Transcript Jan 26, 2009 **Not all images created by J. Bond

Solenaceous Crops II
Jan 26, 2009
• Root-knot nematode
• Bacterial Spot
• Blossom End Rot/Sun Scald
**Not all images created by J. Bond**
Root Knot Nematode
• CROP: Tomato, Pepper, virtually all plants
• PATHOGENS:
• Meloidogyne incognita – Southern Root-knot
nematode
• M. hapla - Northern Root-knot nematode
• M. arenaria - Peanut Root-knot nematode
• DISTRIBUTION: Worldwide, IL
Pathogen Description
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•
•
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Parasitic Roundworms
Early juvenile and Male stages are vermiform
Extreme Sexual Dimorphism
Female nematode is pear-shaped with egg
masses attached at maturity
Disease Symptoms
- above ground: plants are
stunted with some yellowing
and severely affected plants
may wilt
- root system: galls are formed
on primary and secondary
roots; galls become large and
are very obvious
Disease Symptoms
Disease Symptoms
Pathogen Description
Sedentary endoparasite
Males can be rare, reproduction
by amphimixis and
parthenogenesis
Life cycle is 3 weeks to several
months depending on
environment, 4-5 cycles per
growing season
400 μm
Pathogen Description
Uses its stylet to pierce cell
walls to excrete enzymes for
infection and feeding
After feeding for a few days,
females release eggs in
gelatinous matrix
Southern Root Knot Nematode
Not detected
Detected
Detected on soybean
Still counting
Host Crops in Illinois
Row Crops
Corn, Soybean, Wheat, Oats, Barley, Sunflower, Canola, Buckwheat,
Pasture Grasses
Vegetable Crops
Asparagus, Beans and Peas, Beet, Carrot, and Parsnip, Cole Crops
(Broccoli, Cabbage, Collards, etc.), Cucurbit Crops (Cucumber,
Melons, Pumpkin, Squash), Lettuce, Spinach, and Other Greens,
Onions, Garlic, and Leeks, Potatoes, Sweet Corn, Sweet Potatoes,
Tomatoes, Peppers, and Eggplant
Fruit Crops
Apples, Blueberries, Brambles (Blackberries and Raspberries), Grapes,
Peaches, Strawberries
Virtually all ornamental plants
Conditions for Disease Development:
- the nematode has a wide host range; it can
also survive as dormant eggs a few months.
- warm temperatures and light sandy soils are
conducive for development.
Pathogen Life Cycle
Female
Egg mass
Control Measures
Use resistant cultivars; some populations may
overcome resistance.
Practice crop rotation.
Use of soil fumigants or soil nematicides are
effective for control.
Germplasm Evaluation
Disease: Bacterial Spot
CROP: Pepper, tomato, and many other crops
PATHOGEN: Xanthomonas campestris pv.
vesicatoria (strain specific)
DISTRIBUTION: Worldwide - IL
PATHOGEN DESCRIPTION: Gram-negative rod
DISEASE SYMPTOMS
Affects leaves, fruit, and stems
On leaves lesions begin as small water-soaked spots that remain small
and become necrotic with a chlorotic border. Lesions may be
sunken on the upper surface and raised on the lower surface.
On fruit raised, dark colored lesions are wart-like in appearance
On stems and petioles lesions appear as elongated necrotic spots or
streaks
Heavily infected leaves turn yellow and drop resulting in severe
defoliation
Disease Symptoms
Disease Symptoms
Conditions for Disease Development
Bacterium is seedborne and can survive in
infected crop debris
Many strains attack both tomato and pepper.
Disease is enhanced by overhead water, heavy
dew formation, and high temperatures.
Control Measures
Use pathogen-free seed and disease-free
transplants
Crop rotation
Resistant cultivars are becoming available, but
may not be resistant to all strains
Copper and copper + maneb sprays reduce damage
Rain shelters may reduce disease severity during
heavy rainfall periods
Physiological Disorders
BLOSSOM END ROT - Calcium deficiency and
water imbalance
DISEASE SYMPTOMS AND SIGNS:
A water-soaked lesion develops on the fruit lobe
near the blossom end. The lesion desiccates,
turns tan or brown, and becomes leathery in
appearance. Saprophytic fungi and soft rot
bacteria may invade the lesions.
Symptoms
and Signs
Disease Symptoms
Conditions for Disease Development
Soils with low calcium levels
Excessive or deficient soil moisture and high temperatures
Excessive nitrogen levels and root damage by cultivation
enhance blossom end rot development
Control Measures
Application of limestone to low pH soils and
gypsum (calcium sulfate) to high pH soils
with low calcium levels.
Good water management and proper nitrogen
applications
Avoid cultivation near the plant that causes root
damage
Sunscald - Fruit exposure to direct
sunlight
DISEASE SYMPTOMS AND SIGNS:
Pod wall tissue looses turger and rapidly dehydrates forming a papery,
bleached lesion on the side exposed to the sun. Discoloration may
occur later as secondary organisms invade.
CONDITIONS FOR DISEASE DEVELOPMENT:
- bright sun and exposure of fruit due to limb breakage by wind,
cultivation, or harvest Mature green fruit are most susceptible.
CONTROL MEASURES:
- care in harvesting and cultivation not to damage the plants.
- selection of cultivars with good foliage coverage.
Disease Symptoms