1. Solenaceous Crops II Root-knot nematode Bacterial Spot
Jan 26, 2009
Root-knot nematode
Bacterial Spot
Blossom End Rot/Sun Scald
**Not all images created by J. Bond**

2. 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

3. Pathogen Description Parasitic Roundworms
Early juvenile and Male stages are vermiform
Extreme Sexual Dimorphism
Female nematode is pear-shaped with egg masses attached at maturity

4. 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

5. Disease Symptoms
Field symptoms caused by Meloidogyne incognita, root knot nematode

6. Disease Symptoms
Root system heavily galled by root-knot nematode on the left and a health root system on the right.

7. 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

8. 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

9. Southern Root Knot Nematode
Not detected
Detected
Detected on soybean
Still counting

10. 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

11. 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.

12. Pathogen Life Cycle

13. Female
Egg mass
Microscopic view of root galling (arrows).

14. Control Measures
Use resistant cultivars; some populations may overcome resistance.
Practice crop rotation.
Use of soil fumigants or soil nematicides are effective for control.

15. Germplasm Evaluation

16. 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

17. 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

18. Disease Symptoms Bacterial Spot of Pepper Casual agent
Xanthomonas campsestris pv. vesicatora

19. Disease Symptoms Bacterial Spot of Tomato Casual agent
Xanthomonas campsestris pv. vesicatora

20. 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.

21. 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

22. 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.

23. Symptoms and Signs
Blossom end rot
Caused by calcium deficiency

24. Disease Symptoms
Blossom end rot is characterized by water-soaked areas that develop near the blossom end. The affected tissue desiccates, becoming brown and leathery. Affected pods may ripen prematurely. Secondary fungi and bacteria may colonize the dead tissue, causing it to turn dark and rot.
Blossom end rot is caused by a calcium deficiency in developing fruit. It occurs in fields with low or moderate soil calcium levels. Fluctuating soil moisture due to overwatering or drought, high nitrogen fertilization, and root pruning during cultiv ation are conducive to blossom end rot.

25. 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

26. 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

27. 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.

28. Disease Symptoms
Sunscald-damaged Bell Pepper. Lesion colonized by saporophytic fungi (dark appearance)