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Molly Lyles, Carlton, Christopher E.
The squash vine borer (Eichlinia cucurbitae) is a wide-spread clearwing moth (family Sesiidae) pest of many cucurbits in Louisiana that can cause significant damage if left uncontrolled. The eggs are brown, flattened, ovoid and about 1 mm long. The plump, hairless caterpillars are grub or maggot-like in body form, white or cream colored, with three pairs of small legs and five pairs of leg-like prolegs along the abdomen. The body is obviously segmented, and the head is dark brown. The first body segment possesses a pair of diagonal brown lines. Newly hatched larvae are around 2 mm long and grow to 25 mm or slightly more when mature.
Adult moths are active during the day. Their bodies are about 13 mm long, with dark gray heads and wings. The abdomen is orange with black dots down the middle, except for the second segment, which is dark olive green. The legs possess long, bright orange fringes of hair. At rest, the wings are held over the body. In flight, the adults resemble and can be mistaken for brightly colored wasps.
Six species of cucurbit boring members of Eichlinia occur in North America, and several are similar in appearance to the squash vine borer. The only member of the genus confirmed in Louisiana is E. cucurbitae, but the western squash vine borer (E. calabaza) occurs as far east as central Texas and scattered records within Louisiana are posted online. These records require confirmation via specimen collections and vouchers. The second abdominal segment of the western species has some orange mixed with olive green, while the second segment of the eastern species is solid olive in color.
Squash vine borers go through complete metamorphosis with egg, larval, pupal and adult stages. Adults overwinter as pupae in the soil from the year prior. They emerge when soil temperature reaches around 60 F. They mate and begin laying eggs shortly afterward. Adults live for three to five days. Eggs are laid singly or in small groups just above the soil surface on the base of stems of plants in the family Curcurbitae (squash, gourds, cucumbers, melons and pumpkins). Eight to 10 days later the larvae hatch, bore into the stem or vine runners and begin feeding. Larvae feed for four to six weeks, exit the stem and burrow into the soil about 1 inch to 6 inches deep, where they pupate in a flimsy cocoon. They overwinter in soil in the pupal stage and emerge the following spring as adults, with one generation per year in northern areas and two in the south. Squash vine borer occurs throughout eastern United States, as far west as Texas and into southeastern Canada.
Once a plant is infested with larvae, little can be done to save the plant. Larvae bore through the stems, leaving sawdust-like frass at the base of the stem or along the vine where they entered. Vascular system feeding damage causes girdling of the plants, leading to wilt and death.
Squash vine borers are a serious pest for many cucurbit crops in Louisiana and make some varieties (e.g., yellow crookneck and Blue Hubbard) especially difficult to grow. Early detection and prevention are essential. Smaller plantings of susceptible cucurbits often suffer more damage than larger plantings because eggs are concentrated on fewer plants. Varieties such as butternut squash, cucumbers and most melons are typically not attacked.
Infected plants severely wilt during the day and strong winds may cause the plant to break from the base of the plant. Vining cultivars (e.g., butternut and spaghetti squash) produce roots at the leaf nodes, which can help supply water and nutrients and stabilize the plant even if the borers have infected the main stalk.
Monitoring is crucial to detect early adult moth activity. Adults are active during the day and can be trapped using yellow containers filled with water and a drop of dish soap. Check these traps daily for trapped adults. Pheromone traps can be used to attract male squash vine borers and help monitor their presence. Not all males will be captured. Thus, this serves as an indicator that adult females are laying eggs and that preventative action should be taken.
To locate infected plants, make regular inspections of the base of plants for eggs or frass (sawdust like fecal material) around larval entry holes.
Crop rotation is important to reduce insect and disease pressure. Since the squash vine borer overwinters in the soil, avoid planting susceptible crops in the same location year after year. Planting early can also help because smaller plants are more susceptible to damage. Starting plants early and transplanting to the garden when weather permits may allow a crop to be produced before plants become infested.
Trap cropping can help manage squash vine borers by luring them away from the main crop area. The trap crop should be a few weeks older than the main crop to attract the pest. To trap crop, transplant 2-week-old Blue Hubbard squash at the same time the main cucurbit crop is initially planted. Once pests are detected on the trap crop, apply insecticide to the roots. Some growers plant Blue Hubbard in pots treated with systemic insecticides to draw pests away from the main crop. Be sure to note edibility restrictions described on labels if insecticides are used on trap crops.
If an infestation is detected early, borers can sometimes be removed manually. Cut a vertical slit in the infected stem with a sharp knife to locate and remove larvae. After removal, cover the cut section of the stem with moist soil to encourage new root growth. This method is more feasible for home gardeners with a smaller crop, and success may be mixed.
Physical barriers can prevent adult moths from laying eggs. Floating row covers or insect netting can be used to protect young plants. Be sure to secure the edges of the cover to prevent moths from entering. Remove covers once plants begin to flower to allow pollination. If the cucurbits were planted in the same location as the previous year, this method may not work due to adults emerging under the row cover.
Tilling the soil after harvest and before planting in spring can help reduce overwintering pupae in the soil. Tilling the soil to a depth of 1 inch to 2 inches can expose pupae to predators and freezing temperatures, thus decreasing the population in the following year.
Insecticide treatments should begin when vines start to run or when the first signs of vine borers are observed. Refer to the Louisiana Insect Pest Management Guide for current insecticide recommendations. Always follow label instructions when applying insecticides, use approved products for the insect, and cropping system. Pheromone traps can help determine the length of time insecticides need to be sprayed. The focal area for insecticide application should be the base of the plant and applied based on label instructions when adults are active.
Contact Us: For advice about pest identification or diagnosis, contact the LSU AgCenter Department of Entomology. Reach the department through the Contact Us webpage.
P4017
9/16/25
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Squash vine borer adult in flight (Kepler1299, Wikipedia, Creatives Commons 4.0).
Squash vine borer larva in zucchini squash (Massive99, Wikipedia, Creative Commons 1.0).
Artistic representation of squash vine borer life history (Mary Foley Benson, U.S. Department of Agriculture, Smithsonian Institution, Department of Entomology, Bugwood.org).
