So, I tossed two of my zucchini plants in my compost tumbler yesterday, when pulling them up I didn’t need to uproot them, the squash borers had basically destroyed the main stem to the point that the top of the plant was hardly connected to the roots at all.
I knew it was squash borer damage, I had seen the tell tale signs of the orangish sawdusty wounds around the base of the vines, but I also knew it was too late by the time I noticed. But, this morning, I went out and did surgery on my remaining squash vines, and look what I found. You can cut the vine lengthwise, opening it up, and remove the borers manually, there will be small ones, the size of a couple grains of rice, and possibly big ones as you see. Ugly little things. They’re like big grubs with black heads. They burrow through your vine, killing it, then overwinter in the soil in a cocoon, to emerge in June as a giant fly-wasp-moth-thing and destroy your current crop.
So, after infestation, you can control it with the surgery as I explained, then immediately cover up the cut areas with a mound of dirt to protect it and hopefully encourage new rooting. You can also make sure leaf nodes further up on the vine root by putting mounds of dirt on them, this will mitigate the loss if the borers destroy the main vine. If you catch it early enough, when they’re still little orange or brown eggs on the vine OR have not yet made it inside, you can spray the vines with an insecticide and kill them. You can also go after the adults.
As I said the adults are giant fly moth things. They literally look like the biggest flies you have ever seen, or a type of wasp, with hairy legs, but they’re a type of moth (just with clear wings). They often have red or orange markings, but the ones around my house seem mostly black. They can be seen on or around the plants at various times in the day, especially evenings, and should be attacked and dispatched in your most ninja-esque fashion.
If your vines have been compromised, you can put them in a compost tumbler, but I would not put them in a compost bin or pile. In a tumbler you’ve got a more or less enclosed contraption that gets very hot in the inside AND is not open to the soil at the bottom. This should prevent any larvae from surviving. In a free form pile or bin where it is open, doesn’t get as warm (or turned as often & violently), they could probably survive to torment you next year. So if you do not have a tumbler, I would burn the vines, and as soon as possible after removing from the garden. You don’t want any of the larvae to escape and burrow into the soil.
These critters will attack all members of the squash family, so that is summer squash, hard winter squashes, pumpkins, etc. Apparently ‘Hubbard’ winter squash is the most susceptible, and butternut squash the least. One solution some gardeners do is to plant ‘Hubbard’ early in the season as bait, and then once it gets infected, pull it up and burn it. I’ve also read that wrapping nylon or another barrier around the stems can help as well. Personally, I think I will just spray with an insecticide. I try to do things organically and healthy and everything as much as I can, but I’m not broadcast spraying, I’m not spraying the parts I eat. I am only going to be spraying very specific spots on the vines. I’ll be using Sevin, others that work are apparently methoxychlor, rotenone, pyrethrum, and malathion.
Apparently their only natural pedator is wasps, which only get them as eggs or before they bore into the vines.