Protect Squash from Vine Borers

Each year I receive several calls from home gardeners telling me that their squash vines just wilted overnight. Two years ago I had a call from the Dalton's at Pumpkin Hollow and they too were experiencing wilting in their pumpkins. Both of these situations were caused by the larvae stage of the squash vine borer. According to Dr. John Hopkins, Assistant Professor and Extension Entomologist with the University of Arkansas Division of Agriculture, Cooperative Extension Service, squash vine borers in Arkansas are one of the most damaging and most common pests of squash, especially in home gardens. Plant types affected include Hubbard squash, gourds, pumpkins, zucchini, acorn squash, and yellow squash. Butternut squash is less susceptible that other squashes and cucumbers and melons are usually not attacked.

The adult of the squash vine borer is a clear winged moth with metallic greenish-black scales on the front wings. The hind wings are transparent and can often be mistaken for a wasp. The adult is approximately one inch long and the abdomen is ringed with orange and black. Female moths lay their eggs which are small (1/25 inch) somewhat flattened brownish at or near the base of the plant close to the ground. They usually lay their eggs in late May or early June. Young vine borers hatch in about a week and tunnel into the stem. Larvae feed for about four weeks until they are grown. The stems and entire plant will usually wilt and die. Essentially the borer has eaten up the inside of the stem resulting in death to the plant. The borers then leave the plant and burrow into the soil and form a cocoon. Two or three weeks later the adults emerge, giving rise to a second generation of squash borers usually in early August.

To get ahead of these pesky pests there are a few things you can do. There are several non chemical control measures that can be utilized to minimize the impact of squash vine borers in the home garden. First you should plant borer tolerant cultivars. Second, you can cover emerging plants with floating row covers to provide early protection on young plants. When blooming begins, the covers should be removed. You can also wrap the stem and base of the plant with something like pantyhose to prevent the laying of eggs by adults. When utilizing chemical control measures to manage squash vine borer, timing is critical. The key to managing this pest is with insecticides is controlling the borers before they enter the stem. Once inside the vine, insecticidal control is ineffective. Beginning in mid May, plants should be monitored for feeding signs and borer's frass at entrance holes in the stems. Insecticide applications should be targeted to control newly hatching larvae and should be initiated when early signs of larval feeding occur or when vines begin to run. Adequate control may require multiple applications on a five to seven day interval as directed by the label of the insecticide you use. Spraying preventively is a good idea before signs of borers are seen. Thorough coverage is necessary on the stem and lower part of the plant.

The following insecticides are examples of materials that are available to homeowners and will provide adequate control of squash vine borers if applied properly: insecticides with the active ingredient bifenthrin (Ortho Bug-B-Gon MAX Lawn & Garden Insect Killer Concentrate 0.3%). Insecticides with the active ingredient esfenvalenerate (Ortho Bug-B-Gon Multi-Purpose Insect Killer 0.0033%), spinosad (Ferti-lome's Borer, Bagworm, Leafminer & Tent Caterpillar Spray 0.5%, or Monterey Garden Insect Spray 0.5%). Also products with the active ingredient permethrin will work as well as the product Pyrellin. All chemical information is given with the understanding that no endorsement of named products is intended nor is criticism implied of other similar products not mentioned. Remember to always read the label before using any pesticide and follow the directions on the label.

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