Don’t wait too long to combat squash borer

It’s gardening season and many new gardeners are setting

out to grow their own food. Weather conditions can be a big

challenge. Strong winds hinder young plants and baking sun

doesn’t help them either.

All that can pale in comparison to six legged vandals that

can destroy all your hard work. One day your squash plants look

great and the next one they’re wilted beyond hope. It’s enough

to make most people give up. To stop this scenario from

happening one must be observant and vigilant.

The culprit is likely the squash vine borer. They also

attack cucumber, pumpkin, cantaloupe, watermelon and any other

member of the cucurbit family. They’re a bigger problem on

pumpkins and squash because of the larger stems.

Squash vine borers look a little like bees or wasps but

they’re bright orange. Squash vine borers are actually a type of

moth. Adults are usually active during the day or near dusk. If

you see any, you must begin looking for small loose clusters of

yellowish tan colored oval shaped eggs. It’s important to

control this pest before the lifecycle proceeds much further.

If left uncontrolled these eggs will hatch and the larvae

will begin their voracious attack on your plants. These tiny

caterpillars bore holes into the stems and live there for

several weeks. Plants continue to grow for a while, but

eventually the damage is too much and they die almost overnight.

Adults lay their eggs on the basal stems so this is where

gardeners need to focus their attention first. Sometimes if

infestations are small, eggs can be destroyed before they hatch.

If larvae develop tougher measures will be necessary.

Many insecticides are partially effective for control of

this pest. Imidacloprid, a systemic insecticide, can be helpful

early in the season. It will kill these pests for three to four

weeks. However, this pesticide can’t be used when plants near

maturity, since residues might accumulate in the squash.

The bacteria Bacillus thuringiensis is a major component of

many garden insecticides designed to kill caterpillars. This

will kill the larvae of squash vine borers, but only if it

contacts them before they enter the stems. Once the critters get

inside the plant the pesticide is ineffective.

Some gardeners search for resistant varieties to this

insect. Actually, I know of no truly resistant ones, but some

types have tougher stems that make it harder for the larvae to

enter the plants. ‘Butternut’ is a winter squash variety that

generally is less affected by squash vine borer.

Some people also use row covers to prevent adults from

laying eggs on their plants. Row covers are a thin translucent

fiber material that let in light but seal out insects, birds and

other pests. Row covers make harvesting labor intensive and must

be completely reinstalled afterwards. Also, if not done soon

enough they are of no help at all.

To complicate matters further, there is a bacterial disease

spread by a little striped beetle that can cause very similar

symptoms. I’ll have to profile that problem next week.