Cucurbits

I have been seeing and receiving a few samples of yellowing (chlorosis) around the margins of cantaloupe leaves (Fig. 1). The marginal chlorosis observed in figure one would indicate salt burn, which is a noninfectious problem that mostly affects cantaloupes. This yellowing at the leaf margin is likely the result of guttation, which is how plants exude water at the margin of the leaf.

Starting to see some watermelon, cucumber and other cucurbit crops that are looking a bit pale green or even yellow (fig. 1). Sometimes the plants have brown speckles or spots on them that may look like a foliar disease has started (fig. 2).

There have been several reports of odd looking damage to watermelon transplants being grown in greenhouses these past couple of weeks. The damage does not appear to be cold damage per se, but more of a strange environmental/weather one. Watermelon transplants, along with some other vegetables, began showing dark pitted lesions on their cotyledons (fig. 1).

I am seeing and getting reports of virus infected squash, pumpkin and cucumber fields, so I thought I’d go over some information about viruses. Several aphid species are responsible for transmission of the most common virusesin cucurbits. Although some cucumber beetles have been shown to vector some viruses (such as Cucumber mosaic virus) their success rate under field conditions makes them a minor contributor to most virus infection problems.

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.

IPM Threshold Guide for Vegetable Crops

Managing Downy Mildew of Cucurbits