Pepper Bacterial Spot Defoliation
BACTERIAL SPOT OF PEPPER
Bacterial spot caused by Xanthomonas campestris pv. vesicatora (Xcv) is present wherever tomato and peppers are grown. In general, Xanthomonas pathovars have narrow host ranges. Xcv consists of different strains that vary in their pathogenicity to tomato, pepper, and nightshade. The bacterium is able to survive on tomato volunteers and can overwinter in diseased plant debris. Seed is an important mechanism for survival and dissemination of Xcv. Disease development is favored by temperatures between 80° and 90° F and by heavy rainfall. The bacterium is spread by winddriven rain, workers, farm machinery, and aerosols. It penetrates through stomates and wounds created by insects, winddriven
sand, and tools. Xcv affects all aboveground plant parts. On leaves, the spots are generally brown, circular, and watersoaked.
Bacterial spot lesions do not have concentric zones or a prominent
halo. When conditions are optimal for disease development, spots can coalesce to form long, dark streaks. A general yellowing may appear on foliage with many lesions giving the plants a scorched appearance,
and the plants may exhibit severe epinasty. Only green tomato fruit is susceptible to infection and lesions are quite distinct, beginning as minute, slightly raised blisters with a halo that resemble the birdseye spot
caused by Clavibacter michiganense (bacterial canker). As lesions enlarge, they loose their halo and become brown, raised, and scablike.
Lesions on ripe pepper fruit may be scablike or sunken.
Management of Bacterial Spot
1. Buy certified seed from a reputable source or use seed treatments to reduce transmission.
2. Produce diseasefree
transplants by raising transplants in an area where production does not occur. Inspect all purchased transplants carefully and if transplants originate in southern states they should be certified.
3. Rotate fields to avoid carryover on volunteers or crop residue.
4. Keep fields free from volunteers, weeds, and cull piles.
5. Avoid working in fields when bacterial diseases are present and the fields are wet.
6. Apply appropriate bactericides or combination pesticides.
In general, bacterial diseases of field crops are difficult to control with pesticides; copper/mancozeb solutions are most effective When a significant amount of disease is present, pesticides are usually not effective.
Chemical recommendations:
- acibenzolarSmethyl (Actigard 50 WG): 0.3 to 0.75 oz/A (14 dh, REI 12 h).Do not apply more than six times per crop season or on less than a 7 day schedule. Under certain conditions, this product, when used on tomatoes, may lead to reductions in yield.
- copper hydroxide (Chanp, Champion WP): 4 tbs/1000 sq ft ( 0 dh, REI 24 h). Greenhouse and Shade house crops. Begin applications when disease first threatens and repeat at 7-10 day intervals as needed. Do not apply in a spray solution with pH less than 6.0 or phytotoxicity can occur.
- copper hydroxide (Kocide 2000, KOPHydroxide): 1.5 to 3.0 lb/A (0 dh, REI 24 h). Begin applications when disease first threatens and repeat at 5-10 day intervals. Use higher rates when conditions favor
disease development.
- copper salts of fatty acids (TennCop 5E): 3 pts/A. (0 dh, REI 12 h). Apply at the first sign of disease and repeat at 7-10 day intervals. Enhanced control obtained by tank mixing with Manzate 75 DF. Avoid
spray solution with pH of less than 6.5 as phytotoxicity may occur.
- copper sulfate monohydrate, tribasic (Basicop): 24 lb/A ( 0 dh, REI 24 h). Begin when disease normally appears and repeat at 7-10
day intervals. Use higher rate when disease pressure is heavy.
- ethylene bisdithiocarbamate plus manganese plus zinc (Manzate 75 DF): 0.751.5 lb/A (5 dh, REI 24 h). Start applications at transplant. Repeat at 3-7 day intervals throughout season. Do not apply more than 22.4 lbs per acre per crop.
- mancozeb plus copper hydroxide (ManKocide): 2.5 to 5.0 lb/A (5 dh, REI 24 h). Begin applications when disease threatens and repeat at 7-10 day intervals as needed. Use higher rates and 3-7 days when disease pressure is severe.
- streptomycin sulfate (Agrimycin 17): 200 ppm (REI 12 h). Use only up to transplant.
- M. Bess Dicklow.
Updated June 2006
Where trade names or commercial products are used, no company or product endorsement is implied or intended.
Always read the label before using any pesticide. The label is the legal document for product use. Disregard any
information in this newsletter if it is in conflict with the label.
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