Downy Mildew Variety Trials at Twin Oaks Seed Farm

| 7/30/2014 10:49:00 AM

Seed harvest season is starting. Today was our first 2014 harvest of tomatoes and watermelon for seed. Things will start slowly, and by about the second week of August we will be swamped with tomatoes, muskmelons, watermelons and cucumbers.

I’ve been growing seeds at Twin Oaks for six years now, and have a pretty good idea of what to expect out of the harvest season, which for us runs from early August to late October.

This year though we have added a major new focus to our operation: variety trials, and lots of them. Last November I applied for a SARE grant to trial cucumber, muskmelon and winter squash, with a focus on Cucurbit Downy Mildew resistance, and we got the grant. We grow a lot of cucurbit family crops, and Downy Mildew has been the #1 problem we’ve encountered. This was especially true in 2013, when DM showed up on our farm in June. Downy Mildew overwinters in Florida, and blows north on the wind each year, thriving when the weather is wet. It starts with yellow spots on the leaves. The spots grow and turn brown and the leaf dies. DM can easily defoliate an entire field of a susceptible variety of cucumber, muskmelon, squash or gourds. Most commonly grown varieties are susceptible to current strains of DM. Our smaller observation trials in 2013 found that only a few varieties out of 35 muskmelons and 35 cucumbers were able to produce a crop under heavy DM pressure. Read more about Downy Mildew and about our 2013 trials here.

Our Winter Squash Trial (on July 22nd 2014):


If you live on the eastern US (especially the Southeast and Mid Atlantic) or in the eastern part of the Midwest, Downy Mildew is likely a significant problem for your cucumber, muskmelon and squash crops, at least in a high pressure year. If you live elsewhere in the US, Downy Mildew may be of academic interest but is probably not directly relevant to your garden.

8/5/2014 6:43:05 PM

I've used hydrogen peroxide for fungal and bacteria infections with great results. It now comes in spray bottles (Very convenient for small scale gardeners like me). Just add a few drops of a natural soap like Dr. Bronner's as a wetting agent, and spray on foliage in the evening when there's no chance of rain. Repeat if needed. this has worked wonders on peppers, cucumbers, and squash.

8/1/2014 12:35:46 PM

Downy Mildew is here. Its sure to spread with the rainy weather we're getting. Kind of happy about it and kind of not! Edmund on August 1st

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