This are the looks of the squash vine borer — top from left, the insect's eggs on a squash stem, and exposed larva after a stem is sliced; and bottom from left, adult squash vine borer moth, larva close-up, and the collapse of a squash plant after vine borer infestation.

Second of two articles on insect pestsIf you've had a squash plant suddenly wilt and die, it was most likely infested by the squash vine borer.This insect, Melittia cucurbitae, can destroy squash, zucchini, pumpkins and less frequently cucumbers and melons. It causes the affected plant to collapse, seemingly overnight.The adult squash vine borer is often mistaken for a wasp with its metallic green front wings, transparent rear wings and orange body with black markings. It is actually a clearwinged moth that is active during the day.Squash vine borers overwinter as pupae or cocoons in the soil. In mid to late June, the adult moths emerge and begin laying eggs on squash plant stems near the soil surface.As soon as the eggs hatch, the tiny worms tunnel through the stem to feed, blocking the flow of water and nutrients, causing plant wilt and eventual death.By August or early September, they are ready to burrow into the soil and overwinter as cocoons, starting their destructive cycle over again.Once the borer larva enters the squash stem, little can be done to kill it, so it is important to take preventive measures.Till the ground after harvest and again in the spring to kill many overwintering cocoons.Destroy infested vines during the growing season and after harvest. This can prevent larvae remaining on the plant from completing their development.Practice crop rotation when planting squash.Plant vine crops that are not as attractive to the squash vine borer such as butternut squash, cucumbers and melons. Hollow stemmed plants such as pumpkins, zucchini and Hubbard squash are very susceptible.Plant in early July so the plants will mature after the adult borers have finished egg laying.

Cover the stems with strips of nylon pantyhose or aluminum foil to prevent the adult from laying eggs.Cover plants with a floating row cover. Securely anchor the row cover to the ground so that the moths cannot enter underneath. Remove the covers once the plant begins to flower to allow pollination.Monitor your plants beginning the last week of June for signs of the adult moth activity. They are rather conspicuous when flying and make a noticeable buzzing sound.Because the moths are attracted to yellow, place yellow bowls filled with soapy water in your garden to trap them. If you do find them in your traps, you know it is time to take action.Check your plants for flat, brown, singly laid eggs. These eggs typically hatch in 7 to 10 days. You can use insecticide, but timing is key, as it must be applied just before the eggs hatch.To protect the plants, spray along the stems and near the base. Among organic pesticides, those containing neem, spinosad or pyrethrin as the active ingredient are the most effective. Follow the instructions on all insecticide labels carefully when using.Once the caterpillar has bored into the stem and begins to feed, it pushes sawdust-like fecal matter outside the stem.If you notice this, you have only one option left: split the vine lengthwise with a sharp knife and remove any borer larvae you find with the tip of the knife.Pack moist soil over the cut area and keep watered. New roots may grow and the plant may survive.If you have questions regarding squash borer control or other gardening issues, contact the Master Gardener Greenline at 724-287-4761, Ext. 229.

Mary Reefer has been a Master Gardener since 2012. She lives on a farm with her husband in Mount Chestnut. She enjoys both vegetable and flower gardens. She is a Greenline volunteer answering a variety of horticultural questions. In her spare time she is studying to be a certified botanical illustrator at Phipps Conservatory.