1. Fungal diseases of vegetables
Tomato
Vaishali S.Patil
Professor, Department of Botany
Shri Shivaji College of Arts, Commerce & Science
Akola
2. 1.Alternaria stem canker caused by Alternaria
alternata f.sp. Lycopersici
Symptoms-Dark brown cankers with concentric rings form on stems and
are often associated with wound sites. These cankers may enlarge,
eventually girdling the stem and killing the plant. A brown, dry rot
develops and brown streaks can extend into the pith above and below
the cankers. A toxin produced by the fungus growing in the stem
canker moves into the upper part of the plant, killing the interveinal
leaf tissue. As the disease progresses, curling of leaf margins and
eventual death of the leaf occurs. Fruit symptoms initially appear as
small, gray flecks which later enlarge and become dark and sunken
with the characteristic concentric rings.
Control: Resistant varieties should be used.
3. 2.Anthracnose caused by Colletotrichum coccodes,
Colletotrichum dematium, Colletotrichum gloeosporioides,
Glomerella cingulata
Symptoms- On ripe fruit small, sunken, circular spots appear.
The center of older spots later become blackish. Spots may
become numerous in severe cases, and secondary rotting
organisms may invade anthracnose lesions to completely rot
infected fruit. The fungus forms small, dark survival structures
called sclerotia in the centers of fruit spots.
Control: Harvest fruit as soon as possible after ripening.
Avoid excessive overhead irrigation or use drip irrigation, use
of fungicides, crop rotation.
4. 3. Black mold rot- caused by Alternaria alternata,
Stemphylium botryosum, Pleospora tarda, Stemphylium
herbarum, Pleospora herbarum, Pleospora lycopersici,
Ulocladium consortiale, Stemphylium consortiale
Symptoms-black lesions known as blossom end rot appear on
fruit & on the stem. Lesions may look shallow and superficial
or sink deep into the inner fruit which turns dark black.
Control: fungicides
5. 4.Black root rot caused by Thielaviopsis basicola,
Chalara elegans
Symptoms-Stunting, yellowing of leaves, and lack of
vigorous growth. Roots of affected plants had
numerous small, brown lesions.
Control: -Maintaining a soil pH below 5.6, removing
and destroying all diseased plants, using soil-less
media, sterilizing equipment, keeping work areas
clean, and controlling fungus gnats and shore flies,
“crop rotation, soil fumigants.
6. 5.Black shoulder caused by Alternaria alternata
Symptoms-on leaves as spots that range in size from
tiny to the width of thumb. They are usually yellow or
brown and once they appear, they spread rapidly in
concentric rings of darkening color. Spots usually
transfer or begin appearing on fruit and seed pods at
about the time they appear on leaves.
Control: infected plants should never be composted,
fed to livestock, or otherwise consumed,wider spacing,
clear weeding, and plant staking to allow air flow, use
of organic fungicide.
7. 6. Buckeye rot of tomato caused by Phytophthora capsici
Phytophthora drechsleri, Phytophthora nicotianae var.
Parasitica, Phytophthora parasitica
Symptoms- grayish-green or brownish, water-soaked spots
developing on fruit. The spot rapidly enlarges to cover up to
half of the fruit diameter. The rot then appears brown with
concentric rings.
Control: site selection, staking, mulching, cultural practices,
crop rotation, fungicides.
8. 7.Cercospora leaf mold caused by Pseudocercospora
fuligena, Cercospora fuligena
Symptoms- chlorotic (yellow) lesions which are
visible on the upper side of the leaf that later expands
to form a brownish lesion surrounded by a yellow
halo. When the humidity is high, gray to blackish-gray
fungal sporulation occurs on the lower leaf surface.
When the disease is severe the lesions will coalesce,
resulting in the collapse of the leaf tissues.
Control: sanitation, crop rotation till and fungicides
9. 8. Charcoal rot caused by Macrophomina phaseolina
Symptoms- On seedlings, black, sunken cankers may appear on
hypocotyls at the time of emergence. These cankers may develop a
concentric ring pattern, stunt affected plants and cause wilt. When older
plants are attacked, runners and crown leaves may turn yellow and die.
Typically, a water-soaked lesion will occur at the soil level and extend
several centimeters up the stem. Brown, water-soaked lesions are also
symptomatic of fruit infection. Amber-colored droplets of exudate may
form within the affected area. Eventually, the lesion dries up, turns light
tan and microsclerotia form.
Control: Manage irrigation to avoid drought stress. If soil salinity is
high, leach to reduce salt buildup. Drip irrigation may result in higher
soil salinity compared to furrow irrigation if salinity of the irrigation
water is moderate to high. Destroy
or deep-plow all plant debris at the
end of the season, a three-year rotation.
10. 9. Corky root rot caused by Pyrenochaeta lycopersici
Symptoms-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.
Control: Cultural practices, soil fumigation on fields, plant
when soils are warm in spring, avoid consecutive crops, soil
solarization, rotate with nonhost crops, use of metam sodium.
11. 10. Didymella stem rot caused by Didymella lycopersici
Symptoms-The lesions can be noticed as dark sunken and usually girdle
the stem. The entire plants can turn yellow and wilt. Fruiting bodies of
the fungus (pycnidia) are black in color and numerous on lesions. As the
wilting progresses, the plant may eventually die. Numerous black specks
(pycnidia), which are the fruiting structures of the fungus, frequently
form in the darkened stem lesions. Fruit infection typically occurs at the
calyx end and starts as a water soaked lesion that progresses rapidly into
a sunken black lesion with concentric rings. Leaf infection begins as
small spots, which develop into brown lesions with concentric rings.
Pycnidia may develop in the center of these lesions with the leaf
eventually taking on a shot hole appearance, or dying.
Control: Fungicide, sanitation ,
three-year rotation, avoid overhead
irrigation and provide adequate
Ventilation.
12. 11. Early blight caused by Alternaria solani
Symptom-Extensive defoliation from early blight exposes fruit to
sunscald and increases fruit rot. It also attacks stems and fruit. Dark
brown cankers may develop on stems and girdle stems of seedlings at the
soil line. Stem lesions on older plants usually remain confined to one
side of the stem. Infected leaves show circular spots (lesions) that are
brown and have a pattern of concentric rings imparting a “target-like”
appearance to the spot. The leaf area surrounding these spots may turn
yellow. Infected leaves eventually turn brown and drop from the plant.
Defoliation progresses upward from the lower plant. Sunken, dry lesions
occur most frequently on the stem end of the fruit and also have a zonate
or “target-like” appearance.
Control: Crop rotation. Avoid prolonged wetting of leaves from
irrigation or use drip irrigation.
Maintain adequate,
but not excessive, soil fertility.
Use of proper fungicide.
13. 12. Fusarium crown and root rot caused by Fusarium
oxysporum f.sp. radicis-lycopersici
Symptom-brown vascular tissue in stem from crown to
slightly above; stem surface can be brown; roots are brown
and rotting.
Control: Use disease-free transplants, avoid over watering,
disinfect transplant trays by steaming, use a preplant
fumigant, avoid injuring transplants, rotate with a
nonsusceptible crop, use of biological control, cover crops,
and soil solarization alone or in combination with fumigants.
14. 13. Fusarium wilt caused by Fusarium oxysporum f.sp.
Lycopersici
Symptom -A yellowing of the lower leaves, which gradually
wilt and die. The disease progresses up the stem until all of the
foliage is killed and the plant dies. If stems or petioles from
wilted areas of diseased plants are cut, a reddish-brown
discoloration can be seen between the pith (center of the stem)
and the outer green part of the stem. It is soilborn & seedborne
disease.
Control: Use of resistant varieties, crop rotation
15. 14. Gray Leaf Spot caused by Stemphylium botryosum f.sp.
Lycopersici, Stemphylium lycopersici, Stemphylium
floridanum, Stemphylium solani
Symptoms- Small brownish-black flecks that extend to both
sides of the leaf. Spots may be bordered by a narrow yellow
halo. As the spots enlarge, the central portion becomes gray,
cracks and falls out imparting a shot-hole appearance to
affected leaves. Leaves with numerous spots turn yellow and
drop to the ground.
Control: Use of susceptible variety, cultural and chemical
controls.
16. 15. Gray mold caused by Botrytis cinerea, Botryotinia
fuckeliana
symptoms: Tan or gray lesions typically form at the tips of
leaflets and become covered with brown or gray fungal
growth. Dead flowers and dying calyx tissue may also
become infected. Stem cankers may also develop. Typically
large, brown cankers may girdle the stem, causing wilting and
plant death above the canker. The production of “ghost spots,”
small, whitish rings or halos that develop on the fruit. Fruit
that does become infected becomes water-soaked and soft.
Control: reduce leaf wetness, proper pruning, sanitation,
fungicides
17. 16. Late blight caused by Phytophthora infestans
Symptoms- appear on the upper surface of leaves as greasy,
gray spots that expand rapidly. White mold usually develops at
the margins of affected areas. If stems and petioles are
infected, areas above these infections wilt and die. Entire
plants may be rapidly defoliated when conditions favor the
disease. Fruit infections begin as brown, greasy spots that
rapidly expand to rot the entire fruit.
Control: Dead vines from previous crops should be removed
or destroyed, avoid use of sprinkler irrigation, use of
fungicide.
18. 17. Leaf mold caused by Fulvia fulva, Cladosporium fulvum
symptoms are pale green or yellowish spots on the upper leaf surface,
which enlarge and turn a distinctive yellow. The spots on the lower leaf
surfaces become covered with a gray, velvety growth of the spores
produced by the fungus. When infection is severe, the spots coalesce,
and the foliage is killed. Occasionally, the fungus attacks stems,
blossoms and fruits. Green and mature fruit can have a black, leathery rot
on the stem end.
Control: Crop residue should be removed from the field. Staking and
pruning to increase air circulation, avoid wetting leaves when watering,
crop rotation, use of fungicide.
19. 18. Phoma rot caused by Phoma destructiva
symptoms -In its earliest stages, green fruit is marked by minute, slightly
sunken spots. As these spots enlarge they develop brown or black
borders with slightly lighter centers which become dotted with black
pimple-like bodies (pycnidia) in which the seedlike bodies, or spores, of
the fungus are borne.On the plant; spots are seen on the leaves,
leaf petioles, and the stems of the vines. Spotted leaves dry out and are
shed. In the early stages the spots on the leaves are mereiy small
discolored areas, later turning brown or black, which are definite in
outline. These spots enlarge, and often several merge into a large blotch.
On petioles and stems the diseased areas appear as streaks or blotches.
Control: fungicide, Crop rotations, disease-free seed, diseased parts are
cut away.
20. 19. Powdery mildew caused by Oidiopsis sicula, Leveillula
taurica
symptoms: Powdery white patches of
fungal mycelium develop on the upper surfaces of infected
leaves. These leaves may become chlorotic and eventually
necrotic. Light green or bright yellow, irregularly shaped
lesions typically appear on the upper surfaces.
Control: resistance, fungicides
21. 20. Pythium damping-off and fruit rot caused by Pythium
aphanidermatum, Pythium arrhenomanes, Pythium
debaryanum, Pythium myriotylum, Pythium ultimum
Symptom- A small water-soaked spot appear on fruit. At
severity the entire fruit becomes rotted, the skin ruptures and
the watery contents of the fruit spill out. A white, cottony
growth may be observed within rotted areas of the fruit.
Control: Start seeds indoors in sterilized potting mix.
Do not start seeds in soil that has a high nitrogen level. Add
nitrogen fertilizer after the seedlings have produced their first
true leaves. Allow the surface of the soil to dry between
waterings.
22. 21. Rhizoctonia damping-off and fruit rot caused by
Rhizoctonia solani,Thanatephorus cucumeris
Symptom- Alternating light- and dark brown colored zonate
bands and sharply defined margins appear on fruits. The rot
may be firm at first, but later, affected fruit becomes mushy.
Control: Avoid planting tomatoes in poorly drained soils or
in low areas of a field. Mulching with plastic film or with
organic matter to keep fruit from contacting the soil and/or to
reduce soil splashing onto fruit will reduce the chance of soil
rot infection. Use of fungicide spray.
23. 22. Rhizopus rot caused by Rhizopus stolonifer
Symptom-water soaked regions on the fruit leading to
puffy white growth that collapses the outer fruit tissue.
The white fungal mycelia can be noticed with large
masses of black mustard like spores on raised stalks.
Control: Postharvest fungicide applications are
effective. Avoid injuring fruit during harvesting and
handling and maintain proper temperature control
during storage and transit.
24. 23. Septoria leaf spot caused by Septoria lycopersici
Symptom-The disease first appears on the lower leaves after
the plant has set fruit. Leaf spots begin as yellow areas that
later become circular with gray centers and dark borders.
Spots surrounded by a yellow halo. Tiny black specks may
develop in the center of these spots. These are fruiting
structures that release spores. Severely infected leaves fall off.
Defoliation progresses from the base of the plant upwards.
Loss of foliage may cause fruits to become sunscalded.
Control: Crop rotation, removal of plant residue, Weed
control, use of proper fungicide.
25. 24. Sour rot caused by Geotrichum candidum, Galactomyces geotrichum,
Geotrichum klebahnii (= G. penicillatum)
Symptom-It usually begins at the stem scar and may extend in sectors down the side of
the fruit. A dull white fungal growth may occur where the epidermis cracks. The fruit
often remains firm until the rot is advanced, and then a sour odor develops.
Control: Avoid fruit injury, especially at harvest. Cultural methods, which keep fruit
from coming in contact with the soil, help prevent many of the fruit rots. Improve air
movement in the field by orienting planting rows in the direction of prevailing winds,
and use proper row and plant spacing to shorten the length of time that the fruit remains
wet. Schedule sprinkler irrigation to minimize the length of time that free water remains
on the fruit. Fungicides may offer some protection against some fruit rots. Firm fruited,
crack-resistant varieties may escape infection by some fruit rots.
26. 25. Southern Blight caused by Sclerotium rolfsii, Athelia
rolfsii
Symptom- Rapid wilting of the entire plant take place. A
water-soaked lesion on the stem near the soil line rapidly
expands, turns brown and girdles the stem. A white mold
(mycelium) eventually covers the stem lesion and surrounding
moist soil. Sclerotia form on the mycelium which is first
white, later becoming brown. It is soilborn disease.
Control: Crop rotation, use of fungicide, removal of plant
residues.
27. 26. Target spot caused by Corynespora cassiicola
Symptoms on leaflets begin as small, water-soaked lesions
that expand and become light brown and circular. These
lesions often develop a target-like appearance. Yellow halos
develop around individual lesions. Lesions may coalesce and
result in the collapse of leaflet tissue. Similar lesions develop
on petioles and stems, but these are more elongate than those
on leaves. These lesions may girdle petioles and stems and
result in leaflet or leaf collapse. On young fruit, lesions begin
as brown, sunken spots the size of a pinpoint, but they can
develop into craters. On ripe fruit, large, circular lesions with
brown centers can develop. A crack often develops in the
centers of the lesions on ripe
fruit.
Control: Fungicides
28. 27. Verticillium wilt caused by Verticillium albo-atrum,
Verticillium dahliae
Symptom- They block the vascular tissue in the plant and
cause the leaves and stems to wilt. Symptoms progress slowly,
often one stem at a time. Eventually, the entire plant yellows
and withers.
Control: Plant only resistant varieties. Soil solarization will
help kill the fungal spores, crop rotation.
29. 28. White mold caused by Sclerotinia sclerotiorum,
Sclerotinia minor
Symptoms: Water-soaked areas near leaf axils or in stem
joints are form. Stems become soft once infected and
eventually become light gray or tan and have a bleached
appearance. Mycelium often develops on or in infected stems.
Black sclerotia that look like rat droppings are often present on
the fungal mycelium or inside infected stems. These sclerotia
are typically black on the outside and white on the inside.
Infected fruits typically turn gray and develop a watery rot.
The characteristic white fungal mycelium and black sclerotia
may also develop on infected fruits.
Control: cultural practices,
deep-plowing,
fungicides.
