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Squash Vine Borer

Adult squash vine borer moth.

COMMON NAME:  Squash Vine Borer

SCIENTIFIC NAME:  Order Lepidoptera, family Sesiidae, Melittia cucurbitae

SIZE:  Adult--1", larva--1" to 1 1/2"

IDENTIFICATION:  Adults are beautiful, narrow-winged black- and red-bodied moths that look like wasps. Eggs are brown, flat, oval, and singly laid on stems. Larvae are white caterpillars with brown heads.

BIOLOGY AND LIFE CYCLE:  Larvae tunnel into the base of vine stems, feed for four to six weeks, and cause the entire plant to wilt and die. They hibernate as larvae or pupae in cocoons about an inch deep in the soil. One or two generations a year.

Squash vine borer larva and associated damage on squash stem.

FEEDING HABITS:  Larvae (borers) enter the base of the stem in early summer, causing a greenish frass, and leading to wilting, and death. They will also feed on fruit of cucumbers, gourds, melons, pumpkins, and squash.

ECONOMIC IMPORTANCE:  Destruction of squash plants.

NATURAL CONTROL:  Plant more than just a few plants. Plant early and promote vigorous growth. Plant cucurbits with more solid stems, such as butternut and winter squash. Beneficial nematodes.

Squash vine borer damage.


Plant response to squash vine borer damage.

ORGANIC CONTROL:  Slit the stem and remove the borer. Pile soil over the damaged stalk. Some say injecting Bacillus thuringiensis or beneficial nematodes in the stalk with a syringe works. Both methods are a lot of trouble. Cover plants with floating row cover, but remove when the female flowers start to form. Spray plants with a Bt product when yellow flowers first bloom. Check the base of stems often to remove the reddish eggs before they hatch. Treat soil with beneficial nematodes.

My friend Bob Webster and his partner Roberta Churchin own a wonderful 100% organic nursery (Shades of Green) in San Antonio. Bob does an organic gardening talk show  there on KTSA. One of the most common questions we both get every year is how control squash vine borers. Here's his tip that seems to work very well. This is what I'm doing for squash borer prevention this spring - actually injecting Bt into the stems which are hollow, especially the yellow squash varieties, so it's easy to put about 5cc into each plant."

INSIGHT:  Squash vine borers tend to avoid big squash farms but destroy home gardens, so plant more plants.

Squash vine borer eggs from from a dead adult's body. ​Squash bugs eggs look almost identical but will be scattered on the stems near the ground rather than in tight clusters on the backs of leaves.

Tip from Listener:

Squash bugs (different than squash vine borers) - listener tip. 

Periodically, I would check the underside of the leaves, and if eggs are  found  I use masking tape, and lightly pressing against the eggs to get them to transfer from the leaf to the tape, then just fold the tape over and squeeze to mash the eggs, then throw in the trash. 

Trying to remove the eggs otherwise would damage the leaf. Masking tape is not that sticky and seemed perfectly suited to the task.
Then since eggs were evidence of the bugs'  presence, I would turn on the hose and flood the base of the plant.  The adults would climb up to get away from the water and I'd just pick them off with gloved hands and crush them.  Jeff Morrow, Arlington, TX

Another of my listeners called with a tip on controlling squash bugs and claims it works great. The technique is to put the plants in cages like those used for tomatoes. Growing the plants vertically rather than sprawled on the ground apparently keeps the bugs away. Give it a try and let us know if you have the same results. The most recent is the gardener who let us know that he ground up bay leaves and worked them into the soil before planting and had no squash bugs for the first time in many years. We all need to try this on squash vine borers. It might work on them as well.


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