VegNet Vol.
11, No. 12.
On the WEB at: http://vegnet.osu.edu
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this fax, Call 614-292-3857
In This Issue
1. Cucumber
Downy Mildew
2. OFFER
Twilight Tour
Cucumber
Downy Mildew by Gerald J. Holmes, Associate Professor & Extension Vegetable
Pathologist, Department of Plant Pathology North Carolina State University
Information provided by: "Christian A. Wyenandt",
wyenandt@AESOP.Rutgers.edu
Colleagues,
Just a quick note to make you aware of a situation that could be
coming your way. We are currently going through the worst epidemic of downy mildew
on cucumber that anybody here can remember seeing. Four things about this
epidemic are noteworthy: 1) it arrived about 6 weeks earlier than usual; 2) it
is more severe than usual on cucumber; 3) it is only causing a problem on
cucumber (a couple reports on melon); 4) it has not been reported from SC or
GA. Typically we can grow our spring cucumber crop without fungicides.
Even in the fall, when DM is around and causing problems on pumpkins and
squash, it is not much of a concern on cucumber. I have always attributed this
to excellent resistance in most cultivars. This year we have fields that were
abandoned before the first harvest because of DM. I was at a field day
yesterday (put on by our breeder Todd Wehner) and had
a chance to talk with several cucumber growers; most said they got 2-3 harvests
when they would normally get 5-6. It caught nearly everybody by surprise and
fungicides were not applied preventatively.
At this field day, Todd had 35 pickling cultivars and 28 long
green cultivars in a performance trial (replicated 3X). Although they had all
been treated with a Quadris--Kocide
rotation (not a particularly good selection but that's what the station superintendant did), there was plenty of disease present.
Most modern pickling cultivars looked good with 'Vlasstar'
and 'Jackson' holding up quite well. In the long greens, '
If the disease moves north (more likely than normal), I think the
key to controlling it will be disease-resistant cultivars and preventative
fungicide applications. Neither one alone will likely be
sufficient and chasing the disease once it gets started is usually a
losing proposition. As for fungicides, there are quite a few options: chlorothalonil, Tanos, Ridomil Gold Bravo, Cabrio,
Pristine and Gavel all have good activity against the disease in the south. I
am not hearing that any of these are working well right now in NC, but I don't
think they were used preventatively. Many growers reported using Quadris which I have not seen good results with in my
trials. Cabrio would be the better strobilurin to use. If you're interested, you can see this
in our efficacy table: http://ipm.ncsu.edu/agchem/chptr6/615.pdf
The following link has background information on Downy mildew in
cucurbits:
http://www.ces.ncsu.edu/depts/pp/cucurbit/
OFFER
Twilight Tour, OSU/OARDC’s Organic Food and Farming
Education and Research Program.
OARDC’s
Program: Introduction and Overview of OFFER Research:
Guests
choose which of the following two concurrent sessions they wish to attend:
Organic
Vegetable Research and Composting: 6:30 – 8:00 p.m. (Horticulture
Unit 1 and Fry Farm), Peri-Urban Vegetable Transition
Project – Year 2; Organic Composting (in partnership with OARDC’s
Ohio Composting and Manure Management Program); New Vegetable Variety
Experiment; Vegetable Transition Experiment – Year 4
Organic
Grains and Winter Squash Research:
New Corn Varieties; Small Grains - Hard Wheat, Spelt, High-Oil
Naked Oats; Compost Experiments – Year 6; Forage Crop Experiment Year 3; Corn New Giant Ragweed Control Experiment;
New Biological Buffering Research; Japanese Co-Op Soybean Marketing Research;
Field Crop Transition Experiment – Year 5; New Organic Disease Management for
Winter Squash
Groups
re-join: Organic Strawberry Research and Food Tasting: