Squash bug control

Squash plants are target for bugs, disease

Bill Sevier: Ask a Master Gardener

Saturday, April 23, 2016

Q: I lost my squash last year to squash bugs. How can I prevent them from destroying my plants this year? Troy, Tulsa

A: Squash is popular in the vegetable garden, and insects and disease represent the major challenge to successful production of fruit.

Three main insects are problems for these vegetables — squash bugs, squash vine borers and cucumber beetles. They are also problems to varying degrees for other vegetables in the cucurbit family (squash, cucumbers, melons, cantaloupe and pumpkins).

Squash vine borers attack the vines at their base; squash bugs suck sap from leaves causing them to develop yellow to brown spots and often wilt, especially in young plants. Cucumber beetles do little feeding damage but can infect the plants with a bacterial wilt disease.

OSU has been involved with studies to investigate control methods. One study involved floating row covers to exclude squash bugs. Row covers are thin, lightweight synthetic material allowing sun and rain to enter but keeping insects out. Covers were put in place at time of planting and removed at various intervals after 50 percent of the plants had female blossoms (ones with tiny fruit at their base). Since squash must be pollinated by insects, the covers were removed to allow bees and other pollinators to visit the blossoms.

The study showed row covers did reduce, but not eliminate, the need for insecticides. The covers also protected plants from hail and winds but delayed early harvest. However, later harvest was extended. A downside was that covers were more expensive and labor intensive.

Another OSU study looked at companion planting as an attempt to control squash bugs. The herbs feverfew and white yarrow were grown with the squash, and no benefit was found after 3 years.

There are other ways to help with the insect control such as planting more resistant varieties. Butternut, Royal Acorn and Sweet Cheese have shown some resistance. Also, if you have only a few plants, hand removal of bugs and eggs is effective. The eggs are diamond shaped, yellowish to bronze and are easily seen in clusters on the underside of leaves.

Another control strategy for some gardeners is to place small boards next to the vines. Adult bugs will hide under these at night where they may be found during the day and destroyed.

Other cultural controls include cleaning up all insect-containing debris from the garden at the end of the growing season. Tilling the garden in the fall will also help by exposing overwintering insects to the cold in winter. Some gardeners also find it helpful to plant a second squash crop in mid-summer, after the major insect activity in spring and early summer has passed.

Lastly, organic and conventional insecticides are available for help with control. You may find these listed online by searching for squash bugs at the Oklahoma State Horticulture website.

Garden tips

Lace bugs, aphids, spider mites, bagworms, etc. can start popping up in the landscape and garden later this month. Keep a close eye on all plants and use mechanical, cultural, and biological control options before going to insecticides. If an insecticide is needed, use one of the organic ones such as horticultural soap, Neem oil or pyrethrin.

Remove any winter-damaged branches or plants that have not begun to grow. Prune spring-flowering plants as soon as they are finished blooming.

Proper watering of newly planted trees and shrubs often means the difference between success and replacement.