Andy Wyenandt

Potato

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.

• No basil downy mildew has been reported in the field to date in New Jersey. However, with current weather conditions expected all week, all basil growers should consider scouting on a daily basis and consider taking appropriate preventative measures.
• Cucurbit downy mildew has been reported on cucumber as far north as central North Carolina as of 6/9. To track cucurbit downy mildew in the US please visit http://cdm.ipmpipe.org/
• No late blight has been reported in the region and has only been found as far north as central Florida to-date. To track late blight in the US please visit http://usablight.org/.
• P-days for the first application for Early blight control in potato are quickly approaching the 300 threshold.
• The rainy and wet conditions expected most of this week make it ideal conditions for the spread of bacterial diseases in tomatoes and peppers. Take measures to avoid working in fields (i.e., staking and tying) when leaves are wet. Remember, the process of staking and tying creates wounds on leaves and stems which allow entry points for bacteria (and fungi) to enter the plant.

• Phytophthora blight is being reported in summer squash
• Angular leaf spot in cucurbits is wide spread in some areas
• Pythium and Rhizoctonia root rot have been reported in tomato and eggplant transplants
• Cucurbit downy mildew has been reported on cucumber as far north as Southern Georgia. To track cucurbit downy mildew in the US please visit http://cdm.ipmpipe.org/
• No late blight has been reported in the region to date and has only been found as far north as central Florida to-date. To track late blight in the US please visit http://usablight.org/

Pepper

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 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 2014 New Jersey Commercial Vegetable Production Recommendations Guide for more information.

Tomato

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, 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.