Vol. 16, No. 13. June 22, 2009 The Ohio State University Extension Vegetable Crops On the WEB at: http://vegnet.osu.edu

In This Issue

1. cew

2. Update on Vine Crop Downy Mildew June 22, 2009

Update on Vine Crop Downy Mildew June 22, 2009

Sally Miller, Professor and State Extension Specialist, Department of Plant Pathology, OSU

Despite an erroneous report last week in a fungicide company newsletter, there have been no confirmed reports of downy mildew in cucumbers or other vine crops in the Fremont OH area or elsewhere in Ohio. Relatively high spore counts were found in one spore trap in northeast Monroe County, MI, but the disease has not been confirmed at this time. Sentinel plots have been planted in four locations in Ohio and we will continue to scout for downy mildew in these plots as well as in commercial fields.

If you are concerned that your cucumbers or other vine crops are showing symptoms of downy mildew, please send a sample to Sally Miller or Fulya Baysal-Gurel, Department of Plant Pathology, The Ohio State University, OARDC, 1680 Madison Ave., Wooster, OH 44691, ph. 330-263-3838, or to the C. Wayne Ellett Plant and Pest Diagnostic Clinic, OSU, Kottman Hall, 2021 Coffey Road, Columbus, OH 43210, ph. 614-292-5006 (c/o Nancy Taylor) for confirmation. Those in the Fremont area may prefer to take their samples to the OSU-OARDC North Central Agricultural Experiment Station, which is now equipped with microscopes connected to the OSU Wooster and Columbus labs via the internet, for confirmation.

Downy mildew appears to be on a course for appearance in Ohio in late June or early July as in the past 2 years, although a period of hot dry weather may slow it down considerably. Scout fields regularly for the first appearance of downy mildew symptoms. Downy mildew is favored by cool, moist conditions. Step up scouting under these conditions. Send samples to a lab for confirmation if downy mildew has not been reported in the area.

Fungicide application:

Protection before disease appears: Apply one of the following fungicides on a 7-10 day schedule, tank mixed with Bravo, Manzate or Dithane: Presidio, Ranman, Previcur Flex, Tanos, Curzate or Gavel. Alternate products. The application interval can be lengthened under dry conditions. Use the shorter interval under cool, moist conditions

Management after disease appears: Apply one of the following fungicides on a 5-7 day schedule, tank mixed with Bravo or Dithane: Presidio, Ranman, Previcur Flex, or Tanos. Alternate products. The application interval can be lengthened under dry conditions. Use the shorter interval under cool, moist conditions. See product labels for fungicide rates.

Most recent research has shown that fungicides can be ranked as follows for efficacy against downy mildew: Presidio = Ranman > Previcur Flex > Curzate > Gavel > Mancozeb = Bravo.

Note that the fungicides recommended above have different preharvest intervals (PHI). Keep this in mind as fungicides are applied after harvesting begins.

Product	PHI (days)
Bravo Weather Stik	0
Ranman	0
Previcur Flex	2
Tanos	3
Dithane or Manzate*	5
Gavel*	5
Presidio	2
Curzate	3

*labeled for cucumbers, melons, summer squash, watermelon (NOT pumpkin)