Zucchini in Texas is a lot of work. We have these nasty little moths that look a lot like orange wasps. They lay their eggs (see above picture) on zucchini stalks. The little worm that hatches bites into the stems and begins to eat the plant from the inside out. Yeah–science fiction in the real world.
The thing that works best is to build a screen cage and keep the plants covered from 9:30 or 10 in the morning until late afternoon. The moths are daylight flyers and they don’t get up terribly early. I leave the cages off at night and early morning until the blossoms close (this allows the bees to pollinate). I also pick the eggs off if any of the moths get inside or lay early. I check the plants every day for the eggs. My plants are also in the ground as early as possible–this usually means March. If they freeze, I try again. The moths start showing up about the last week of May in central Texas–right about the time the plants start to set fruit.
Here are some other experiments I’ve tried.
BT Worm Killer Experiment:
Summary – this can stave off death of the plant for perhaps an extra two weeks or so, but it is a lot of work. Meanwhile, you may get a few more squash. I also wind that stretchable band-aid stuff (the kind that is very flexible and sticks to itself) along the main stalk. This helps keep moisture in the main stalk even after the worms have drilled into it and made holes. It also keeps the moths from laying as many eggs along the stalk because it is not available to them.
Here is a link to the worm killer–this is a great product for spraying for Tomato Horm worms and other worms. Organic BT Worm Killer. I use BT worm killer because it only harms worms and nothing else!
I do think the worm killer works, but injecting it is far too much work for zucchini and other squash plants. There were some leaves/stalks where the worm did a bit of damage–but then the damage stopped and there was no worm. The leaf continued to thrive. I cut a couple of these leaves off and inspected them pretty carefully.
The overall problem is larger of course. The moth lays so many eggs (I found about 10 per moth visit) it’s impossible to find all the worms and kill them in time. The eggs are much harder to see near the soil or on the main stem.
Here’s a picture of a moth–I didn’t take it because when I see them, I kill them if I can. I tried to make sure the credit for the photo showed up. The ones I’ve seen are actually a very bright orange with blue on the side–quite pretty. And deadly for your plants!
Update: I’ve had a lot of questions about cutting off leaves and or the leaf stems and whether it will kill the plant: Yes, you can cut some of them off. I have cut several away as time has gone by–the worms entered the stems of the leaves and left evidence. If they are close to the main plant stem, I definitely recommend cutting the whole leaf/stem away from the plant. If they are not, you can inject the BT Worm Killer into the hollow leaf stem. The BT worm killer does seem to work after about a day.
I also inject the BT Worm Killer into any infected parts of the main stem. It’s hard to do because the main stem is not hollow, so you kind of have to hunt out the part where the worm has eaten it away. At this point, my plant stem is large enough that it has withstood two or three worms–so if you see frash (worm poop!) don’t give up. Try the BT worm killer, try to follow the path of the worm with a thin, sharp object and kill it.
After years of growing these things, screening them off in the daytime with row covers is really the most effective way to protect the plants. If a moth does lay eggs and they hatch, the BT work killer is a last resort.