Gardeners' Dirt: Squash borers - nemesis to growing squash

By Gerald Bludau - Victoria County Master Gardener Edited by Charla Borchers
Feb. 28, 2013 at midnight
Updated Feb. 27, 2013 at 8:28 p.m.

The squash borer is a clear-wing moth with metallic greenish-black coloring and black and red-orange markings over its abdomen.  For its small size of 1-inch wing expanse, it can develop into a borer that can completely destroy a squash plant.

The squash borer is a clear-wing moth with metallic greenish-black coloring and black and red-orange markings over its abdomen. For its small size of 1-inch wing expanse, it can develop into a borer that can completely destroy a squash plant.

With winter coming to an end, it is time to begin preparing for your spring garden. One of the most popular garden vegetables in this area is squash, a member of the cucurbit family, which also includes cucumbers, cantaloupe and watermelons.

Growing squash can be fun, offer an abundance of homegrown bounty for friends, family and neighbors and, in most cases, be grown successfully; however, there is one nemesis that bothers most home gardeners: the squash borer.

Diurnal (daytime activity) moth

The squash borer (Melittia cucurbitae) is a diurnal (daytime activity) species of the sesiid, or clear-wing moth. It is known as clear wing because the hind wings are almost without scales. It is 11/2 inches in wing expanse, has a metallic greenish-black color and black and orange markings over much of the abdomen. This moth is often mistaken for a bee or wasp.

It lays its eggs on the underside of the squash leaf, and the developing borers feed inside the stalk, eventually killing the leaf. They soon migrate to the main stem and, if aggressive enough, can kill the entire plant. Sudden wilting of a vine and sawdust-like insect waste coming from holes in the stem are evidence of attack.

They seem to cause the most trouble where only a few plants are grown in gardens and rarely attack other members of the cucurbit family, namely cucumbers and melons. Some varieties of squash are more susceptible than others.

Pesticide is generally ineffective once the larva is in the plant. This is a very difficult pest to control, especially if it is not identified until the damage is done.

Natural control

As a gardener, you can have some success by trying natural routine control. This may include:

Destruction of vines after harvest to destroy any remaining larva in stems

Early spring plowing to destroy cocoons that may have overwintered in decaying plants

Rotating similar crops to different areas of the garden from one year to the next

Covering roots of the plant to encourage secondary rooting to support plants with stem damage

Destroying moths in early morning or late evening when they are resting on the underside of the leaf

Picking off the eggs before they hatch

In researching this article, I found that this is a very difficult pest to control. One may want to stagger your squash planting, so if you lose some of the harvest, you will have others coming into production.

Applied chemical control

In my own experience, I have had some success by close observation of the young plants. When I see the first bloom, I know the moth will soon be around to feed on the nectar of this bloom. Once I observe the first bloom, I dust each stalk of the plant with Sevin dust (carbaryl) or Malathion at the base of the plant to as high as 8-10 inches. This can generally kill the moth before the eggs are laid. I cannot take credit for this method of control, as I learned this from our former county agent, and it is fairly successful.

I have another suggestion for control - and this is for people who have a lot of time on their hands. Try mixing some liquid Bacillus thuringiensis, according to the labeling instructions. Put this in a syringe and inject each stalk with this mixture. It will probably kill the larva.

A combination of the natural control methods and chemical control if needed is the best course of action to manage most insect problems. Prevent the problem to the best of your ability through good cultural practices and use pesticides if and when a problem arises.

Resort to store-bought

When these methods fail and you really love squash, there is only one other thing you can do. Try the produce department of the area grocer.

Squash is a relatively easy plant to grow for most gardeners and has the ability to provide a continuous supply of the tasty, garden fresh dish for several weeks - or year-round, if canned.

If you are successful at raising squash - and most of us will be - try the excellent recipe included with this article.

The Gardeners' Dirt is written by members of the Victoria County Master Gardener Association, an educational outreach of Texas AgriLife Extension - Victoria County. Mail your questions in care of the Advocate, P.O. Box 1518, Victoria, TX 77901; email or comment on this column at



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