Eastern NY Vegetable IPM Program

The purpose of the trial was for growers to view the new Powdery Mildew tolerant varieties. There are now over a dozen PM tolerant varieties. The new varieties are also in a selection of sizes so growers can us a PM tolerant variety for all their marketing needs.

If I can do this, you can too!

WHY DID MY PUMKINS NOT SET FRUIT THIS SUMMER?
H. C. Wien, Dept. of Horticulture, Cornell University

It’s early fall, and the pumpkin plants are still a mass of vines, with only small fruits that may have problems getting ripe. Assuming that the crop was planted in early to mid-June in Upstate NY, there should have been plenty of warm weather in 2006 to have pumpkin fruit close to maturity by this time. So what went wrong?

It is quite possible that the warm conditions were too much of a good thing. Our research in the 1990’s indicated that many pumpkin varieties fail to develop normal female flowers when daytime temperatures in the 90’s are encountered at about the time of flowering. The female flower buds turn yellow and fall off, instead of growing normally and opening, so that they can be pollinated by bees. Weather records for the Ithaca area show that there were 9 days in July, and the first three days of August, in which temperatures were significantly higher than normal. Conditions could have been warm enough to prevent normal female flower development during that time. That means that normal flowering would not have resumed until mid-August, and the small fruits now visible on the vines were set during that cooler weather.

Another factor which can complicate the picture is the amount of light received by the individual pumpkin plant. If the plants were shading each other, due to dense planting in the field, or excessive fertility, in the ample moisture that occurred during our growing season this year, plant growth could have become excessive, so that the plants were competing for light with each other. Under such conditions, the pumpkin plant again has difficulty developing normal female flowers, and the result is delayed and sporadic set. Poor weed control, especially of tall weeds like velvetleaf, can make this situation worse.

What can be done about this situation? For this season’s crop, we can only hope that the fall will be mild and long, so that the delayed crop can come to maturity. To avoid the situation in future years, choose varieties that are less viny, and which have compact vines and set fruit early. We have not done a systematic screen for heat tolerance among the many pumpkin varieties, so that information is still lacking. To avoid the mutual shading, using wider spacing, keeping weeds under control, and planting only in fields of moderate fertility are recommended practices.

There are still a lot of pumpkins in the field. At this point, there is a lot of powdery mildew knocking down the vines. Once the pumpkins have turned yellow, it is a good idea to cut the stem. If the stem is not cut, the powdery mildew will weaken the stem. As we all know, a pumpkin without a stem is worth less. People want a strong stem to carry it out of the field with.

If you are not doing pick your own, it is a good idea to get the pumpkins out of the field. With all the rain, standing water will bring out phytophthora and distroy the pumpkins. Also, squash bugs and cucumber beetles build up and feed on mature fruit so damage can come that way too. At the very least, gather up the pumpkins on high, dry ground away from where the diseases and insects can get to them.