Diagnose & Treat
Plant Diseases

Symptoms of alfalfa mosaic include bright yellow mosaic or calico pattern on leaves. Older leaves develop a yellow mottle with enlarged veins. Infected plants may be stunted.

Alternaria leaf blight initial symptoms typically begin on older leaves as brown spots surrounded by a yellow margin. At later stages of disease development, dark brown to black irregularly shaped necroticlesionsdevelop on leaf blades and petioles. Leaves can be killed when foliar spots grow together or by lesions that develop on petioles. At advanced stages of disease development, leaves will have a scorched appearance. This disease weakens tops that then break during mechanical harvest leading

The twoAlternariaspecies,A. brassicaeandA. brassicicola,cause similar symptoms. Small, dark specks first develop on leaves and later enlarge into circular, tan spots (0.25-0.5 inch in diameter). The spots caused byA. brassicicolatend to be darker than those caused byA. brassicae.If conditions are favorable, dark green spores of the pathogen will grow on the spots. Such growth causes the spots to have concentric rings in them. Old leaf spots become papery in texture and may tear. When the dr

Symptoms of Alternaria stem canker appear on stems, leaves, and fruit. Dark brown to black cankers with concentric zonation occur on stems near the soil line or aboveground. Cankers enlarge, girdle the stem before harvest, and kill the plants. Vascular tissue about 2 inches above and below the cankers exhibit brown streaks. Dark brown to black areas ofdead tissuebetween leaf veins are caused by a toxin produced by the fungus. Dark brown sunken lesions with characteristicconcentric ringsdevelop o

Ammonium toxicity is most commonly seen on young lettuce plants that are between thinning and rosette stages. Aboveground symptoms of ammonium toxicity are similar to those caused by root injury: dull, dark green or gray-green leaves, temporary leaf wilting, desiccation, and yellow V-shaped sections. As the symptoms progress, leaf margins may turn brown, and the plant may become severely stunted or die.Typically, small root hairs and lateral roots are brown and dead, and a longitudinal cut down

Angular leaf spot occurs most commonly on cucumber, but is also found on melons in California. Lesions on the foliage begin as water-soaked spots that later turn gray or tan. Spots may initially develop a yellow halo. As the affected tissue dries, the internal tissue may fall out, giving the leaf a tattered appearance. The lesions are delimited by veins, giving them an angular shape.Fruit lesionsare usually superficial.

Sunken dark spots on fruit/pods

Copper spray/remove infected parts

Symptoms of aster yellows on lettuce include blanching and chlorosis of the young heart leaves. The center leaves fail to develop normally and remain as short, thickened stubs in the middle of the head. Outer leaves become yellow and twisted. Pink to tan latex deposits collect on the underside of midribs of affected leaves. If young plants are infected, outer leaves yellow and the plants may be severely stunted. If older plants are infected, latex spots in the interior of the head may be the onl

Bacterial blight infections start as small, angular-shaped, water-soaked specks on leaves that are often surrounded by yellow borders. As the disease develops, specks enlarge and coalesce together into larger, irregularly shaped gray-to-tan spots. Leaf spots are visible from both top and bottom sides of leaves. Symptoms may resemble those of the more familiar bacterial leaf spot disease.

There are usually no symptoms of bacterial canker on seedlings; however, on young plants symptoms consist of poor growth and temporary wilting of branches. Lower leaves yellow and shrivel, but symptoms may not show until flowering. On mature plants there are two kinds of symptoms. One kind is from systemic infections (i.e., the bacteria enter the vasculature and invade much of the plant) and the other resulting from secondary infections (i.e., the bacteria cause local infections of leaves, stem,

Although all cucurbits are susceptible, bacterial fruit blotch is only a problem on watermelon. Two- to three-week old fruit are most susceptible to infection. Fruit symptoms begin as small, water-soaked spots. These lesions expand rapidly and may cover the upper surface of the fruit. Later the lesions may turn red brown and develop cracks and a general fruit rot may follow. A white bacterial ooze may form in the lesion during wet weather.

Bacterial leaf blight is often first noticed in fields as brown areas about 3 to 4 feet in diameter. Leaf symptoms appear as irregular brown water-soaked spots surrounded by ayellow halo, often beginning on the leaf margins.Spots grow together and result in leaf death and dark brown streaks develop on leaf petioles. Floral parts may also be blighted. A sticky amber-colored bacterialexudate, which is a diagnostic sign of the disease, may be present on leaves or observed flowing downward on petiol

Initial symptoms of bacterial leaf spot consist of water-soaked, irregularly shaped spots that measure 0.12 to 0.25 inch in diameter. As the disease develops, these small spots enlarge to as much as 0.5 to 0.75 inch in diameter, are angular in shape, and turn dark brown in color. Occasionally, spots have black sections or edges, or they may have faint yellow halos. On leaves with numerous spots, the spots sometimes merge together, resulting in the death of large areas of the leaf. Spots are

Bacterial soft rot is recognized as a soft, watery, and slimy decay of the carrot root, not associated with any fungal growth and accompanied by a foul odor. The decay rapidly consumes the core of the carrot, often leaving the epidermis intact. Aboveground symptoms include a general yellowing, wilting, and collapse of the foliage. Soft rot can occur in the field and during storage.

Bacterial speck appears as dark brown toblack lesionsof various sizes and shapes on leaves, fruit, and stems. Tissue adjacent to the lesions is initially yellow. Leaf lesions are frequently concentrated near margins, causing extensive marginal necrosis (tissue death).Lesions on immature fruitare slightly raised and small, varying in size from tiny flecks to 0.125 inch (3 mm) in diameter and causeraised black spotson mature fruit. Fruit lesions are superficial, seldom penetrating more than a few

Bacterial spot develops on seedlings and mature plants. On seedlings, infections may cause severe defoliation. On older plants, infections occur primarily on older leaves and appear as water-soaked areas.Leaf spotsturn from yellow or light green to black ordark brown. Older spots are black, slightly raised, superficial and measure up to 0.3 inch (7.5 mm) in diameter. Larger leaf blotches may also occur, especially on the margins of leaves. Symptoms onimmature fruitare at first slightly sunken an

Sudden wilting of whole plant/bacterial ooze in stem

No cure - remove plants

Theinternodesof infected plants shorten, resulting in extremely stunted plants. The upper portion of infected plants resembles arosetteor small flower bouquet. Leaves turn yellow or light green and may roll upward. Fruit are small and remain upright instead of drooping. Plants infected at an early age may die.

On lettuce, symptoms of beet western yellows rarely develop until plants reach rosette stage. At this point in crop development, the older leaves begin to turn yellow. This yellowing continues until all the oldest, lower leaves are bright yellow, or (less frequently) almost white, with the main leaf veins remaining green. Yellowed leaves often have a thick, brittle texture. Yellowing can progress until the wrapper leaves adjacent to the head also turn yellow, and head color may be unacceptably l

Beet yellow stunt causes pronounced yellowing of older leaves; later, infected plants collapse prematurely and die. Internally, the phloem tissue of the stem and crown is brown and necrotic.

Big vein disease causes the veins in leaves to become very enlarged and clear. Such deformities are easily seen if the leaf is examined with the light source behind it. The enlarged veins cause the rest of the leaf to be ruffled andmalformed. Severely affected plants can be so deformed that they are unmarketable. Head lettuce varieties may even fail to form a head. However, infected plants showing less severe symptoms can still be harvested.

The most serious symptoms occur on stems near the soil line where elongated, sunken, brown lesions form. These lesions may girdle the stem, resulting instunting, wilting, and general poor growth of the plant. If the lesions enlarge, the stem may break, causing the plant to fall over. Lesions usually contain minute, spherical, dark structures that are thefruiting bodiesof the pathogen. If conditions are right, pink masses of spores exude from these structures. If seedlings are infected ear

Black mold is characterized by obvious lesions that appear on the surface of ripe fruit. Lesions are light to dark brown and vary from small flecks affecting only epidermal tissue to large, more or less circular, sunken lesions with decay extending into the carpel wall and often into the seed locule. During warm, humid weather the fungus may sporulate to form a black, velvetlike layer on the surface of the sunken lesions.

V-shaped yellow lesions/black veins

Copper spray/remove infected plants

Symptoms include a water-soaked, brownish-gray to brownish-orange, soft wet rot that occurs on the oldest leaves in contact with the soil. These old leaves are often damaged or senescent and are therefore particularly susceptible. From these leaves, the pathogen moves into the healthy parts of the lettuce plant and causes a decay of the crown. A characteristic fuzzy gray to brown growth covers diseased areas, especially basal leaf and crown tissue that is shaded and protected from drying by over

Fuzzy brown rot on fruit/mummified fruit

Remove mummies/copper spray

Carrot motley dwarf is caused by the combined infection of carrots by two virusesCarrot redleaf virusandCarrot mottle virus.Plants infected in the seedling stage will be severely stunted and yellow to red in color. Plants appear as if they are suffering a nutritional deficiency. Roots may also be stunted. When plants are infected at later stages of growth, symptoms are inconspicuous, plants may or may not have stunted growth, but some leaves will be red or yellow, or a combination of red and yel

Symptoms on plants infected withCarrot thin leaf viruscan vary. In general, leaflets appear thinner than normal, giving the plant an overall unusual appearance. Some leaves may have leaflets that are distorted and show a mosaic pattern. Leaflets of plants infected at a young stage may be extremely thin, hence the name of the virus. The virus has not been shown to cause yield losses in California.

Cavity spot is characterized by small, sunken, elliptical to irregularly shapedlesionson the surface of carrot taproots. Individual lesions are usually less than 0.5 inch (1.3 cm) in diameter, but can be much larger, especially on processing varieties. Infections occur anywhere along the taproot, but lesions tend to be more abundant on the upper third of the root. Lesions become dark and increase in size as carrot roots mature.

Orange spots on leaves/deformed fruit

Remove nearby cedars/fungicide spray

Cercospora blight can occur on any above ground carrot tissue. Symptoms appear as small, circular, tan to brown lesions, and curled leaf margins. The tan to brown lesions initially surrounded by a chlorotic halo often enlarge into brown necrotic spots. As the disease progresses, the leaflets become yellowed and curl at the margins. Lesions on leaf petioles, stems, and flower parts are usually elliptical and dark brown. Under heavy disease pressure, severe loss of foliage may occur eventually lea

Charcoal rot affects all cucurbits. First symptoms are yellowing and death of crown leaves and water-soaked lesions on the stem at the soil line. As the disease progresses, the stem of infected plants ooze amber-colored gum, and the stem eventually becomes dry and tan-to-brown in color. The stem may be girdled by the lesion, resulting in plant death. Numerous microsclerotia, visible as black specks, are embedded in the dead plant tissue.

Cladosporium leaf spot is characterized by round, tan leaf spots that rarely exceed 0.25 inch in diameter. Dark green spores and mycelium later develop in the centers of these spots. The presence of dark green sporulation distinguishes Cladosporium leaf spot from anthracnose and Stemphylium leaf spot diseases, both of which also form circular lesions.

Wilting/swollen distorted roots

Lime to raise pH/remove infected plants

Common rust causes pustules that may appear on any aboveground part of the corn plant but they are most abundant on leaves. The pustules, which may erupt and become powdery, occur nearly simultaneously on both leaf surfaces. They are golden brown to cinnamon brown, becoming black as the spores mature.

Common smut is easily recognized by the tumorlike galls that form on any aboveground plant part. The conspicuous galls that replace kernels are covered with a greenish-white papery tissue. As the galls mature, the interior darkens and turns into masses of powdery, dark olive-brown to black spores. Ear galls may reach several inches in diameter. Galls that form on other plant parts, including the tassels and leaves, are much smaller.

Early symptoms of corky root are yellow bands on taproots and lateral roots of lettuce seedlings. These yellow areas gradually expand, taking on a greenish-brown color and developing cracks andrough areason the surface of the root. As the disease severity increases, the entire taproot may become brown, severely cracked, and nonfunctional; thefeeder root systemwill also be reduced and damaged. At this point, roots are very brittle and easily break off when examined. Corky root may cause internal

Infected rootsof plants with corky root rot are distinctly corky. Extensive brown lesions, often arranged in bands with lengthwise cracking of the cortex, develop on the larger roots. The tips of infected older roots are pinched off. Small feeder roots may be completely decayed. Infected plants are stunted and slow-growing. Branches on mature plants may die back from the tips.

Corn stunt, as the name implies, results instunted plants. Severely infected plants and those infected early in their development may be only 5 feet tall with very short internodes, rather than the usual 10-12 feet in height. The stalk may have multiple ears, sometimes as many as 6-7 on a single plant. The ears are small and do not fill properly leaving a large number of blank spaces on the ear. The kernels that do develop are frequently "loose" leading to what is called "loose tooth e

Sclerotiniainfection may occur at any stage of growth, and extensive root decay will occur before symptoms of wilt and collapse appear on the above ground of the plant. Infection is always accompanied by a characteristic cottony, white mycelium that appears on the surface of the infected tissues, usually near the soil line. On or inside the white mycelium appear black, round to irregular-shaped structures (sclerotia), which are about 0.1 to 0.4 inch (0.3–1 cm) in length. Sclerotia are survival s

Symptoms on plants with cucumovirus mosaic diseases can vary, but in general, plants show an overall lighter color along with mosaic patterns (alternating light and dark green areas) on at least some leaves, especially on the younger leaves. Often, the main leaf vein is distorted and somewhat zigzag in appearance. Plants generally show stunting, leaf curling, and mosaic, and mature leaves can develop necrotic areas shaped like oak leaves.Fruitmay be malformed and have conspicuous concentric ring

Cucurbit aphid-borne yellows luteoviruscauses a generalyellowing of the older leaves, which become thick and leathery. The major veins of these leaves remain green. Growth and yield of infected plants may be reduced.

Infected cucurbit plants initially show achlorotic (yellow) spotting, which eventually develops into a strikinginterveinal chlorosis(yellowing) in which the veins remain more or less green but the rest of the leaf turns bright yellow. Leaves will often roll upward and become brittle. Fruit on infected plants may appear normal but often have reduced levels of sugars; this results in poor marketability and economic loss. Symptoms ofCucurbit yellow stunting disorder virusinfection can be

Plants with curly top arestuntedbecause growth ceases. Plants turn yellow to bronze with purple-tinged leaves. Plants become stiff and soon die.Green fruitturns red, regardless of age.

Seedlings collapse at soil line

Cinnamon/chamomile tea/better drainage

Yellow patches on top/gray fuzz underneath

Copper fungicide/remove infected leaves

Dark spots with rings (target pattern) on lower leaves

Copper spray/remove lower leaves/mulch

Exserohilum root rot causes brown lesions on primary roots and later on secondary roots of the first and second whorls. The affected roots become black and necrotic. Aboveground symptoms include wilting, stunting, and yellowing of leaves, but these symptoms are not always apparent.

Blackened shoots curved like shepherd's crook

Prune 12 inches below infection/sterilize tools

Some species of bacteria or other microorganisms either cause or are associated with a copiouswhite frothy materialthat exudes from the axil of leaf petioles and the main stem and maydrip to the soil. A wound may or may not be obvious. This condition usually occurs during warm weather and when ample soil moisture is present. Fruit covered with the sticky exudate may be unmarketable. If severe, affected branches stop producing.

Although all cucurbits are susceptible, Fusarium crown and foot rot is a problem only on squash and pumpkin. The fungus causes water-soaked lesions on thestemat the soil line. Infected plants wilt and die. On the fruit, the lesions usually begin on the area that is resting on the ground.Fruit lesionsare firm and dry, with the decayed area exhibiting a concentric ring pattern.

Foliar symptoms on plants with Fusarium crown and root rot include yellowing along the margin of the oldest leaves, followed by necrosis. Dry brown lesions develop in the cortex of the tap or main lateral roots. A necrotic lesion may also develop on the surface of the stem from the soil line to 4 to 12 inches above it. Internally, a reddish brown or chocolate brown discoloration extends no more than 6 to 12 inches above the soil line. Infected plants may be stunted and wilted, and older plants

Fusarium ear rot results in white to salmon-pink discoloration of individual kernels or groups of kernels scattered over the ear. A white to pinkish weft of mycelia covers the kernels, especially on the tip of the ear. In severe infections the ears may be completely consumed by the fungus, leaving lightweight husks cemented to the kernels by mycelia.

Fusarium foot rot causes varying degrees of interveinalchlorosis and necrotic spottingon young foliage. Foliar symptoms may be similar to certain viruses (tomato spotted wiltoralfalfa mosaic). Flowers are often necrotic. Aboveground symptoms may be restricted to single branches. In severe cases, plants die. Adark brown lesion, about 0.5 to 1 inch (1–2.5 cm) long, is visible on the tap root or a main lateral root. Often the lesion completely girdles the root. The lesion usually occurs on the root

Corn plants with Fusarium stalk rot exhibit rotting of the roots, plant base, and lower internodes. The rot normally begins soon after pollination and becomes more severe as the plant matures. The lower stem becomes soft and eventually collapses. The pith inside the stems becomes tan to pink and disintegrates, leaving the vascular strands intact.

Yellowing/wilting one side of plant

No cure - remove plants

In California, this pathogen affects primarily cabbage. Symptoms consist of yellowing of the lower leaves, often on one side of the plant. These leaves later turn brown and drop off. A brown discoloration of the water-conducting tissues (xylem) is characteristic of this disease. With time the entire plant may yellow, wilt, and collapse.

Gray mold appears on young plants as gray-brown velvety mold covering stems or leaves. Infections that girdle the stem cause wilting above the infected area. In the field gray spores cover dying flowers and thecalyx of fruit. Under a hand lens, the spore-bearing structures resemble bunches of grapes. Infections spread from flowers or fruit back toward thestem, which turns whiteand develops a canker that may girdle it.Green fruit decays and turns light brown or gray, starting at the point where i

Head smut is characterized by large smut galls that replaceearsor tassels. The galls are first covered by fragile, creamy white membranes that eventually rupture to release masses of dark brown spores. Within the masses of spores are more or less intact threadlike strands of vascular bundles, giving the spore masses a stringy appearance. The vascular bundles within the galls readily differentiate head smut from common smut. In head smut,leaflike proliferationsoften occur in tassels and pa

Symptoms on plants infected withImpatiens necrotic spot virusinclude overall yellowing (chlorosis), dead (necrotic) spots on leaves or terminal shoots, and general stunting. Fruits show chlorotic spots, red or green areas surrounded by yellow halos, and concentric rings that may become necrotic. Symptoms are similar to those caused by another tospovirus,Tomato spotted wilt virus(TSWV) (for more information on this virus, seeTOMATO SPOTTED WILT).

Leaf symptoms of late blight first appear as small,water-soaked areasthat rapidly enlarge to form purple-brown, oily-appearing blotches. On the lower side of leaves, rings of grayish white mycelium and spore-forming structures may appear around the blotches. Entire leaves die and infections quickly spread to petioles and young stems.Infected fruitturn brown but remain firm unless infected by secondary decay organisms; symptoms usually begin on the shoulders of the fruit because spores land on fr

Leaves of plants infected withlettuce chlorosis virusexhibit severe yellowing, rolling, brittleness, and vein-clearing. Plants infected early are stunted.

Romaine and leaf lettuce infected with this virus exhibit characteristic symptoms, although symptoms are likely to vary depending on the age of plants when infected, time of year, and cultivar. Plants can be severely stunted and mature, diseased plants may only reach 6 to 8 inches in height. The outermost leaves are extensively yellowed. The younger, inner leaves often remain dark green, but can be rough and leathery in texture. In some cases, the older leaves develop necrotic spotting that can

Two species ofSclerotiniainfect lettuce in California and cause the lettuce drop disease: in coastal growing areasSclerotinia minoris the primary species of importance, while in other areasS. sclerotiorumis more prevalent.Sclerotinia minoronly infects the stems and leaves in contact with the soil. Once infection takes place, the fungus will cause a brown, soft decay that eventuallydestroys the plant crown tissue. Older leaves then wilt and later the entire plant will wilt and collapse, making it

Symptoms of lettuce mosaic vary greatly. Leaves of plants that are infected at a young stage are stunted, deformed, and (in some varieties) show a mosaic or mottling pattern. Such plants rarely grow to full size; head lettuce varieties that are infected early fail to form heads.Plants that are infected later in the growth cycle will show a different set of symptoms. These plants may reach full size, but the older outer leaves will be yellow, twisted, and otherwise deformed. On head lettuce, the

Symptoms of maize dwarf mosaic include narrow, light green to yellow streaks along the veins of leaves, leaf sheaths, and husks. As infected plants continue to grow and the temperature rises, the mosaic symptoms may disappear while the young leaves become more yellow. Plants may be stunted and have numerous tillers and poor seed set. Infected plants may be predisposed to ear rot and stalk rot.

Small lesions (2 to 4 mm) occur onfruit, stems, and leaves. Initially the spots appearwater soakedbut soon the center dies and turns tan. Spots are superficial on fruit but may have a slight overgrowth causing bumpiness.

Symptoms on plants affected by mosaic diseases can vary. In general, plants develop an overall lighter coloring and a bushy appearance. Close up symptoms include a mosaic (alternating light and dark green areas) on some leaves, especially the younger ones. Leaves may also be curled. Fruit may bedistortedand develop mosaic symptoms. Internally, brown areas and necrotic areas develop and the fruit do not ripen normally.

Symptoms on plants infected with cucumoviruses can vary. Generally, plants appear lighter in color and are bushy and stunted. Close up symptoms include a mosaic (alternating light and dark green areas) on at least some leaves, especially on the younger leaves. Leaves may exhibit a shoestring-like appearance. Fruit production is greatly reduced. These symptoms can be confused with those caused bytobacco mosaic virus.

Puckered red/yellow distorted leaves

Copper spray (dormant only)

Early symptoms of Phoma basal rot on romaine lettuce consist of yellowing and wilting of lower leaves. Affected plants may later show an uneven appearance because one side of the foliage grew normally while the diseased side of the plant remained stunted and short. As plants mature, the entire plant becomes stunted and eventually wilts and collapses. The wilting and collapsing symptoms are somewhat similar to lettuce drop and Botrytis crown rot.Examination of affected plants reveals distinct,bla

Phytophthora fruit and crown rot is most commonly found onsquashand pumpkins, but all cucurbits are susceptible. This disease occurs suddenly in a field and plants wilt and die within a few days of infection.Infected fruitrot quickly. The roots and stems are soft, water-soaked, and brown. Adowny growthis often apparent on plant lesions during periods of high humidity.

The external surfaces and internal tissues of infected roots are water-soaked, dark in color, and rotted. Leaves (especially older ones) first turn purple-red, and later yellow, and thenwilt. The plant may be stunted, and with time the entire plant wilts. The stem near the soil line may turn black and become soft.

Beet Leafhopper-Transmitted Viresence AgentLeaves of infected plants are reddish purple with mildchlorosis. Infected plants often bolt prematurely. Flower parts are malformed; petals that would normally be white are green, and the flowers proliferate to form multiple, compound, leafy umbels. Diseased plants haveunmarketable rootsthat are thin, woody, and hairy.Aster Yellows PhytoplasmaLeaves ofinfected plantsare twisted, stunted, and yellow. Leaflets may be reduced to short scales. Flower parts

Symptoms on plants with potyvirus mosaic diseases can vary, but in general, plants show an overall lighter color along with mosaic patterns (alternating light and dark green areas) on at least some leaves, especially on the younger leaves. Plants will often show stunting, leaf curling, and fruit distortion along with the mosaic pattern on leaves. Symptoms may be similar to those caused by cucumber mosaic virus.

Each virus produces similar symptoms and mixed infections are common. The first symptom is a clearing of veins, followed by development ofmosaic patternsor mottling consisting of irregularly shaped, dark green areas alternating with light green or yellow areas. Leaves on some species and cultivars are drastically reduced in size and growth is often retarded.Watermelon mosaic virustends to cause raised, blisterlike areas on leaves and to reduce leaf size severely.Zucchini yellow mosaic vi

White powdery coating on leaves

Neem oil/baking soda spray/milk spray

Pythium stalk rot commonly becomes apparent when the plant suddenly falls over. Infection usually involves a single internode near the soil line. Diseased areas are dark brown, water-soaked, soft, and collapsed. The stalks may be twisted and distorted. Infected plants remain green and turgid for a short time after collapse because the vascular bundles remain intact.

Damping-offThis soil fungus, along withPythiumspecies andThielaviopsis basicola,can sometimes cause damping-off of lettuce. Seedlings may be killed before or just after emergence. Infected seedlings exhibit decayed roots and brown lesions on stems. When seedlings are infected, the stem tissue collapses and plants fall over and die.Bottom rotIn some regions, particularly the San Joaquin Valley and desert areas,R. solaniinfects lettuce plants as the heads begin to form.Brown, sunken lesionsform on

In California, this disease occurs primarily on Brussels sprouts. Symptoms consist of circularleaf spots(0.5 inch in diameter) that range in color from light brown to black. With time, these spots develop concentric rings, much like a target pattern. Small, sphericalfruiting structuresmay also be observed within the leaf spots. If disease is severe, some defoliation may take place. This pathogen may also infect the sprouts, causing dark lesions on outer leaves.

Root dieback of carrots produces excessively branched or stubbed roots. The fungus kills young taproots less than 2 weeks after seed germination, which reduces root length or stimulates multiple root formation (forking), or both.Pythiumspp. can also cause damping-off of carrots.

Aboveground symptoms of root rot include rapid wilting and death of affected eggplant plants. Close examination of the roots and stems of affected plants is necessary to confirm the cause of disease. The disease can develop at any stage of eggplant plant growth. Tap roots and smaller lateral roots show watersoaked, very dark brown discoloration of cortical and xylem tissue. Very few lateral roots remain on diseased plants and the taproots may also be shorter compared to those of healthy pl

Two species ofSclerotiniacause disease on cole crops.Sclerotinia minoronly infects stems or leaves in close contact with the soil. Once infection takes place, water-soaked, brown, necrotic areas develop on these structures. The necrotic areas rapidly turn into soft, watery rots. Plants then wilt and collapse. Profuse amounts of white mycelial growth and numerous small (up to 0.125 inch or 3 mm), black, hard resting bodies called sclerotia, form on the outside and inside of the stems.Sclero

Small dark spots with light centers on lower leaves

Copper spray/remove affected leaves

Southern blight is characterized by a soft watery decay of the taproot at or near the soil line. The disease develops rapidly, resulting in wilting and yellowing of the carrot top. White mats of mycelium develop on the carrot root and in the adjacent soil. Tan to brown roundsclerotia(resting structures) about the size of a mustard seed (1.5 mm) develop on mycelial mats. The abundant sclerotia are a good diagnostic feature of southern blight.

Symptoms of squash mosaic include mosaic patterns and mottling of theleafalong with deformed fruit.

Initial symptoms of Stemphylium leaf spot on leaves consist of small (0.13 to 0.25 inch diameter), circular to oval, gray‑green leaf spots. As the disease progresses, leaf spots enlarge, remain circular to oval in shape, and turn tan in color. Older spots coalesce, dry up, and become papery in texture. Visual signs of fungal growth are generally absent from the spots; hence this problem is readily differentiated from foliar diseases in which purple growth (downy mildew), green spores (Clad

Symptoms of sudden wilt begin when the crown leaves yellow, followed by a rapid collapse of the entire plant. Plant death quickly proceeds across a field.Pythiumspp. cause a watersoaked, brown root rot.Acremoniumcauses corky bands on primary and secondary roots. Infected roots are straw colored or slightly darker than healthy roots.Rhizopycniscauses a reddish tinge to the upper tap root. Infected tissue may be corky.

Tipburn is characterized bybrowning of the marginsof young, maturing leaves in head and leaf lettuces. The brown area may be limited to a few small spots at or near the leaf margin, or the entire edge of the leaf may be affected. Many pinpoint necrotic areas along the margin may give that tissue aspeckled appearance. Brown veins may occur near the brown lesions.

Symptoms on tomato plants infected withTobacco mosaic virusvary with the cultivar and the specific virus or strain. A mild mosaic develops on leaves with some leaf malformation, including a fernlike appearance. During cool weathershoestringlike symptomsappear on leaves, which is also characteristic ofCucumber mosaic virusin tomato. Necrotic patterns may develop on fruit.

Symptoms on eggplants infected withTobacco mosaic virusvary with the cultivar and the specific virus or strain. A mild mosaic develops on leaves with some leaf malformation, including a fernlike appearance. During cool weathershoestringlike symptomsappear on leaves, which is also characteristic ofCucumber mosaic virusin tomato. Necrotic patterns may develop on fruit.

Downward curling of leaf blades on tomato plants with tobacco streak is common. Leaf veins become necrotic and can lead to necrotic blotches, especially on young leaves. Fruit may develop necrotic ringspots.Necrotic streakson young stems extend to flowers and leads to flower drop.

Symptoms on plants infected withTobacco mosaic tobamovirusesand other tobamoviruses vary with specific viruses or strains, and depend on the temperature, light intensity, day length, and age of the plant. Symptoms can include necrosis on any plant part, defoliation, leaf distortion, and mosaic symptoms on leaves, stems, and fruit.

The most striking symptom of tomato big bud is the large,swollen green budsthat fail to develop normally and do not set fruit. Apical stems are thick and assume an upright growth habit. Infected plants appear bushy because of shortened internodes and small leaves. Leaves are distorted and yellow-green. Aerial roots may develop on stems.

Leaves on plants infected withTomato bushy stunt virusare small in size, cupped, and curled downward. The youngest leaves are twisted and exhibit tip necrosis. A proliferation of lateral shoots leads to an overall bushy appearance. Lower leaves are chlorotic with a purple tinge. Plants may be stunted. Fruit yield is greatly reduced.

The leaves of plants infected withTomato infectious chlorosis virusbecome yellow or red between the veins, stunted, and rolled. Symptoms generally occur on older leaves, while new growth continues to appear normal. As the disease progresses, interveinal necrosis can occur and the leaves become characteristically brittle, thick, and crisp.

Tomato pith necrosis affects mature tomato plants. Symptoms include a brown discoloration and necrosis of the pith, which eventually leads to hollow chambers in the stem. The pith browning usually extends far up the plant. Profuse adventitious roots are associated with the stem where the pith is affected. Gray or dark brown lesions may appear on the surface of the stem. Affected plants may turn chlorotic and wilt.

Plants infected withTomato spotted wilt virusexhibit bronzing of the upper sides of young leaves, which later develop distinct,necrotic spots. Leaves may be cupped downward. Some tip dieback may occur. On ripe fruit chlorotic spots and blotches appear, often with concentric rings.Green fruitshow slightly raised areas with faint, concentric zones.

Tomato yellow leaf curl is a disease of tomato caused byTomato yellow leaf curl virus.In March 2007, it was identified for the first time in California and currently has a limited distribution. Aneducational brochure(PDF)was created at that time and is available to print.Infected tomato plants initially show stunted and erect or upright plant growth; plants infected at an early stage of growth will show severe stunting. However, the most diagnostic symptoms are those in leaves.Leaves of infected

Tomato spotted wilt virusandImpatiens necrotic spot virusare closely related tospoviruses that cause indistinguishable symptoms in lettuce. Leaves of infected plants develop brown to dark brown spots and dead (necrotic) areas. Necrotic tissue can resemble burn damage caused by fertilizer or pesticide applications. As necrosis spreads, much of the leaf browns, dries out, and dies. Leaf yellowing, brown spots, and leaf deformity can be observed on both older and newer leaves. Margins of leaves may

Early symptoms of turnip mosaic include numerous small, light green, circular and irregular lesions on leaves. Later symptoms include veinal chlorosis, curvature of the midrib, asymmetrical distortion of the leaf blade, and necrosis of lower leaves. Lettuce infected early may be severely stunted, and can result in unmarketable heads.

Varnish spot affects only the inner leaves of head lettuce varieties. To see the symptoms, remove the outer leaves of the head. Varnish spot appears as dark brown, shiny, firm, necrotic lesions on these inner leaves. Lesion size can range from small to very large. Lesion borders are not delimited by veins, but areas along veins are most often affected. In severe cases, an infected leaf may have 90% or more of its surface area diseased. A notable feature of these lesions is that affected leaf tis

Yellowing between veins/wilting in heat

No cure - remove plants

Vine decline of melons, caused by the root-infecting ascomyceteMonosporascus cannonballus,is characterized by the sudden and generally uniformcanopy collapseof entire fields 1 to 2 weeks before harvest. The most susceptible hosts are cantaloupe and watermelon and, to a lesser extent, honeydew melons. The disease is particularly severe in the hot and semi-arid production regions of the world.In California, the disease is most prevalent in the Imperial Valley, Coachella Valley and the Palo Verde V

Symptoms of various virus diseases often resemble each other and may be difficult to differentiate in the field. Virus-infected leaves exhibit chlorosis, necrotic spots, mosaics, ringspots, mottling, crinkling (puckering), and other symptoms. Some viruses cause stunting and poor overall growth.Symptoms ofCucumber mosaic virusinfection on spinach include a slight chlorosis of younger leaves and narrow or "puckered" young leaves. Leaves also can have an inward rolling of margins. In advanced

Water-soaked lesions develop on ripe fruit in contact with wet soil. Within several days, the entire infected fruit turns into a water bag.

White mold generally appears on tomato plants at flowering. Symptoms include water-soaked areas on flowers and at stem joints where senescent flower petals have fallen. The infection quickly kills stems, which eventually dry and take on a bleached appearance. Water-soaked stem lesions may also appear at the soil line if senescent plant debris is present around the plant. Affected areas generally show white, cottony mycelium that soon produces large, irregularly shaped,black sclerotia. Infected f

The fungus infects leaves and floral parts, causing distinctive white, raised pustules to form underneath the plant epidermis. These blisterlike pustules sometimes result in twisted, deformed growth of the stem, leaves, or flowers. When mature, the epidermis covering the pustule will rupture, releasing powdery white sporangia (a type of spore) that can be carried by winds or splashing water onto neighboring host plants. Severely infected leaves can wither and die.

This fungus causes circular, light tan leaf spots that are up to 0.5 inch in diameter. Sometimes dark streaks and splotches develop in the spots. If conditions are favorable, the characteristic white growth of spores may be observed on the leaf spots.

Crown leaves become bright yellow and margins become necrotic. Leaves are stunted and misshapened.Symptomsmove out the runners until the entire plant is affected. Fruit set is eliminated and plants may be killed.