Beating the Bugs
by VCE Agent Kirsten Conrad
The information here was originally published in a monthly column on pest control in Between the Rows – A Guide to Vegetable Gardening published by VCE in collaboration with MGNV.
Don’t miss Kirsten’s in depth online class:
What’s Eating My [Cucumbers, Tomatoes, Eggplant, Beans, Squash]? :
Insect Pest Management for the Vegetable Garden
Pests of Cucurbits (cantaloupes, cucumbers, squash, pumpkins, and watermelons)
Insect pests of the squash family are among the most hated by gardeners. Aphids – covered in April Vegetable Gardening on pests of legumes – are pests of plants in this family. Another two that are known troublemakers are the larvae of leaf miners, which eat their way between the layers of leaves, and pickleworms, which eat into flowers and buds. Likewise the piercing/sucking feeding of stink bugs and leafhoppers are known to do damage to this family of plants. However, the pests of squash, melons, and cucumbers that we get the most complaints about are squash bugs, squash vine borers and cucumber beetles.
Squash Vine Borers
The squash vine borer attacks all the members of this plant family: cucumber, cantaloupe, winter squash, pumpkin, gourd, summer squash, and watermelon, to name a few. The damage is caused by the larval stage of the moth as it bores into stems, which can cause the vine or entire plant to wilt and die. Adult moths emerge from winter hibernation when the Japanese stewartia and smoke tree are blooming. They lay eggs on the base of vines, and after hatching, the new larvae quickly bores into the stem where it will feed until it is full size and ready to exit the vine and pupate into an adult. The stem will often wilt and die if corrective action is not taken.
Cultural Controls: Plant cucurbits as late as possible to avoid this and other pests. Use a row cover from planting until first flower. For cucurbits with long running vines, place a single shovel full of soil over the vine about every 6 feet; this will aid in developing secondary roots. It is possible to carefully cut infested stems open to find and extract the larvae, and then cover the stem with soil to encourage re-growth. Tilling the soil may reduce the overwintering pupal life stage.
Organic Controls: Products like kaolin clay can be applied to stems to discourage the egg laying and boring, and registered insecticides are available to home gardeners. It’s important to treat as soon as the first damage is found and continue every 10 days for the rest of the growing season. Care should be taken to prevent damage to pollinating insects.
Varieties resistant to squash vine borers tend to have thin, tough stems. In addition, vining types are more resistant than bush types since the former can root along their nodes and survive moderate levels of borer damage. The most resistant varieties include butternuts and Green Striped Cushaw, followed by Dickenson pumpkin and Summer Crookneck. Other varieties reputed to have at least some resistance include acorn squash, Cucuzzi (also known as snake gourd), and Connecticut Field, Dickenson, and Small Summer pumpkins.
For more information on the squash vine borer see Squash Vine Borer by Theresa A. Dellinger and Eric Day, Department of Entomology, Virginia Tech.
Two types of cucumber beetles, both about 1/4 inch long, are commonly seen in Virginia gardens: striped cucumber beetle and spotted cucumber beetle. Both types attack many different cucurbit crops, including cucumber, cantaloupe, winter squash, pumpkin, gourd, summer squash, and watermelon. Cucumber beetles may also feed on beans, corn, peanuts, and potatoes.
These insects damage leaves, stems, and fruit. They can also transmit a disease called bacterial wilt.
Cultural controls: Cultural control can sometimes be achieved by planting pumpkins, squash, and cucumbers late in the season after about June 15. Row crop covers will exclude the beetles but need to be in place from planting until bloom. These row covers also can provide late frost protection and help with moisture retention. Rotating crops with nonhost plants is effective, and resistant varieties of cucumber and melons are available. In general, cucumber beetles prefer zucchini-type squash over others and don’t like burpless cucumbers, as well as other varieties. Blue Hubbard squash, Ashley, Chipper, Gemini, Piccadilly, Poinsett, and Stono cucumbers; Early Prolific, Scallop, Straightneck, and White Bush squash; and Galia, Passport, Pulsar, Rising Star, and Super Star melons are all reported to be resistant to cucumber beetles.
Chemical controls: Chemical control is sometimes recommended to prevent damage to young seedlings and disease transmission. Products listed for this use include carbaryl, imidacloprid, and permethrin. Organic/biological control products include azadirachtin, kaolin clay, neem oil, and pyrethrins.
For more information on cucumber beetles see Cucumber Beetles by Eric Day, Insect ID Lab Manager, Department of Entomology, Virginia Tech.
Squash bugs are often first identified by their coppery brown clusters of eggs. Newly hatched nymphs are green but turn to gray as they age, and the 1/2 to 3/4 inch adults are dark brown to black. Squash bugs can attack cucumbers but prefer squashes.
Feeding causes leaves to wilt and fruit to develop poorly and rot. Squash bug damage can be confused with bacterial wilt in cucumbers, which is transmitted by cucumber beetles.
Cultural Controls: Use row covers from planting until flowering at which time covers need to be removed to allow pollination. Reduce populations by scouting for and removing the clusters of golden eggs at the time of vine elongation. End of season cleanup of garden debris and weeds will reduce the number of overwintering adults. Squash bugs prefer yellow summer squash over zucchinis, squash over pumpkins, pumpkins over gourds, and gourds over melons. Resistant varieties include acorn squash, butternuts, Early Summer Crookneck, Green Striped Cushaw, Improved Green Hubbard, Spaghetti, Sweet Cheese, and zucchinis (except for the susceptible Cocozelle).
Chemical Controls: Recommended chemical control of squash bugs in home gardens include using permethrin, kaolin clay, insecticidal soap, and pyrethrins.
For more information on squash bugs, see Squash Bugs by: Rick Foster, Purdue University Extension.