[Market-farming] cucurbits

Shoemaker, William H wshoemak at illinois.edu
Sat Jan 30 21:25:14 EST 2016

I think the differences between C. pepo, C. moschata and C. maxima are fairly subtle, but they are there. Pepo seems a little tougher to me but a little more inclined to virus susceptibility. The weakness of maxima compared to the others is susceptibility to downy mildew. There may be other fungal pathogens that maxima is more susceptible to. The period of flowering in all of these pumpkin/winter squash types is a critical period. They become more susceptible to insects and diseases because a lot of energy gets diverted to producing fruit (mother tax). In particular, if there is a particularly wet period during flowering and fruit set, AND, the vegetative canopy is too vigorous and overwhelming, the environment under the canopy becomes difficult. Fungal pathogens thrive in the extremely humid environment under the canopy. And perhaps most important, honeybees have difficulty penetrating a dense canopy to get to the female flowers underneath. They tend to be a bit lazy and will settle for the male flowers at the top of the canopy. This leads to incomplete pollination and a lot of fruit with incomplete pollination will just fall off, often with grey mold all over it.

A couple of things to think about; Too much nitrogen fertilizer, whether its urea, ammonium nitrate or horse manure, will lead to excessive canopy growth, leading to the conditions I mentioned about. I helped Dr. John Swaider do a research project on nitrogen in pumpkins a number of years ago. We found that the optimum nitrogen rate is around 60-80 lb N/acre. I know a lot of pumpkin growers in Illinois use 120-180 lb N/acre. It can lead to the problems I mentioned above, and rarely results in increased yields.

Another thing to think about is fostering an environment for squash bees. These bees look a lot like juvenile bumblebees with black skin and yellow hair in stripes. But these bees are ground-dwelling and they like to nest in corn stubble. They can actually survive in conventional corn fields if neonicotinoid insecticides are not used. If you grow sweet corn, let the stubble dry down and create nesting opportunities for these bees. They are native and just need a little support to foster their success. We had them at our research farm and no one brought them in. They were local bees. They are excellent pollinators for all cucurbits, but especially squash and pumpkins. Do a search to learn more about them. In the Midwest, they should show up uninvited.

Another possibility is to make good use of organic mulches under the vines. They keep the female flowers off the soil, providing some limits to exposure to soil-borne fungi. The fruit will also be cleaner at harvest. Planting into rolled cover crops can serve this purpose.

William H. Shoemaker
Retired fruit and vegetable horticulturist
University of Illinois
wshoemak at illinois.edu

From: Market-farming [market-farming-bounces at lists.ibiblio.org] on behalf of Burke Farm [burkefarm at gmail.com]
Sent: Saturday, January 30, 2016 5:30 PM
To: market-farming at lists.ibiblio.org
Subject: [Market-farming] cucurbits

Hi all,

For several years, I've noticed that I can grow any cucurbit I want..
as long as it's not a c. maxima.

Any ideas what could be going on? Do they have higher / different
fertility needs, some kind of virus sensitivity, are first on the menu
for cucumber beetles / squash borers, or what?  Other growers in my
region seem to be able to grow at least some of them.

When I try to grow them, they do form a few fruit, but they are small,
rot on the vine before sizing up or ripening fully, and the vines die
early.  It's been several years since I've even given them a chance.

Lisa Burke
Farming Engineers
central IN z 5
clay loam soil
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