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**

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 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 Field symptoms caused by Meloidogyne incognita, root knot nematode

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

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 Microscopic view of root galling (arrows).

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 Bacterial Spot of Pepper Casual agent Xanthomonas campsestris pv. vesicatora

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

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 Blossom end rot Caused by calcium deficiency

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.

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