Protect Your Plants from Squash Vine Borer Damage

Author: Emma Grace Crumbley, Entomologist

Does your garden have zucchini, pumpkins, summer squash, or watermelon? If so, you need to know about squash vine borers. Squash vine borers (Melittia cucurbitae) are diurnal moths in the family Sesiidae, the group of moths best known for their clearwings and Hymenopteran mimicry (they sometimes look like wasps or bees). While adult squash vine borer moths do pollinate some flowers, their caterpillars can do more damage to your garden than the adults can make up for in pollination.

Squash Vine Borer caterpillars are small, white, and chunky with dark colored heads. They are sometimes mistaken for fly maggots given their stout bodies, but squash vine borers can grow up to an inch in length, much larger than a typical house fly larva. Squash vine borer caterpillars can also be mistaken for beetle grubs, however they do not curl up in the iconic “C” shape than grubs do when picked up.

As they prepare to pupate, a process that takes these moths months to complete before emerging as adults, squash vine borer caterpillars have to eat as much as they can to sustain themselves. For gardens, this often means munching on the stems and vines of wild and cultivated cucurbits, including melons, gourds, squashes, and cucumbers.

Adult moths are black and orange with two pairs of wings. When resting, they fold their wings in a way that may resemble an orange wasp resting on a plant. When they fly however, the fuzzy, black forewings and large, clear hindwings can be easily seen.

If you suspect you might have an infestation, check your plant carefully for the following signs of squash vine borers:

• Discoloration and wilting. This is often the first sign of an infestation and can inform you on which plants are being affected by these pests.
• Holes near the base of your plants. Caterpillars chew their way through plant vines and feed along the inside of stems, leaving behind holes for evidence. Holes will often be filled with frass (caterpillar droppings).
• Multiple caterpillars. To confirm beyond a doubt that you have squash vine borers infesting your plants, select a damaged plant and carefully cut along the vine with a sharp knife. Once open, look for those chunky, white caterpillars, and keep in mind that multiple caterpillars can infest the same plant.

Though squash vine borers can turn your garden from gourd-geous to gruesome, there are a few ways to prevent these pests and protect your plants from squash vine borer damage:

1. Plant cover crops to prevent adults from laying eggs near vines. Thes crops should be planted near the base of your cucurbits so they can exclude adult moths from laying their eggs on or close to vines.
2. Physically remove squash vine borer eggs and adults whenever possible. You can also attempt to remove the caterpillars from inside the vines directly, but keep in mind this may accidentally kill the plants in the process.
3. Contact your local extension agency to learn about biological and chemical control options you can use to reduce squash vine borers. Remember to always follow the labels and the law when using any organisms or insecticides around food sources, like cucurbits.

Borers Be Gone!

At Mosquito Squad Plus, we do more than just squash the pests in your yard. With treatment plans covering a variety of pests and tailored individually to each customers pest problem, our highly trained technicians provide excellent service to help protect your outdoor spaces from pests of all kinds. Call us today to learn more about our pest package programs and visit our website to find a Squad near you! Services vary by location.