I don't know which has been plaguing me, but I am wondering if its the southwestern one, because some of the things I read about them on the web are not true.
Here are some things I have determined to either be myths or maybe specific to the other species:
1. They lay eggs on the base of the vine. Not true. The lay them everywhere, at the tip of the vine, leaf stems, on top of leaves, everywhere!
2. They come out early morning or evening. Not true. I have mostly seen them when I am home on the weekends, usually between 10AM and 2PM is when they seem most active.
3. They have 2 generations in the south- Now many folks say there is 1 generation up north, and 2 or 3 in the south. In my experience, its been a continuous deal... they don't take much of a break down here.
The eggs are small, reddish brown disks. Here is a pic: (picture below not mine, copied from web search)
These eggs hatch into larva that burrow into the plant, and eat it from the inside, and can kill the plant if eats enough to cut off the water/nutrients to the rest of the plant. Its truly a terrible pest, because you often cannot see the damage until it becomes extensive.
Earlier in the spring, my first run-in with these was with my acorn squash plants. Since I planted them early, I was able to harvest a good 5 or 6 squash before the plants died, but I was not sure why their vine rotted away causing them an early death. I also planted some yellow squash but those were quickly infested and I lost all the plants. So I did research and found it it was the SVB. At that time I had replanted more acorn squash, and found out those got infected too, but having more knowledge now, I was able to fight them for a while.
Here is my battle plan that I drew up back in late July, based on what I had read online about them. I wanted to stay organic, because I didn't want to harm bees or beneficial insects, like the assasin bugs that I had a lot of, and wasps too. I even had an anole and a toad that hung around too.
My initial SVB Battle Plan:
1. Every day go out and pick off all the SVB eggs I can find.
2. As the plant grows, pile up more dirt around the stem, to encourage more root growth.
3. Spray with NEEM oil, once a week. I read its supposed to build up in the plant and act like a systemic insecticide.
4. As the plants get bigger, monitor for holes with frass coming out. Then inject BT (
Bacillus Thuringensis) solution above the holes. I might just inject anyway periodically for good measure.
5. Go out at night and flash a light on the stem, and spot the worms, and stab them to death with a needle.
OK, so its 9/14 now, how did it go? Well season's not over yet but I have a good idea of what has worked and what has not.
Item #1: - This is very time consuming. Its effective if you can find all the eggs and pick them off. What helps is that they take a number of days to hatch, and they are pretty conspicuous. But what makes it hard is that they sometimes lay eggs under vines where its hard to see. They can lay them anywhere! So its easy to miss a few eggs. As the plant vines get long, this becomes an even harder task.
Item #2: That works good in encouraging roots, and can save a plant. But a big drawback is the if they lay eggs on the leaf stems and you miss them, they will bore down the stem into the buried vine. Then that portion of the vine might start dying, and you cannot see it. What I did with my pumpkins that I think helps is whenver I see stems with signs of damage, I inject BT into those stems, and let the BT run down inside into the vine.
Item #3: The Neem product I tried was pretty ineffective, as it didn't discourage any egg laying, and the plants got attacked, even by aphids. I later found out I didn't really use pure neem oil. My product, Fertiloam Triple Action Plus, actually only had "Clarified hydrophobic extract of neem" which has had the most important ingredient, azidaractin, removed and sold as a separate product. What a rip! So my experiment is inconclusive. I may try again next year with real "100% pure cold-pressed" neem oil.
Item #4: This seemed to work, but the problem is that the vines grow very long, and proactively injecting the vines every few inches is a lot of work!! So I decided to wait until I see damage and them inject. But the problem is by the time you see damage, the plant has suffered. But overall I'd say BT injections are worth the effort, and I'll keep using it. I used the liquid concentrate and diluted it about half as much as the directions.
Item #5 - That didn't work. Vines were too numerous, and since my plants were to cramped together it was too hard to do. This would be way too time consuming.
OK so given what I know now, here is my plan for next year:
1. Cover all squash/pumpkins with tulle netting. Keep the cover on until I have a good number of female flowers.
2. As they are covered, remove the covers periodically to dig in vines under dirt, and quickly replace cover. Keep doing this as they grow to form stronger vines.
3. Uncover and hand-pollinate at first. Then when sufficient female flowers appear, remove the covers.
4. Start the egg patrol. Remove all eggs I see. Keep burying vines. Inject BT when I see any sign of damage.
Hopefully this plan will allow me to have a much better harvest before my plants eventually succumb, whether to the heat or cold, or aphids, or powdery mildew, or the SVB.
This is good info, a friend was asking me about SVB recently and I don't grow squash. I can direct her here next time.
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