Squash Vine Borer

How to Prevent Squash Vine Borers

As with most pests, prevention is key. 

• Sometimes, the best solution is to start your squash as early as possible. This way, plants will be strong enough to withstand any mid-summer attacks and you may even be harvesting before squash vine borers become active. If you plant early, you may need to be prepared to cover your plants in case of late frost.
• Do not plant squash in the same area two years in a row. Squash vine borers overwinter in cocoons in the soil. Also, clean up and dispose of ALL plant debris in the fall.
• As soon as the squash plants are finished for the season, dispose of them. Till the soil in the fall and spring to get rid of overwintering pupae.
• Physical barriers can be an effective means of keeping squash vine borers at bay:
  • Cover the plants’ stems with a barrier, such as strips of nylon stockings or aluminum foil, to prevent egg laying. 
  • Before flowers appear on the plants, use row covers to keep squash vine borers away. The covers will need to be removed for pollinators, eventually. This will not only give you a head start over pests, but protect your plants from strong heat and frost.
• Adding parasitic wasps to your garden prior to the vine borer’s egg stage can be helpful, as these wasps are the borers’ natural enemy.
• If you give up on zucchini, which is susceptable to vine borers, try growing a squash that’s more resistant. Butternut squash and Cucuzzi (Lagenaria siceraria)—also known as the snake gourd—tend to be resistant to squash vine borer attacks.
• Plant extra squash for the pests! This pest is around for only 6 to 8 weeks and can only eat so much (or so we think!), so making sure you have plenty of plants to spare can help you avoid a total loss for the season.

How to Get Rid of Squash Vine Borers

If you’re already seeing signs of squash vine borers, use these methods to get rid of them or at least minimize their damage to your crops.

• If you catch them VERY early, you can manually remove the squash vine borer. Locate the entry point of the larvae, then slit the stem lengthwise with a fine, sharp knife to remove the larva by hand. One plant can house several larvae. Carefully remove the larvae without doing more damage to the plant. After removal, cover the slit stem section with moist soil above the point of injury to promote formation of secondary roots. Also, extra rich soil near the vines helps rerooting.
• If you can find the entrance holes and “sawdust,” try inserting a wire and thread it through the stem for some distance to kill the larvae inside.
• Sprinkle diatomaceous earth around the stalks when the squash vines are small or the threat of squash vine borers is high (early to mid-summer). Reapply after rain. Also, build up the soil around the vines. Or, sprinkle black pepper around the plants as a defense.
• If possible, catch and destroy the moths at twilight or in early morning when they are resting on the upper leaves of the plants.
• There are insecticides that work, too, but timing is critical; they are only truly effective when applied at the time when eggs are hatching.
  • The bacteria Bacillus thuringiensis v. kustaki (“Bt”) is a natural insecticide that can be injected into and applied to the squash stems.
  • Insecticides containing the ingredients carbaryl (Sevin) or permethrin will work on squash vine borers, too. Always be sure to read labels and warnings carefully before application of any insecticide.
  • Consult your local cooperative extension service for advice on appropriate chemical controls. 
• Trap the adult orange moths with yellow sticky traps and yellow-colored bowls of soapy water.
• A trap crop of very early-planted Hubbard squash can be used to alleviate pest pressure on other squash.
• An old folk remedy from The 1963 Old Farmer’s Almanac says that wood ashes were effective against the squash vine borer.

Learn about another main squash and zucchini predator: the squash bug.

Do you have any tips for controlling these pests? Let us know in the comments below!