Section 2 Virus Diseases of

Vegetable Plants

1. Virus Diseases of Tomato

Several virus diseases of tomato are not as pr

evalent as the wilt and foliar diseases. Three of

the more common virus diseases are tomato m

osaic (also referred to as tobacco mosaic), cucu

mber mosaic, and tomato spotted wilt. The to

mato mosaic virus can attack a wide range of p

lants, including tomato, pepper, eggplant （茄

子） , tobacco, spinach （菠菜） , petunia （矮牵牛

花） , and marigold （金盏草） .

1.1 Sympotom

On tomato, virus infection causes light and dark green m

ottled areas on the leaves. The dark green areas tend to be

somewhat thicker than the lighter portions of the leaf. The

leaf mottling is seen more easily if the affected plant surfac

e is partially shaded. Stunting of young plants is common,

and often is accompanied by a distortion and fern-like app

earance of the leaves. Older leaves curl downward and ma

y be slightly distorted. Certain strains of the virus can caus

e a mottling, streaking, and necrosis of the fruits. Infected

plants are not killed, but they produce poor quality fruit a

nd low yields.

The cucumber mosaic virus has one of the broadest

host ranges of any of the viruses. The disease affects a

number of important vegetables and ornamentals

including tomato, pepper, cucumber, melons, squash,

spinach, celery, beets, and petunia. Tomatoes infected

with the cucumber mosaic virus develop a slight

yellowing and mottling of the older leaves. Expanding

leaves typically become twisted, curl downward, and

develop a 'shoestring' appearance as a result of a

restriction of the leaf surface to a narrow band

around the midrib of the leaf. Diseased plants are

stunted and produce small quantities of fruit.

The tomato spotted wilt virus also has a

wide host range and can affect a number of

ornamental plants as well as tomato. Early

symptoms of spotted wilt on tomato are

difficult to diagnose. Young, infected plants

may show an inward cupping of leaves, and

the foliage may appear off-color or have a

slight bronze cast. In some cases, leaves

with exhibit dark purple flecks or small

necrotic concentric rings.

Fruit symptoms of tomato mosaic virus

Leaf symptoms of tomato mosaic virus.

Purple flecking of young leaves caused by tomato spotted wilt.

Fruit symptoms of tomato spotted wilt

As the disease progresses, plants may develop

dark brown to black streaks on the main stem.

Occasionally the top portion of the plant wilts.

The most characteristic symptom of spotted wilt

appears on the fruit. On young fruit, white to

yellow concentric rings, one-half inch in diameter,

develop on the fruit skin.  a bumpy or warty

appearance. The bright yellow rings on red, mature

fruit are quite striking and are easily diagnosed as

spotted wilt. The area within the ring typically is

raised, which gives the fruit.

1.2 Causes

Tomato mosaic, cucumber mosaic, and spotted

wilt are incited by viruses. The tomato mosaic virus

is very stable and can persist in dry contaminated

soil, in infected tomato debris, on or in the seed

coat. The virus is transmitted readily from plant to

plant by mechanical means. This may simply involve

picking up the virus while working with infected

plant material, then inoculating healthy plants by

rubbing or brushing against them with contaminated

tools, clothing, or hands. Aphids are not vectors of

the tomato mosaic virus, although certain chewing

insects may transmit the pathogen.

The cucumber mosaic virus overwinters in p

erennial weeds and may be transmitted to hea

lthy plants by aphid vectors (although tomato

es are not the preferred host of aphids) or by

mechanical means.

The cucumber mosaic virus cannot withstan

d drying, or persist in the soil. It also is more

difficult than tobacco mosaic to transmit mec

hanically. Thus, cucumber mosaic tends to pr

ogress more slowly than tobacco mosaic in a

field or garden.

The spotted wilt virus is transmitted from pl

ant to plant by several species of small insect

s called thrips. Thrips are less than one-quart

er inch in length, light green to brown, and ar

e extremely difficult to find on the plants. Sev

eral weedy hosts and ornamental plants may

serve as alternate hosts for the virus.

1.3 ControlVirus diseases cannot be controlled once the plant is infec

ted. Therefore, every effort should be made to prevent introd

uction of virus diseases into the garden. Many varieties of to

mato are available with resistance to tomato mosaic virus. S

anitation is the primary means of controlling the other two vi

rus diseases. Infected plants should be removed immediatel

y to prevent spread of the pathogens. Perennial weeds, whic

h may serve as alternate hosts, should be controlled in and

adjacent to the garden. Avoid planting tomatoes next to cuc

urbits, spinach, or other vegetables and flowers susceptible

to these diseases. Control of insects, especially aphids and t

hrips, will help reduce the likelihood of cucumber mosaic an

d spotted wilt.

1.4.1Tobacco mosaic virus (TMV) is distributed worldwide and may cause significant losses in the field and greenhouse. TMV is one of the most stable viruses known, able to survive in dried plant debris as long as 100 years. Many strains of TMV have been reported and characterized. TMV can be seedborne in tomato, is readily transmitted mechanically by human activities, and may be present in tobacco products. The virus is not spread by insects commonly occurring in the greenhouse or field.

1.4 Major Tomato Viruses

The symptoms in tomato vary greatly in intensity de

pending on the variety, virus strain, time of infection, l

ight intensity, and temperature. High temperatures, fo

r example, may mask foliar symptoms. The most char

acteristic symptom of the disease on leaves is a light-

and dark-green mosaic pattern (fig. 1). Some strains (r

eferred to as the acuba strains) may cause a striking y

ellow mosaic, whereas other strains may cause leaf m

alformation and “fernleafing“( 蕨叶 ). With the use of T

MV resistant or -tolerant varieties, plants may be infec

ted by some strains whose symptoms are latent. Ordi

narily the fruit from infected plants do not show mosai

c symptoms, but may be reduced in size and number.

Seeds suspected of carrying TMV should be t

reated with a solution of trisodium phosphate

(Na3PO4) for 15 minutes, rinsed in running tap w

ater, dried, and treated with a seed fungicide. C

ontrol of TMV spread in the greenhouse is espe

cially difficult because plants are handled more

often than in the field. Hygienic measures must

be taken to prevent the introduction and spread

of this virus. Choose only varieties resistant to

TMV and remove any suspicious plants as soon

as they are observed.

Single and double virus streak and tomato leaf rolling are thre

e separate diseases, which involve strains of TMV, mixed infecti

ons of TMV with other viruses, or interaction of TMV with a spec

ific tomato gene. Single virus streak is caused by a strain of TM

V that causes the same foliar symptoms as other TMV strains, b

ut under certain environmental conditions the plant develops br

own streaks （褐条病） on the stems and petioles( 叶柄） . On t

he fruit the symptoms appear as slightly sunken brown rings (fi

g. 2) Double virus streak is the result of a mixed infection of TM

V with potato virus X (PVX). Both viruses are readily transmitted

mechanically and, when they occur together, result in brown str

eaks along the petioles and stems, and small, irregular brown ar

eas on fruits. Leaf rolling is the result of TMV infection interactin

g with the wilt gene (wt) found in some tomato varieties.

1.4.2Cucumber mosaic virus (CMV) is the second most important virus disease of tomato. CMV has an extensive host range and is transmitted by aphids in a nonpersistent manner. Unlike TMV, CMV is not seedborne in tomato and does not persist in plant debris in the soil or on workers’ hands. CMV has been found in greenhouse plantings. Seedlings grown outdoors and left unprotected by isolation before moving indoors are one likely source of infection. Other sources of inoculum are the spread of CMV by aphids from infected plants in adjoining （邻近的） greenhouses (weeds under benches, ornamentals, or other vegetables) and by viruliferous （带病毒的）aphids entering through non-insect-proof vent windows.

The symptoms of CMV on tomato can be spectacular, with the most characteristic symptom being shoestringlike leaf blades (fig. 3) The symptoms of CMV can be transitory, and bottom leaves or newly developed top leaves may show a mottle similar to that caused by TMV (fig. 4). Because of the wide host range for CMV, sources of inoculum for field plantings are numerous. Avoid planting near weedy border areas or isolate tomatoes from such areas by growing taller, nonsusceptible barrier crops such as corn. No CMV-resistant or -tolerant varieties are currently available.

1.5.1Tobacco etch virus (TEV) and potato virus Y (PVY), are two common tomato viruses in some areas. The symptoms of TEV and PVY can be confused with TMV. Because some varieties carry partial resistance to TMV and none have been bred for resistance to either TEV or PVY, plants with a general mosaic suggest TEV or PVY infection. TEV symptoms are usually more severe (fig. 5), causing foliage distortion and severely stunted plants. Because of the lack of virus resistance and because both viruses are transmitted by aphids in a nonpersistent manner, most control measures are developed around the removal of solanaceous weed reservoirs. In southern states where tomato viruses are particularly troublesome, commercial growers have successfully used mineral oil sprays to delay virus spread in their crops.

1.5 Minor Tomato Viruses

1.5.2Potato leafroll virus (PLRV) is more commonly as

sociated with potato, but a tomato-specialized isolate

of PLRV has been identified. Leaf rolling and marginal

leaf chlorosis are the typical foliar symptoms seen wit

h this virus (fig. 6). Because this virus is transmitted b

y aphids in a persistent manner, aphid control should

reduce the amount of virus spread.

1.5.3Tomato spotted wilt virus (TSWV) can cause a sev

ere disease of tomato, especially in tropical areas whe

re thrips are plentiful. In addition to causing foliar necr

osis and brown streak of the stems and petioles, fruit

are severely mottled, making them unmarketable (fig.

7). Use of insecticides to control the vector reduces di

sease incidence.

1.5.4 Tomato big-bud mycoplasma (TBB) is a di

sorder of tomato more closely identified with su

btropical areas of the world where this disease

with the leafhopper as vector is more commonly

found. As the name implies, the bud’s size is gr

eatly accentuated by this mycoplasma-like orga

nism (fig. 8). Leafhoppers are generally not diffi

cult to control in temperate climates; thus, vect

or control should reduce the incidence of this di

sease.

2. Virus Diseases of Cucurbits

Many viruses affect cucurbits and cause mosaic

diseases. The most important of these viruses are c

ucumber mosaic virus (CMV), squash mosaic virus

(SqMV ，南瓜花叶病毒 ), watermelon mosaic virus

(WMV ，西瓜花叶病毒 ), zucchini yellow mosaic virus

(ZYMV ，小胡瓜黄花叶病毒 ), and papaya ring spot vi

rus (PRSV ，番木瓜环斑病毒 ). The viruses differ in t

he range of host plants they infect.

  The symptoms caused by different cucurbit virus

es are commonly very similar. It is impossible to ide

ntify these viruses with certainty based on symptom

s alone. Usually special laboratory tests are require

d to correctly identify a cucurbit virus.

zucchini yellow mosaic virus (ZYMV ，小胡瓜黄花叶病毒 )

Leaves of virus-infected plants often appear

mottled and distorted. Pumpkin plants infecte

d early in their development (near or before th

e time of flowering) are severely affected and

produce few fruit, and most of the pumpkins t

hat are produced are likely to be misshapen

（畸形的） or off-color. However, plants infect

ed after fruit reach full size may not show any

effect on yield or quality. Late-season pumpki

ns are especially prone to losses associated

with virus disease.

watermelon mosaic virus (WMV ，西瓜花叶病毒 ),

squash mosaic virus (SqMV ，南瓜花叶病毒 ) ，

papaya ring spot virus (PRSV ，番木瓜环斑病毒 )

Viruses survive in infected weed hosts. SqMV is seed-bo

rne. These pathogens are spread by insect vectors (especi

ally aphids) and mechanical operations that disturb plants

and bruise leaves and vines.

  Virus diseases of cucurbits can be controlled by plantin

g resistant varieties (wherever available), using virus-free s

eed, cultural practices, and insect control. Early planted fiel

d tend to have less damage than those that are planted late

r. Weed control within and around field is important. Avoidi

ng mechanical transmission of viruses is important. Insect

control for reducing incidence of virus diseases is effective.

However, Attempts to control insects for virus disease con

trol may be futile, because insects may transmit the virus b

efore insecticides are effective.

2.1 Mosaic Virus of Cucurbits

Mosaic virus is caused by the cucumber mosaic virus. This

virus is one of the most widespread and destructive pathogen

s on cucumbers, muskmelons( 香瓜） , and squash （南瓜） .

The virus is found worldwide and infects many different types

of plants including various vegetables, flowers, and weeds. M

uch of the early infection on cucurbits comes from floral crop

s which harbor the virus. Ornamentals as asters （紫苑） , chr

ysanthemums （菊花） , geraniums （天竺葵） , gladiola （剑兰） , larkspur （翠雀） , marigolds （万寿菊） , petunias （矮牵牛花） , phlox （夹竹桃） , zinnias （鱼尾菊） . Weeds may a

lso harbor the virus; examples include wild ground cherries

（野生酸浆草） , milkweed （马利筋） , pokeweed （美洲商陆） ,

and spurge （大戟） .

Plants can be infected at any stage of growth. When seedlin

gs become infected they remain small, turn yellow, and die. S

ymptoms on older plants include dwarfing of plants, mottling,

distortion, and downward curling leaves. Infected cucumber

fruit reveals patterns of white blotches interspersed with dar

k green spots that are raised into conspicuous blisters. Infect

ed fruit has a bitter taste （苦味） when eaten or becomes so

ggy （黏湿的） when pickled （腌制） . The fruit of infected s

ummer squash plants is knobby （多节的） and distorted. M

uskmelon and winter squash fruit rarely shows symptoms bu

t usually is off-color and bitter-tasting. Watermelons infected

with the virus usually show less stunting and mottling than c

ucumbers and muskmelons.

2.1.1 Symptoms

The virus survives the winter in roots of

susceptible plants, in greenhouses, and

possibly in seeds of wild cucumbers. Aphids are

the principle means of dissemination of the

virus. Mosaic also can be transmitted by the

cucumber beetle and by workers picking

cucumbers. As aphids feed on virus-infected

hosts, they become contaminated with the virus

and subsequently spread it to healthy plants.

2.1.2 Disease Cycle

Weed control around and within the planting is

important, since the virus can survive in many

weed plants. Most effective method of control

of common mosaic on cucumber is planting re

sistant varieties. These types of cucumbers ar

e resistant: Marketmore 70, Marketmore, Gemi

ni F1, Sweet Slice, and Victory. Cucumber pick

ing types that are resistant include Pioneer, Sp

artan, Valor, and Sulty.

2.1.3 Control

3. Virus Diseases of Leafy Vegetables and Celery

Lettuce, endive (escarole ，苣荬菜 ), spinach

（菠菜） , and celery （芹菜） are members of

different plant families, but share many of th

e same viral problems. most of these crops a

re produced on organic soils, but they may al

so be grown on mineral soils. Because these

crops are often planted near one another, the

viruses or other agents infecting the crops ar

e the same, and they are transmitted by the s

ame insect vectors.

The viruses infecting lettuce （莴苣 / 生菜） or endi

ve( 苣荬菜） include lettuce mosaic virus (LMV) ， cu

cumber mosaic virus (CMV), turnip （芜菁） mosaic v

irus (TuMV), broadbean wilt virus (BBWV ，蚕豆萎蔫病毒 ), Bidens mottle virus (BiMV ，鬼针草斑驳病毒 ), a

nd beet western yellows virus (BWYV ，西部甜菜黄疸病毒 ). Additional organisms infecting lettuce are lettu

ce big vein agent (LBVA) and aster （紫苑） yellows

mycoplasma (AY).

The two most important virus diseases of celery are

CMV and celery mosaic virus (CeMV); the occurrence

of aster （紫苑 ） yellows mycoplasma (AY) depends

upon the prevalence of the leafhopper vector.

3.1 Lettuce and Endive Diseases

Lettuce mosaic virus (LMV) can infect all le

ttuce types (crisphead, cos, Boston, bibb, an

d leaf) as well as escarole and endive. LMV i

s seedborne in all lettuce types, but not in e

ndive; and infected seed probably serves as

the chief source of inoculum, although weed

hosts are also recognized.

Plants infected through seed are referred to as seedb

orne "mother" plants because they can serve as virus

reservoirs from which aphids can spread the virus to

surrounding healthy plants. The mother plants show

early mosaic symptoms, are stunted, and never devel

op marketable heads. Secondary infected plants sho

w mosaic, leaf puckering, and deep or accentuated se

rration of the leaf margins in most lettuce types (fig.

1). Endive heads may be stunted, but generally show

only mild mosaic symptoms.

Two methods for controlling LMV are currently in use.

First, because of the prevalence of seedborne virus, l

ettuce seed is tested by three methods (direct readin

g of lettuce seedlings, inoculation of ground-up seed

with a sensitive indexing host, or, more recently, a se

rological technique) to ensure that each lettuce seed l

ot contains no infected seeds in a sample of 30,000 s

eeds (MTO or mosaic tolerance 7ero). A more succes

sful control measure is the incorporation of virus resi

stance into the principal lettuce types grown on both

mineral and organic soils.

3.1.1Cucumber mosaic virus (CMV) is the most imp

ortant virus disease of lettuce and the most difficul

t to control. Because the virus can infect more than

775 plant species, including many weed species (c

hickweed[ 繁缕 ], milkweed[ 马利筋 ], purslane[ 马齿苋 ],

dayflower[ 鸭跖草 ], etc.), many reservoirs （蓄水池） e

xist to overwinter the virus near growers‘ fields. Wi

nged aphids （有翅蚜） transmit the virus from bord

ering weedy areas to the crop to create primary inf

ection sites.

Secondary infections account for most virus spr

ead and occur when migrant aphids spread the vir

us from infected primary lettuce plants to surround

ing healthy plants. When large migrant-aphid flight

s occur. an entire field may become almost totally i

nfected in a matter of weeks.

Although the symptoms of CMV bear some rese

mblance to those of LMV, the mosaic is more inten

se with veinal chlorosis and, frequently, veinal bro

wning and necrosis when temperatures in the mid-

50s or lower occur (fig 2) .

Because weed hosts harboring CMV are common, a

concerted effort must be made by adjoining lettuce g

rowers to make weed sanitation and other programs

effective. Weed control must be done before or soon

after the crop is planted. Because migrant aphids ac

count for much of the virus spread and, normally, do

not colonize lettuce, insecticidal sprays are only mini

mally effective in reducing spread. Reducing primary

inoculum in the crop is so critical in delaying virus e

pidemics that major emphasis should be applied at t

his point. Make earliest plantings downwind from we

edy border areas, so that older lettuce plantings do n

ot serve as reservoirs of virus for subsequently plant

ed crops.

Although not extensively tested on lettuce, mineral

oil sprays are known to significantly reduce second

ary virus spread in many nonpersistent, aphid-trans

mitted virus diseases such as CMV, provided the tr

eatment is begun before primary inoculum exceeds

8-10%, and heavy virus pressure is not present in a

djoining fields. Spraying border areas with mineral

oils is also beneficial. The technique used is sophis

ticated; consult extension personnel for complete d

etails.

3.1.2Turnip mosaic virus (TuMV) is not a common disea

se of lettuce varieties, but escarole and endive are very

susceptible. Susceptibility to TuMV was inadvertently tr

ansferred to some lettuce varieties by breeding for resis

tance to downy mildew. TuMV typically causes veinal ch

lorosis and necrosis of lower leaves of both lettuce (fig.

3) and endive, severely stunting the plants and making t

he heads unmarketable.

Cruciferous weed hosts (shepherdspurse, etc.) are the p

rincipal source of inoculum for this aphid-transmitted vi

rus, and controls discussed under CMV are applicable.

3.1.3Broadbean wilt virus (BBWV), like CMV, can cau

se a serious disease of lettuce in susceptible varietie

s, resulting in large patches of infected plants (fig. 4).

Symptoms are similar to those of LMV and CMV, but

with low field temperatures the infected plants devel

op severe veinal necrosis. Some varieties are very su

sceptible whereas others display good tolerance to i

nfection.

BBWV is transmitted by aphids in a nonpersistent m

anner. The major weed hosts in New York have been

identified as broadleaf plantain (Plantago ma/or) and

buckhorn plantain (P. Ianceolata).

3.1.4 Bidens mottle virus (BiMV) has been recovere

d from lettuce and endive in Orange County, but is

not widely distributed in the state. Symptoms caus

ed by BiMV are similar to those of LMV in both lett

uce and endive. The lettuce variety Valmaine (a ro

maine or cos type) is naturally resistant to BiMV an

d has been used in breeding programs for joint res

istance to BiMV and LMV.

BiMV is not seedborne in either lettuce or endive, a

nd principal weed hosts for this aphid-transmitted

virus are beggarticks, pepperweed, and others.

3.1.5 Beet western yellows virus (BWYV) is an important

virus disease of lettuce and endive in California, Arizona,

and Florida. Although not formally recognized in this stat

e, weed hosts such as shepherdspurse are present. BWY

V causes a pronounced chlorosis of the outer leaves of le

ttuce (fig. 5) and escarole.

Although spread by many of the same aphid species that

are vectors for the other common lettuce viruses, BWYV i

s transmitted in a persistent manner, meaning that a long

er time is required to acquire and then transmit the virus.

Insecticidal sprays would presumably help to delay the s

pread of this particular virus disease.

3.1.6 Lettuce big vein agent (LBVA) is probably caused

by a virus, although the virus particle has not been see

n with the electron microscope. This disease differs gr

eatly from the other lettuce virus diseases; its vector in

nature is a soilborne fungus (Olpidium brassicae). The

virus is acquired by the fungus protoplast in virus-infe

cted roots and is carried by fungal zoospores, which in

fect healthy roots and release the virus.

Infected lettuce plants are striking, with leaves showin

g enlarged and lightened veins and petioles (fig. 6). Lea

ves are also thickened and distorted, and heads are sm

aller than normal.

Because of the soilborne nature of the disease, no prac

tical control measures are available.

3.1.7Aster yellows mycoplasma (AY), formerl

y thought to be caused by a virus, can infect

a wide range of plants in addition to lettuce a

nd celery. The disease results in strikingly ye

llowed and stunted plants (fig. 7), which are

unmarketable. This disease may occur annua

lly, its extent being determined by the prepon

derance of the aster leafhopper vector (Macr

osteles J:ascifrons). Controls are based upo

n the use of insecticidal sprays to reduce the

only known vector.

3.2 Virus Diseases of Spinach

Cucumber mosaic virus (CMV) infection of

spinach has long been called "spinach blight" by

growers, but should not be confused with fungal

diseases for which the term blight is more

commonly used. The disease is caused by CMV,

which is covered in detail in other sections of

this fact sheet. Infected spinach plants may

show a variety of symptoms including stunting,

yellowing, and mottling of the older leaves and

malformation of the younger leaves.

Good resistance to CMV is available, but this

resistance is temperature dependent; at

temperatures above 80° F crown necrosis will

develop (fig. 8), which is similar to infection

with broad bean wilt virus (BBWV) without the

need for high temperatures (fig. 9). With the

exception of the high temperature response

for CMV infection, resistance for CMV in

spinach has provided an effective control

measure for over 60 years.

3.2.1Broadbean wilt virus (BBWV) has previously been

mentioned in this report. This virus does cause a major

disease of spinach, particularly in the autumn crop whe

n aphid vectors are most plentiful and much inoculum i

s present from earlier plantings.

Symptoms of BBWV closely resemble those caused by

CMV, and therefore, identification is impossible under fi

eld conditions (fig. 9).

Control involves the removal of the principal weed host

s P. major and P. lanceolata. Mineral oil sprays to delay

virus spread have been used only on a trial basis and h

ave not been tested under heavy disease pressure.

3.2.2Lettuce mosaic and turnip mosaic viruses (LMV a

nd TuMV), in addition to infecting lettuce, can also infe

ct spinach. Neither LMV nor TuMV is seedborne in spi

nach, but an adjoining lettuce crop could inadvertently

lead to infection of spinach. LMV symptoms on spinac

h consist of bright yellow circular spots that coalesce i

nto a diffuse dull chlorotic mottle. Young infected leav

es are small, mottled, and distorted. Older plants are s

tunted, and old infected leaves die prematurely. TuMV-

infected plants show diffuse mottle, leaf distortion, an

d stunting. Lower leaves become necrotic and abscise

prematurely.

3.3. Celery Diseases

Cucumber mosaic virus (CMV), also called southern ce

lery mosaic, is the principal virus disease of celery in Ne

w York. The chief characteristics of this virus disease an

d control measures have already been discussed.

CMV symptoms consist of general mosaic, which, on o

lder leaves infected earlier, develops into chlorotic yello

wing and veinal necrosis (fig. 10). Plants infected when y

oung will also be stunted. The petioles on similarly infec

ted plants may also show slightly sunken, buffcolored le

sions (fig. 11). If plants are infected at an early age, inner

petioles are also affected, making the plant unmarketabl

e.

3.3.1 Celery mosaic virus (CeMV), also called western celery mos

aic because it was first identified in California, can also be a seri

ous disease of celery. The virus is transmitted by several aphid s

pecies in a nonpersistent manner and is limited only to umbellife

rous plants (celery, carrot, parsley, etc.). Plants infected at an ea

rly age are greatly stunted, and the foliage, after showing early m

osaic, becomes cupped and malformed (fig. 12). Because of the l

imited host range, destruction of umbelliferous weeds is the rec

ommended control measure.

3.3.2 Aster yellows mycoplasma (AY) may also infect celery on a

n annual basis. This disease is described under "Lettuce and En

dive Diseases."