Disease Management

Tomato Pseudomonas Fruit

Bacterial Speck of Tomato

Bacterial speck occurs on tomato not pepper. It is a cosmopolitan disease, generally of minor concern, favored by low temperatures and high moisture. The bacterium Pseudomonas syringae pv tomato causes a fruit spot and foliage blight. This bacterium is also seedborne, spreads within fields in the same manner as bacterial spot, and may persist in weed species. Lesions on leaves are round and dark  brown to black with a halo that develops with time. Spots may coalesce, killing large areas of tissue. On fruit, small (1/16 inch), dark spots or specks develop with the tissue around them often more  intensely green than unaffected areas.

Management of Bacterial Spot and Bacterial Speck

Although the two bacteria are unrelated, their life histories and management strategies are similar.

1. Buy certified seed from a reputable source or use seed treatments to reduce transmission.
2. Produce disease-free 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 carry-over 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:

acibenzolar-S-methyl (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, KOP-Hydroxide):  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 (Tenn-Cop 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): 2-4 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): 0.75-1.5 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 (Agri-mycin 17): 200 ppm (REI 12 h). Use only up to transplant.

Prepared by M. Bess Dicklow, UMass Extension, Fernald Hall, University of Massachusetts, Amherst, MA 01003-9320. Tel 413-577-1827 Fax 413-545-2115. mbdicklo@umext.umass.edu.

Revised July 29, 2005 V4