If you’ve noticed your summer squash plants suddenly wilting, even in the cooler morning hours, you may have squash vine borer larvae feeding on your plants. The adult squash vine borer is the clearwing moth. It is about ½-inch long with metallic-green front wings and clear back wings. The abdomen is orange with black spots. Squash vine borer eggs are very small, flat and brown. The larvae resemble maggots with a whitish/cream colored one-inch long body and brown head.
Life Cycle
There is one generation of squash vine borer each year. From late June through early July the adult moths emerge from the ground and lay eggs. In about one week the eggs hatch and larvae begin feeding within the stems of squash plants. After eating for four to six weeks they pupate in the soil until the following summer.
Damage
Squash vine borers feed on summer and winter squash as well as pumpkins causing yellowing leaves and wilting. If you notice holes in the stems near the base of the plant look for a sawdust-type material that is moist and green/orange in color. This is evidence of borers.
Control
Treating plants with active larvae is difficult. It is best to monitor plants for the adult moths and treat before the larvae can infest the plants. Another suggestion is to plant a second crop of summer squash in early July so the crop will mature when the borers are pupating rather than when they are most active. Crop rotation is very important to prevent the spread of this pest due to how they overwinter in the soil. Once you know borer larvae are present you can slice open the stem to attempt to locate the borer(s) and manually remove them.
Insecticide applications need to begin when the squash vines begin to spread and reapplied every seven to 10 days through the end of June. Direct spray the crown of the plant and the base of runners. Chemicals that may be used for borers are permethrin (Eight Vegetable, Fruit & Flower Concentrate; Garden and Farm Insect Control; Lawn & Garden Insect Killer) or bifenthrin (Hi-Yield Bug Blaster II, Bug-B-Gon Insect Killer or Lawns & Gardens) applied as sprays or dusts. (Cynthia Domenghini)