ticed in many vineyards and has notcaused economic damage due to lowpopulations. Because it is native, a largecomplex of natural enemies exists andthus it is often under good biologicalcontrol.

Obscure mealybug is an introducedspecies that has been present inCalifornia since the late 1800s. Because itis an exotic pest, it has few natural ene-mies. Obscure mealybug has a narrowertolerance to cold temperatures than thegrape mealybug and is found primarilyin coastal regions. Currently, the largestpopulations of obscure mealybug arefound in the Central Coast.

Vine mealybug is an economicpest of vineyards in the Med-iterranean regions of Europe, Africa,and the Middle East. It has also beenintroduced into South Africa, SouthAmerica, and the southeastern U.S.Vine mealybug has a few natural ene-mies in California that were intro-duced in the 1940s for control of arelated species, the citrus mealybug.

Occasionally, control of grape orobscure mealybug requires chemicalapplication(s). Fruit can becomeinfested with these mealybugs whenpopulations are high, especiallywhen clusters touch older wood onthe vine such as the cordon. In con-trast, vine mealybug infestations canreach much higher population levelsthan grape or obscure and causemore damage to clusters and thevine. At this time, chemical applica-tions are required to control this pest.

Honeydew and ant tendingMealybugs feed on the phloem

and excrete a sugary solution calledhoneydew. Ants are often found inassociation with mealybugs becausethey will feed on the sugary excre-ment. In fact, the ants will tend themealybugs and keep away naturalenemies in order to maximize theproduction of honeydew.

The degree of honeydew produc-tion varies by species and increasesfrom small to significant amounts withgrape, obscure, and vine mealybugsrespectively.

Honeydew can be seen as shiny andsticky areas on leaves, clusters, andtrunks. A wet trunk is an indicationthat a colony of mealybugs is feedingunder the bark and honeydew is seep-ing through the bark. Argentine andgray ants are the most common antspecies that tend mealybugs to obtainhoneydew.

The amount of honeydew visibleon a vine depends not only on themealybug species but also on thenumber of ants tending the colonies.When ants are not present, honey-dew produced by all mealybugs canresult in wet trunks because the antsare not consuming it. Although it ismore common to see wet trunks withvine mealybug infestations, a largepopulation of grape mealybugs inthe absence of ants will also result inwet trunks.

Morphological differencesThe mealybug covers its body with

a waxy secretion that creates a white,mealy appearance in all three species.Wax also accumulates on hairs that

extend around the circumference of thebody, forming white fringe-like fila-ments. The appearance of the white fil-aments distinguish the vine mealybugfrom those in the genus Pseudococcus(grape and obscure mealybug).

GRAPE AND OBSCURE MEALYBUGS:The body shape of the immature andfemale grape and obscure mealybug isrectangular with rounded anterior andposterior ends (Figure I, right). Thehairs surrounding the body are longerthan those of the vine mealybug. Sincethe hairs are longer, the wax accumu-lates more thinly along the length (thefilaments may appear crooked, bent orotherwise irregular).

The waxy filaments in grape andobscure mealybug are longer, thin-ner, slightly less parallel and thushave a more untidy appearance thanthose of the vine mealybug. Morenoticeable are the hairs at the poste-rior end of the abdomen that are con-siderably longer than the ones sur-rounding the rest of the body. Theresult is two to four long, caudal fila-ments that appear as tails.

If the insect is not disturbed, tailsare easily seen in large immatures or inadult females and are the strongestcharacteristic with which to distin-guish Pseudococcus mealybugs from

Table I: Distinguishing characteristics of grape, obscure and vine mealybugs.

MealybugsGrape Obscure VinePseudococcus Pseudococcus Planococcusmaritimus viburni ficus

Body shape Rectangular Rectangular OvalFilaments surrounding body Thin, non-uniform Thin, non-uniform Thick, uniformFilaments posterior end Thin, long Thin, long Thick, shortDefensive fluid Reddish, orange Clear ClearDiapause (dormant period) Yes No NoGenerations 2 2 to 3 4 to 7Synchronized generations? Yes No NoStages overlap No Yes Yesthroughout year?Overwinters under the Upper trunk, Trunk, cordons, Graft union, pruningbark primarily in: cordons, spurs spurs wounds on trunk,

base of spurs. (roots in light soils)

In summer lays eggs Under bark on old Under bark on old Under bark on oldwood, bunches wood, bunches wood, bunches,

throughout the canopyabove the fruit zone

Honeydew production Moderate Moderate to high High

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vine mealybug. It is more difficult tosee the long tails in younger stages,however Pseudococcus immatures canstill be distinguished by the rectangu-lar body shape and by the thin, irregu-larly formed filaments surroundingthe body.

Grape and obscure mealybugs canalso be distinguished from each otherby the color of a defensive fluid theysecrete when threatened. The fluid isexuded as a droplet from pores at theanterior and/or posterior end of thebody. Gently poke the insect with asharp object without puncturing thebody until the fluid is excreted. If the

color of the fluid is reddish orange, theinsect is grape mealybug (Figure II); ifit is clear, then it is obscure mealybug(Figure III).

VINE MEALYBUG: The body shapeof the immature and adult femalevine mealybug is oblong (Figure I,left); wider at the center of the bodyas compared to the anterior and pos-terior ends. The hairs surroundingthe body are short in comparison tothose of Pseudococcus mealybugs.Wax accumulation on the hairsresult in short, uniform, and thickfilaments. The posterior end of theadult female has slightly longer fila-ments than those that surround thebody, but they do not appear as longtails.

Vine mealybug, like obscure mealy-bug, exudes a clear defensive fluidwhen threatened.

Life cyclesGRAPE MEALYBUG has two genera-

tions per year: overwintering and sum-mer generation. This mealybugevolved to live in temperate climateswhere it spends the winter in anarrested state called diapause. Diapauseis a prolonged dormancy regulated byhormones triggered by environmentalconditions. The ability to diapause,and which life stage diapauses, isgenetically determined.

In grape mealybug, the egg is themost resistant stage to cold weather,thus it is this diapausing stage thatoverwinters. The eggs are laid in awhite, cottony egg sac under the barkon the trunk, in the head of the vineor on cordons. Egg sacs are formedwhen the female secretes long waxythreads during oviposition. The cot-tony mass, called an ovisac, concealsthe eggs.

In late winter the youngestnymphs (called crawlers), emergeand, shortly before bud break, theymove from old wood to the spurswhere they gather under the thinbark on one-year-old wood. Afterbud break, a portion of the popula-tion moves to the basal leaves andshoots while the rest remain underthe bark primarily on the upper

portion of the trunk, head, and cor-dons. When high grape mealybugpopulations exist in older vineswith thick bark, they may also befound under the bark much loweron the trunk.

The overwintering generationdevelops through the spring, reachingmaturity in late May and June. At thattime, the adult female returns to the




Figure II. Reddish orange fluid excreted bygrape mealybug (photo: JKC).

Figure I. Vine mealybug female (left) withoval body shape, thick, even (uniform) fila-ments and short tails and grape mealybug(right) with rectangular body shape, thin,slightly unparallel (non-uniform) filamentsand long tails (photo: Jack Kelly Clark).

Figure III. Clear fluid excreted by obscuremealybug (photo: Kent M. Daane).

Figure IV. Vine mealybug colony in the axils of the petiole and cane (photo: MarkBattany).

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old wood to oviposit. Each female lays100 to 300 yellow to orange eggs, thenshe dies. The eggs hatch in seven to 14days.

Summer generation nymphs moveto the shoots, foliage, and clustersthat are touching old wood. Onlyeggs or crawlers are found in lateJune or early July; mostly immaturesare seen through July. Adult femaleswill appear in late summer and earlyfall. Some females will oviposit in thefruit clusters but the majority offemales return to old wood to layoverwintering eggs.

Because grape mealybug has a dia-pausing stage, the life cycle is synchro-nized and the two generations do notoverlap. Thus, at certain times duringthe growing season, specific stages arenot present while others predominate.For example, the lack of females andeggs in mid to late July is a strong indi-cation that the immature mealybugsseen on vines at that time are grapemealybug. Similarly, at bud break,only crawlers along with remainingovisacs are found. When only one ortwo stages of mealybug are present ata given time, the insect is most likelygrape mealybug.

OBSCURE MEALYBUG does not havea diapausing stage, thus it has all lifestages present throughout the year;this distinguishes it from the grapemealybug. It has two to three over-lapping generations per year andoverwinters as eggs inside ovisacsand as nymphs under the bark,mostly on the upper portion of thetrunk or on cordons.

In some central coast vineyards,obscure mealybug has been observed onweeds such as malva during the winterwhen the vines are dormant. After budbreak, a portion of the nymphal popula-tion moves onto new shoots and basalleaves; however, a large number remainhidden under the bark.

In the summer, populations mayincrease dramatically and all stagesare found on above-ground portionsof the vine, specifically under thebark on the trunk, cordons, andspurs; basal portions of the shootsand leaves; and on clusters that touch

older wood. In fall, nymphs migratefrom the canopy to the trunk and cor-dons and remain on old wood underthe bark.

VINE MEALYBUG, like obscuremealybug, does not diapause and alllife stages might be present year-round on a vine. It has several gener-ations per year, depending on tem-perature. In the San Joaquin Valley, itcan have up to seven generations. Inthe cooler North Coast, it has approx-imately four.

During the winter months, eggs,crawlers, nymphs, and matedfemales are found under the bark.The majority of the population isfound on the lower trunk at the graftunion or near the soil line. They arealso found in old pruning wounds onthe trunk, at the crotch in a bilateralcordon-trained vine, or at the base ofthe spur. In light soils present in theCoachella and San Joaquin Valleysand some areas in the Central Coast,they are found on vine roots. This hasnot been seen in the heavier soils ofthe North Coast.

Reproduction slows considerablyin the winter months, and by lateFebruary and March, the majority ofstages found are older nymphs orfully developed females that havenot started laying eggs. In late Marchand early April, overwinteringnymphs develop into adult femaleswhich begin to lay eggs in ovisacs.

When the crawlers of the springgeneration emerge, they move up thetrunk, find a spot to feed and continueto develop. The spring generationdevelops under the bark on trunks andcordons through May and by latespring, nymphs can be found on basalleaves.

In summer, populations canincrease dramatically and all stages ofoverlapping generations are found oncanes, clusters, leaves, and petioleswell above the fruit zone and underthe bark on the trunk, cordons andspurs.

In the canopy, vine mealybug formscolonies in the axils of the petioles andthe cane (Figure IV). Females lay eggs

on all above-ground parts of the vine.Only vine mealybug lays eggs onleaves and they may be found abovethe fruit zone. Starting in aboutNovember, population densitiesdecline and nymphs migrate to thelower trunk.

Timing of control measuresIt is very important to time insecti-

cide applications to coincide withperiods of maximum vulnerability ofeach pest. Due to the different lifecycle for the three species, controltiming differs. For information onwhich chemicals to use, please con-sult the University of CaliforniaGrape Pest Management Guidelinesat http://www.ipm. are two guidelines that addressmealybugs. The titles of the twoguidelines are 1) Mealybugs(Pseudococcus) for grape and obscureand 2) Vine mealybug.

GRAPE MEALYBUG: This pest is bestcontrolled at the crawler stage. Asdescribed previously, grape mealy-bug is seldom a pest; control isneeded only when populations arehigh and a high percent of the fruittouching the old wood is infested.Grape mealybug prefers vigorousvines. Keep records of infested fruitnear harvest and map the infestationat that time.

The most effective treatment is tocontrol crawlers from the overwinter-ing generation during delayed dor-mancy, just prior to bud break. In vine-yards with a history of infestation atharvest, monitor the spurs before budbreak. Gently peel the thin bark fromthe tip of the spur and look for theorange-to-yellow crawlers on one spurper vine in at least 30 vines. If 20% ofthe spurs are infested, a treatment maybe warranted.

In May, monitor the beginning of thesummer generation by examining thebase of spurs for mature females and forant movement on the vine. A treatmentmay be needed if more than 20% of thespurs are infested in late spring.

A post-harvest application shouldnever be used to control grape mealy-

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Growers work together in vine mealybug workgroupBY Nick Frey, Executive Director

Sonoma County Grape GrowersAssociation

When vine mealybug (VMB)was first discovered in theCarneros region, the grow-

ers and wineries organized a work-group led by Katey Taylor (viticultur-ist for Domaine Chandon). Theworkgroup provided trap placementand reading services for growers.The program expanded in 2005 toinclude growers outside of Carneros.Clearly, these growers recognize thevalue of working together to combatthis exotic pest.

Carneros growers were able tomanage VMB infestations in 2005and harvest fruit that met qualityexpectations. This was achieved withthe use of insecticides. Several newinfestations were found by vineyardworkers when leafing or cluster thin-ning. In addition to field workers,the group suggested that fruit sam-plers also be trained to identify VMB.When they remove berries or clus-ters, mealybugs inside the clustersare revealed.

It is also clear that VMB is spread-ing naturally now. No longer areinfestations only associated withnew vine plantings. If you have avineyard near an infested vineyard,you are at higher risk of becominginfested with VMB. However, newinfestations are not necessarily alongthe edge of the infested site.

Both Katey Taylor and LuciaVarela (University of CaliforniaCooperative Extension [UCCE]),emphasize the importance of grow-ers working together to slow thespread of VMB. If you are interestedin joining the VMB Workgroup in2006, contact Katey Taylor ([email protected])[email protected]. Participation

is not limited to growers in theCarneros area.

The 2005 VMB workgroup pro-gram had 339 trap sites. Of those, 90sites had VMB males. They do not, asyet, know the number of femaleinfestations associated with the 90sites that trapped males. As learnedpreviously, trappings in September/October detected the largest numberof VMB males, nevertheless earlytrapping is still worthwhile becauseearly detection is critical to reducefruit damage and loss and to haveany chance of eradicating an earlystage infestation.

Trapping should continue after aninfestation is found to track the effec-tiveness of insecticide treatments inreducing VMB numbers. The con-sensus of the group is that everyoneneeds to trap for VMB and everyoneneeds to talk to their neighbors tolearn if or where VMB exists relativeto their property.

The 2005 VMB workgroup resultssuggest that trap densities of greaterthan one per 30 acres may be needed.In windy locations such as Carneros,traps may be close to infested plantsand yet not catch any males. To besuccessful, traps need to be placeddownwind of the infestation whichmay be a challenge in a windy regionsuch as Carneros. It is also suggestedthat more traps be added to the trap-ping grid during September andOctober when male numbers arehighest.

If growers fail to identify or treat aVMB infestation, fruit quality will beaffected and ultimately vine healthwill decline. Experience to date indi-cates VMB monitoring, pesticidetreatment and sanitation can cost as

much as $1,000/acre under certaincircumstances if the grower’s objec-tive is eradication.

It is clear that new sustainablecontrols for VMB are needed.Potential new strategies include reg-istration of a new systemic insecti-cide with greater efficacy thanAdmire, especially on heavy soils,new ant-bait stations to reduce antpopulations (likely available in2007), mating disruption and newbiological control agents now beingevaluated.

Among the biological controlagents, it is hoped that parasites canbe released that will attack differentVMB life stages. Two species of para-sites under evaluation by KentDaane (UC Cooperative ExtensionSpecialist) are very aggressive in labo-ratory tests.

There is a growing consensus thatVMB is here to stay. Thus, we mustmake efforts to limit or slow itsspread. Trapping and talking withneighbors are critical actions everygrower should take. We also need todevelop cost-effective IPM programsthat rely less on heavy insecticideuse. There are promising options, butmore work is needed to create a suc-cessful IPM strategy.

The Sonoma County GrapeGrowers Association encourages theformation of additional VMB work-groups. Cooperation among growersis critical. Winery support is impor-tant, including training berry sam-plers to identify VMB. UCCE northcoast staff will continue to providetraining for vineyard employees andberry samplers in 2006. �

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bug. Depending on the harvest date, atthis time the majority of the populationis in the egg stage inside the ovisacunder the bark. No chemical kills theeggs, thus applying a treatment at thistime will disrupt natural enemies andnot control this pest.

OBSCURE MEALYBUG: The most effec-tive treatment timing for this species isalso the delayed dormant period;spurs can be monitored with a protocolsimilar to that listed above for grapemealybug. If additional treatments arerequired, systemic insecticides appliedwith irrigation water can be very effec-tive in late spring, more so in vine-yards with light soils.

If spring or summer foliar treat-ments are necessary, attempts shouldbe made to minimize adverse effects onthe resident population of beneficialinsects commonly present in vineyards.This can be achieved by leaving areas ofthe vineyard untreated, and by utilizinginsect growth regulators that primarilytarget mealybug pests.

VINE MEALYBUG: If vine mealybug isfound in a vineyard, treatment is recom-mended. The objectives for chemical

control are to obtain clean fruit and toavoid development of populations in thecanopy. Large populations in the canopymay hasten spread during leaf fall(which may occur prematurely due tovine mealybug feeding). Reducing thenumbers of vine mealybug in the canopyprior to harvest is essential to preventspread of the pest during harvest.

At the delayed dormant period, justprior to bud break, the majority of thepopulation is under the bark in the lowerpart of the trunk. Effectiveness of a treat-ment at this time may be improved ifbark is removed on the most infestedvines prior to the application. In areaswith light-textured soils, an effectivespring and early summer control is asoil-applied systemic insecticide atbloom as a single or a split application.

Summer foliar applications are war-ranted to insure clean fruit and to avoidhaving a large population in the canopy atharvest. When making summer applica-tions you may be limited by pre-harvestintervals. The earlier you find an infesta-tion the more chemical control optionsyou have to control this insect before har-vest. It is strongly recommended that all

vineyards be monitored with vine mealy-bug pheromone traps for early detection.For information on trapping, please con-sult the references cited below.

The most effective timing to reducevine mealybug populations is immedi-ately after harvest before the nymphsbegin to move to lower parts of thetrunk. This is when the highest percent-age of the population is exposed in thecanopy and on outside of the bark. Goodcontrol at post harvest will minimize theoverwintering population and mayreduce the need for a delayed dormantspray, when control is less effective. �

References Daane, K., E. Weber and W. Bentley.

“Formidable Pest Spreading ThroughCalifornia Vineyards.” Practical Winery &Vineyard, May/June 2004.

Smith, R. J. and L. G. Varela. Using VineMealybug Traps in the North Coast. CAPCAAdviser. January/February 2005.

UC IPM Pest Management Guidelines:Grape. University of California Division ofAgriculture and Natural Resources. Publ.3448.

Reprinted from:

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