Bacterial leaf spot – Symptoms of bacterial leaf spot on pepper leaves include small, brown water-soaked lesions that turn brown and necrotic in the centers. Spots may coalesce and form large blighted areas on leaves and premature defoliation can occur. On fruit, brown lesions can form which have a roughened, cracked wart-like appearance. High temperatures, high relative humidity and rainfall favor Bacterial spot development. Loss from Bacterial spot can be reduced somewhat by maintaining high levels of fertility, which will stimulate new growth. Applying a fixed copper (M1) at labeled rates or may help suppress spread. Quintec (quinoxyfen, 13) at 6.0 fl. oz/A is now labeled for the suppression of bacterial leaf spot in pepper in the mid-Atlantic region. Please see the 2015 New Jersey Commercial Vegetable Production Recommendations Guide for more information.
Pepper and Tomato
For control of the crown rot phase of Phytophthora blight, apply:
- mefenoxam–1.0 pt Ridomil Gold 4SL/A or 1.0 qt Ultra Flourish 2E/A or metalaxyl (MetaStar)–4.0-8.0 pt 2E/A at transplanting and 30 days later
- Presidio (fluopicolide, 43) at 3.0-4.0 fl. oz 4SC/A at transplanting and/or 14 days later (between two mefenoxam applications),
- Ranman (cyazofamid, 21) at 2.75 fl oz 400SC at transplanting (Ranman may be added to transplant water, see label for restrictions) and/or 14 days later (between two mefenoxam applications),
Phosphite materials (FRAC code 33) such as Rampart, ProPhyt, K-Khite may also be tank mixed with one of the above to help suppress Phytophthora blight.
Growers with a known history of mefenoxam-insensititivity on their farm should use Presidio or Ranman plus a Phosphite fungicide in rotation. If mefenoxam has not been used in particular fields on any crop for a number of years (more than 5+) the fungus may revert back to being mefenoxam-sensitive.
Organic bell pepper growers with a history of the Phytophthora blight should plant cultivars that have resistance or tolerance to the disease. Long non-host crop rotations are critically important for organic production. Regular applications of Double Nickel (Bacillus amyloliquefaciens) or Regalia (Extract of Reynoutria sachalinensis) as drenches or via the drip system prior to the onset of disease may help suppress Phytophthora blight development.
Black Leg – Black leg is caused by Erwinia spp. which also cause ‘soft rots’. The bacteria which lead to the aerial phase of Blackleg are soil-borne (originate from old crop debris) and spread by rainfall, overhead irrigation and wind. The aerial phase of Blackleg does not originate from decaying seed pieces. The bacterium can enter the plant through wounds created by cultivation or through stems damaged by blowing wind, sand or hail. Dense canopies, warm weather and prolonged periods of leaf wetness favor the spread of aerial Blackleg. Fortunately, the disease rarely extends below ground and only causes dieback of stems over time. Symptoms of the aerial phase of Blackleg first appear as an irregular, water-soaked ‘green’ decay on stems that turns light-brown to black over time. Hot, dry weather will cause infected areas to dry out and become brittle. Do any cultivating when plants are dry, cultivating in the presence of dew or wet plants may help to spread the bacterium around.
Leather rot – can infect fruit at any stage. On green fruit, infected areas turn a dark-brown and develop a rough ‘leathery’ appearance. On fully mature (red) fruit little or no color change may occur on infected fruit however, fruit will have an unpleasant smell and taste. The pathogen (Phytophthora cactorum) overwinters in the soil in low-lying spots and becomes active during wet weather. Conditions that favor leather rot development also favor grey mold (Botrytis) development. However, fungicides for Grey mold control are not effective for leather rot control. Applications of a FRAC group 4 fungicide, such as Ridomil Gold SL (mefenoxam) at 1.0 pt/A 4SL or MetaStar (metalaxyl), or phosphite fungicide (FRAC code 33 fungicide), such as K-Phite, Rampart, or ProPhyt, prior to or at harvesting will help suppress leather rot. For more information on controlling leather rot and other important diseases of strawberry please see the 2015 New Jersey Commercial Vegetable Production Recommendations Guide.
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.
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, phytotoxicity 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, 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.