Squash vine borer (SVB)Melittia cucurbitae
A common clearwing moth that flies during the day, it has an appearance of a wasp that can hover over flowers and plants, The moth’s range is mainly east of the Rocky Mountains from Canada to South America, cucurbit crops are the SVB target which includes the C. maxima , C. Pepo and C. moschata.The C. maxima varieties are the favorite and most attacked crop, for some reason the moth feeds heavily on small gardens and farm plots but leave large commercial areas alone or with much less damage.
The adult SVB is approx ½” long with a wingspan of 1½” the front wings have a green metallic appearance while the back wings are clear, and the abdomen is orange with black dots, The borer larva, has a fat, white or cream-colored body and brown head, fisherman may compare it to a wax worm; it can grow to about an inch long.After mating the male dies in 2 -3 days and the female dies 2-3 days after laying egg.
The female lays up to 200 eggs one at a time, usually at the base of plants and vine joints but all parts of the plant will be targeted, eggs are 1/25” long, brown, flat and oval shaped and hatch about 2 weeks after being laid.
When eggs hatch the larvae immediately chew into the plant living in the center hollow area where they feed 2 to 4 weeks destroying the plant circulatory system and causing rot to set in.many times you don’t know you have an SVB problem in tell you see the Frass(insect excrement) that the larvae leave their holes. It looks similar to fine wet sawdust.
After approx one month they drop into the soil where they lay as pupae in shiny smooth cocoons 1 to 6 “ below the surface of the soil. Most areas have one generation per year where they emerge from the ground late may/June lay around 200 eggs which hatch, eat, then return to the soil waiting for another spring to arrive.Lower states may have two overlapping generations and the North may have a second generation but they usually don’t develop fast enough to survive through winter.You can find cocoons in your soil during tilling and cultivation
Wilting of vines or the entire plant will be seen, soft and oozing vines are signs of rot from their feeding. The stump will show sign of frass and can be heavily damaged and rot completely off, vines will wilt from the damaged area to the tip from lack of water and nutrients.
Bacterial wilt or Fusarium wilt looks similar but the sign of frass will indicate SVB
Nonchemical control is limited, manually destroying the eggs is one method keeping an eye on the garden for signs of adult SVB which will indicate the start of mating. Low flying with a buzzing sound they can be seen hovering over plants, early in the morning and late evenings adults may be found resting on top of leaves.
Setting up yellow traps can help you know when SVB are visiting your garden, many types of traps are available some have attractants and poisons.
Once frass is found splitting the vine with a knife and extracting the larvae is another option several of them can come from one location, once you find them in one spot you can almost be guaranteed that there are more.The use of a thin wire shoved through entrance holes may kill and remove larvae, adding a small hook at the end will help fish them out.
Apply diatomaceous earth on the soil around young plants may kill adults and larvae, making sure you reapply after rains.Tilling after temperatures have dropped dramatically can disrupt adults in cocoons lowering the numbers that survive the winter. Row covers will work but only if you haven’t had SVB the previous year, in your garden, otherwise you will trap them under the cover with your plant.
Planting an early sacrificial crop of Hubbard squash around your property can draw in the adults then you can kill them in the manner of your choice.
Chemicals are by far the best method to control SVB
Follow directions and your state and local laws when using insecticides, you may want to contact your local cooperative extension office to obtain a private applicator’s pesticide license they will teach you the proper application of chemicals and how to handle them safely.
Hands down the most effective control is the active ingredient Imidacloprid found in products like Merit or Adonis 75 wsp, the price can vary greatly so shop around for generics.This product labeled for some trees and ornamentals is a systemic product, when drenched into the soil it’s absorbed by the plant and travels through all living tissue. Insects feeding or chewing on the plant will die, several applications are needed and must be used before insects arrive.
Bifenthrin found in products like Bifen IT and Talstar are a good contact insecticide.Lessor used ingredients carbaryl( Sevin) Permethrin and Esfenvalerate can also be useful.