Squash, Zucchini

On a recent visit to a farm I saw bright yellow leaves in a pumpkin field and wondered if this could be Cucurbit yellow vine decline that was first seen two years ago (fig. 1). Upon closer inspection of the plants it was found to be an old nemesis of pumpkins and squash - the squash vine borer. Borer moths lay eggs mostly at the base of pumpkin and squash plants starting in late June and going through the first few weeks of July. Eggs hatch and borers quickly move their way into the base of the pumpkin stem where they feed inside the stem (fig. 2) disrupting water and nutrient flow to the rest of the plant (fig. 3).

There have been problems in our vegetable fields with three pests, which include striped cucumber beetles, leafhoppers and twospotted spider mites. I think most of the problems we are having with these three comes from our mild winter as each has had an outbreak population after a mild winter sometime in the last 12 years.

Fruit and Vegetable News, Volume 12, Issue 4 (July 15, 2021)

Evaluation of fungicides for management of powdery mildew on squash, 2015

A County agent sent pictures of squash that were turning yellow and wilting (fig. 1). This was found to be Fusarium crown rot caused by the fungus Fusarium solani f. sp. cucurbitae with a little Anthracnose caused by Colletotrichum orbiculare mixed in with it. In the field, Fusarium crown rot is generally a problem in summer and winter squash, and some pumpkin cultivars, but most cucurbits have been found to be susceptible.

Striped cucumber beetles (Acalymma vittatum) (SCB) are the most important insect pests of muskmelon and cucumbers in our area. They overwinter as adults and emerge when temperatures reach 54–62°F at which time they begin searching for cucurbit hosts. Volatiles produced by the plant attracts SCB to cucurbits initially, then male SCBs produce an aggregation pheromone attracting more beetles. The beetles tend to mass on small plants where they eat, mate and defecate (fig 1).

I am seeing some plectosporium blight in a few pumpkin fields this year, not as bad as last year but still there. This disease will probably increase if we continue having frequent rains in some locations.