Archives for June 2014

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.