SHOP BY DEPARTMENT
daninthedirt

fear the borers no more?

OK, so I *think* I've learned how to avoid the squash vine borer (SVB), which I regard as the most serious insect pest in all of gardening. You west coasters don't know how good you have it, without having any SVBs. Sorry for the long post, but this needs to be reported.

There are several well known strategies. (1) Cover the whole bed with netting. That size netting is pricey and, besides, you'd shut off natural pollination. You've be pulling the whole net back every morning to hand pollinate. Yuck. (2) You carefully inspect the whole bed every day for larvae. You kidding? Yuck. (3) You do surgery on infected vines and pull out the larvae once established. Who wants to do that? Yuck. (4) It is said that placing up-facing paper cups around the base of the young plants works, but at least the second generation won't be deterred by that. They fly in. They don't come up from the ground like cutworms. I don't think there are any preventative insecticides that work well on SVBs. So, we got a problem.

But the strategy that is working for me is just waiting them out. I had a short post on this last year. Here is some more info. The life cycle of SVBs is well understood, and that's our tool.

Squash vine borers emerge from mature larvae or cocoons in the soil at about 1000 GDD (growing degree days, 10C base). This is a commonly quoted number. In Central Texas, for me, this is about late-March. Once emerged, females usually lay eggs one day after emergence, and the eggs hatch 14 days later. See https://entnemdept.ufl.edu/creatures/veg/leaf/squash_vine_borer.htm . The hatched larvae then burrow into the stems. That’s what kills the squash.

In the south, there is often a SECOND GENERATION of squash vine borers. Emergence of those is around 2500 GDD (10C base). https://eorganic.org/node/5300 This corresponds to about late-May in Central Texas.

That means that by June, egg-laying of the second generation is all done for me.

I used to plant out squash at the beginning of March, with everything else, and the plants were all dead by May. Every single year. I usually planted Butternut, and rumor has it that Moschata are "resistant" to SVBs. Well, down here they are not. That word belongs in quotes, because it's a squishy kind of word. It does NOT mean "immune". Not by a long shot. Maybe Texas SVBs are just tougher?

So what I've started to do is to plant out on June 1. Long after my other summer veggies. The plants are small, and a row is easily covered with a cheap length of yard-wide tulle. Extra security. No pollination needed then. They grow for a few weeks, and then when they get mature, and start to push out of the tulle and flower, you just pull the tulle off. Then it's off to the races, fruit-wise, with NO SVBs. As of now, I have sixteen squash coming off of three hills. Just harvested the first three today.

So how do you, in other areas, translate GDDs into dates? There are a few websites that help. You can try https://www.degreedays.net/. You want "cooling degree days" at 10C. You get an Excel file, and you'll want to add up the numbers, starting I guess at the beginning of the year. You could probably ask your local extension service for GDD info appropriate to your locale. Now, all of this being said, this may not work well up north. My growing season is about 300 days, and I can afford to lose a hundred or so of those days in the spring. Up north, your SVBs come out later, and your growing season is short. You probably can't afford losing those days.

This is the second season that I've avoided SVBs by doing this. Last year it worked well, but I planted in an area that didn't get enough sun, and the plants didn't thrive. This year, they get loads of sun, and they're going bananas. One thing I wonder about is whether our unseasonable arctic freeze in February of this year killed the eggs. But I'm guessing they were protected in the soil, and others in my neighborhood have gotten their early spring crops demolished by SVBs, as usual. I've heard this waiting-them-out trick talked about occasionally, but without any details.

Next year, I'm going to do zukes, which I've never dared try down here.

Comments (4)

Sponsored
Fitzgerald Home Furnishings
Average rating: 4.9 out of 5 stars28 Reviews
Loudoun County Quality Furniture, Cabinetry & Decor | Best of Houzz