This past week there were a few reported cases of bacteria causing problems in tomato transplants, along with an isolated case of pith necrosis from the field as well as bacteria causing issues in strawberry. There have been no reports of late blight or cucurbit downy mildew in the region to date.
Cucumber/Pickles
Angular leaf spot – Symptoms are distinct and easily diagnosed. Small water-soaked lesions develop on leaves and expand until they are delimited by larger secondary veins in leaves resulting in angular lesions. After time these lesions turn brown and infected tissue drops-off resulting in ‘shotholes’. Angular leaf spot can be spread by splashing rain, insects, on the hands of workers and on farm machinery. Working in the field when the foliage is wet favors the spread of the disease. The disease can also be spread by blowing wind and in irrigation water. Management of angular leaf spot begins with clean-seed and planting in fields that has been out of cucurbit production for at least 2 years. Cultivating when foliage and soil are wet and irrigating with pond water should be avoided. There are cucumber varieties with resistance. Add label rate of fixed copper + mancozeb to fungicide maintenance program and repeat applications every 7 days.
Lettuce
Bottom Rot/Drop – Spring lettuce season is beginning and growers should take precautions to help control Bottom rot (Rhizoctonia) and Lettuce drop (Sclerotinia) which may cause potential problems. For Bottom rot, apply Endura 70W (boscalid, FRAC code 7) at 8.0 to 11.0 oz 70W/A, or iprodione (FRAC code 2) at 1.5 to 2.0 lb 50WP/A or OLF should be applied one week after transplanting or thinning and 10 and 20 days later. For Lettuce drop, apply Cannonball (fludioxonil, 12) at 7.0 oz 50WP/A (0 day PHI); Endura (FRAC code 7) at 8.0 to 11.0 oz 70WG/A (14 day PHI); or iprodione (FRAC code 2) at 1.5 to 2.0 lb/A (14 DAY PHI); or Quadris (azoxystrobin, 11) at 0.40 – 0.80 fl. oz/1000 row ft. 2.08SC (0 day PHI) beginning one week after transplanting or thinning and again at 10 and 20 days later. Check labels for days to harvest intervals. For more information on control of Bottom rot and Lettuce drop and other important diseases of lettuce please see the 2013 New Jersey Commercial Vegetable Production Recommendations Guide.
Tomato
Stem Rot/Pith Necrosis – Symptoms begin to develop as green fruit begins to mature. Bacteria are most likely ubiquitous to tomato fields and develop when weather conditions and cultural practices lead to favorable conditions for disease development. Symptoms include the development of irregular brown lesions on main stems and branches. Late pruning (i.e., suckering) can provide entry points for both bacterial diseases, especially during wet conditions. Internally, stems will become brown and mushy. High humidity is necessary for disease development in both cases. High nitrogen and low night temperatures are associated with Pith Necrosis development. Control of both begins with cultural practices such as avoiding working in fields with wet foliage, avoiding late pruning and watching the amount of N applied to plantings.
Bacterial spot and speck – Tomato transplants with suspected symptoms can be treated with streptomycin (Agri-Mycin 17, Agri-Strep, 25) at 1 lb/100 gallons, or 1.25 teaspoon per gallon every 4 to 5 days prior to transplanting. Additionally, Kocide 3000 (copper hydroxide, FRAC code M1) has a greenhouse label for speck and spot control in the greenhouse. Apply ½ to 1.5 TBSP per 1000 sq ft. every 5 to 10 days. Remember, phytoxicity is an important issue when apply copper in enclosed structures, see label for cautions, restrictions and liabilities. After transplanting, apply Actigard at 0.33 oz 50WG/A (see label for use), or fixed copper (M1) at 1 lb a.i./A plus a mancozeb (Dithane, Manzate, Penncozeb, M3) at 1.5 lb 75DF or OLF, or ManKocide (M1 + M3) at 2.5 to 5.0 lb 61WP/A on a 7 day schedule.
Strawberry
Angular leaf spot – Bacterial leaf spot can cause spots on the leaves causing them to die. Infections can also become systemic killing the whole plant. Importantly, the calyx can become infected causing them it prematurely turn brown and reduce marketability of fruit. Fixed coppers applications will help suppress the spread as long as the weather remains dry. Discontinue copper applications in plant injury begins to occur, usually after 4 to 5 applications. Avoid overhead irrigation which will only make problem worse.
