Cucurbit yellow vines disease affects squash, pumpkins and other members of the cucurbit family, causing the foliage of the plants to yellow, wilt and eventually collapse. County Extension Agent, Randy Drinkard reports in the Lagrange News on August 16 that wet weather – like that experienced in Maine this year – creates a breeding ground for many diseases effecting cucurbits. Yellow vine disease is no exception. It occurs as the result of an infestation of squash bugs (Anasa tristis).
“Got Pests?” a featured section on the Maine Government site, explains that when squash bugs feed on cucurbits, they inject bacteria into the plant. As a result, the plant foliage wilts, turns yellow and eventually dies.
Keeping squash bugs under control is the best preventative measure for yellow vine disease.
Squash bugs lay rows of tan, brown or reddish-brown eggs on the undersides of leaves or along the stems of cucurbits. They prefer pumpkin and squash, but may infest cucumbers and other cucurbits, such as melons and gourds.
The larvae and nymphs of the squash bug typically do the most damage as they devour the foliage. Larvae are soft-bodied and appear gray or silver, while the growing nymphs look like fat, gray spiders with long black legs.
Handpicking the larvae and nymphs is difficult, but can be accomplished by holding a bag under the affected leaves and cutting the leaf from the plant. Dropping the leaf into the bag and disposing of the plant material away from the garden slows the spread of the disease.
Treating the eggs by removing them with a cotton swab dipped in rubbing alcohol is effective in small gardens. Otherwise, both carbaryl, sold under the brand name Sevin, and perethrin, the active ingredient in Ambush, are reported to be effective in controlling squash bugs.