Squash Vine Borer in the Garden

The squash vine borer is a clear-winged moth that lays its eggs on squash and pumpkin plants. The larva tunnels into the stem and crown of the plant and eats the pith inside. The center carries water and nutrients to the plant, so the leaves turn yellow and wilt, and the plant dies when the center is eaten.

Description of the Squash Vine Borer

Adult squash vine borer moths are about half an inch long. They are black with an orange abdomen covered in black spots or stripes, mimicking a wasp. The front wings are metallic green, and the back wings are transparent.

The eggs are flat and brown. They are tiny, so they are hard to see. The larva is creamy white with a black head.

Life Cycle of a Squash Vine Borer

Squash vine borers overwinter as pupae. In the spring, they emerge from the ground and lay their eggs one at a time at the base of squash vines. After about a week, depending on temperature, the eggs hatch, and the larvae bore into the vine stems, blocking the flow of water to the plant. After feeding for four to six weeks, the larvae bore out and dig two inches into the ground to pupate. There is one generation of squash vine borers in cooler areas a year. In warm areas, such as Texas, there are two generations of squash vine borers a year.

Symptoms of Squash Vine Borer

A squash vine borer’s entry hole into a squash vine is very small. Usually, the first sign of a problem is when leaves turn yellow and wilt. Eventually, that runner or vine will die.

Control of the Squash Vine Borer

Squash vine borers are difficult to control. Therefore, you will need to integrate non-chemical and chemical control measures to manage the squash vine borers in your garden.

Non-Chemical Controls

• Remove dead and dyin Don’th vines and put them in the trash if you leave them, that allows the larva to pupate and come back next season.
• Rotate your cucurbit crops. Don’t plant squash or cucumbers in the same place where you grew them last year.
• After the garden is finished in the fall, till the earth around the squash plants with a spade. Squash vine borers dig two inches into the soil to pupate. If you turn the world to bring them to the surface, hungry birds will eat them.
• If you have well-tilled your garden or have never grown squash there, you can use a floating row cover over your squash vines to keep the moths from laying their eggs. You will need to bury the edges of the row cover to keep the moths out. When the vines start floweri ‘you wi’l either have to remove the row covers or hand-pollinate the flowers.
• These types of squash are less attractive to the squash vine borer: ‘Tatume’ (Calabacita) squash, white bush scallop, acorn squash, summer crookneck, Dickinson pumpkin, green-striped cushaw, butternut squash, and zucchetta squash.
• Carefully slit the base of the vine with squash borer larva in them and remove the larva. There may be more than one larva in a vine.
• Stagger your squash planting so that the newer ones will start producing as the older vines die.

Chemical Controls

• Bacillus thuringiensis (Bt) is a pathogen that kills caterpillars like the squash vine borer. You can spray it around the base of the vine, so it gets on the caterpillar as it bores into the vine. Some people inject the Bt into the vine, which is time-consuming. Bt is allowed in organic gardening.
• Use Spinosad, another insect toxin that is allowed in organic gardening. Spray this weekly on and around the base of the squash plant. Spray in the evening as it is toxic to bees until it dries.
• Entomopathogenic nematodes prey on a variety of insects. Some research has shown they will kill squash vine borers, while other research has not. You can purchase these from online garden supply companies.
• Conventional insecticides applied to the stems and ground around squash can be effective. Make sure the insecticide you choose is allowed to be used on vegetables and that you apply it on the branches, not the leaves, flowers, or fruit. Doing so this way will minimize the effect on bees and other pollinators.

When to Use Chemical Controls

Use chemical controls in the evening to minimize their threat to bees and other pollinators. Start using them when you first see the moths flying or notice the caterpillars. Then, continue weekly until the season ends. Use the chemical on the vines, not on the leaves, flowers, or fruit.

Squash vine borers are one of those pests that you manage, not eliminate. Use chemical and non-chemical controls to maximize your squash yield and minimize your losses to the squash vine borer.