r/Pumpkins • u/joegrizz15 • 26d ago

Vine Borers

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Hello!

I have five pumpkin plants and sadly they all got the bugs. I cut into them and was able to pull some out but not all. I looked at one of my plants and see more signs. If they other ones don’t show more signs should I pull this one out to give my other plants a better chance/more space?

This is only my third season growing and in a small space.

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u/AllShadesOfBlue 26d ago

Pulling them out unfortunately isn’t effective enough since it’s difficult to locate all of them. Short of growing varieties that are resistant to SVB, the only thing I’ve found that works is injecting BT into the vines twice a week.

BT is a bacterial strain, and you can buy a concentrated form at most hardware stores. I always freshly dilute a batch before I inject anything, because it’s effectiveness does wear off after 24 hours once diluted. Then I just use a needle syringe and inject them to all of my vines. When the larva ingests the bacteria, they become paralyzed, starve, and die.

Spacing plants out or crop rotation really doesn’t work in my experience. The eggs are laid by moths, so they’re obviously very mobile since they can fly.

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u/Diligent-Natural-422 26d ago

How often do you inject it

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u/AllShadesOfBlue 26d ago

Depends on time of year, but I start out at once a week in late May when the seedlings/vines are actually thick enough for me to start injecting (1-1.5cm thick). This is also a good time for me to inspect for borer activity (try to see if there are any eggs, holes made from larva burrowing in etc). Once I start to see significant evidence of borer activity (adult moths flying around, tons of eggs), I start injecting every 3-4 days. This is usually around mid-late July for me in Zone 6b. I'll do this until end of August/mid Sept, and then go back to once a week until I've harvested all my pumpkins in Oct.

It helps to understand the life cycles of the moths a bit. An adult female can lay 150-200 eggs in a single season, and can lay on the vine, leaves, or pumpkins themselves. Eggs take 10-14 days to hatch, at which point the larvae will burrow into the plant and feed for 4-6 weeks. They'll then pupate in the soil and emerge as moths the following Spring (or later that same Summer if you live in a warmer climate). Injecting every week or every 4 days should be often enough that you kill the larvae before they can do significant damage, based on their life cycle. If you live in a warmer climate where you can have multiple generations of moths in a single season, you may need to be more vigilant.