Vegetable Disease Update – September 23, 2011

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Lima Bean Downy Mildew
Downy mildew is present now in Delaware lima bean fields. Levels are not high but many have been sprayed to protect the crop. Keep scouting and apply fungicides when needed; see past issues and the 2011 Delaware Commercial Production Recommendations for more information.

Fall Sanitation
In vegetable production it is not a good idea to leave old crop residue in the field any longer than necessary. If the crop is allowed to survive after harvest, fungi that cause many diseases continue to increase on the surviving plants. This allows higher numbers of the fungus to potentially survive until next season. Sanitation (plowing or disking the old crop) will help prevent pathogen carry-over.

Nematodes in Veggies
Fall is the best time to soil sample for nematode pests such as root knot, lesion, and other plant parasitic nematodes. After fall harvest but before any fall tillage is done take soil cores six inches deep between plants in the row. Samples should be taken in the root zone of the old crop. Twenty cores/ sample should be taken from random spots in the field and placed in a plastic bucket gently mixed, and a pint of soil submitted for analysis. Large fields should be subdivided into blocks of 10-15 acres each and sampled separately. Nematodes are not uniformly distributed in the soil and it would be easy to miss significant numbers if a single sample of 20- 25 soil cores represented a large acreage. Nematode test bags and instructions are available for purchase from the county Extension offices. Samples cost $10.00. Fall sampling for root knot nematodes is strongly recommended for fields that will be planted in cucumbers, watermelons, cantaloupes, lima beans or other high value vegetables where root knot could reduce production. Forms and instructions are also available on the web at http://ag.udel.edu/extension/pdc/index.htm.

New video on nematode sampling
“How to Sample for Nematodes”
is a new video that was just produced to help growers with taking nematode samples in the fall to monitor plant parasitic nematode populations in their fields. The video features Bob Mulrooney, Extension Plant Pathologist at the University of Delaware explaining and demonstrating how to take soil sample for nematodes in row crops as well as narrow crop soybeans. The link for viewing is on the CANR You Tube server at http://youtu.be/x5HcY_L6aQk.

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