A few days ago I decided to get serious about the aphid infestation in my chiles. So far I had tried insecticidal soap with pyrethrins, and Neem. The insecticidal soap/pyrethrin spray that I used was a disaster. I was not aware that the insecticidal soap could be phytotoxic to chile plants. The chinense plants seem to be particularly susceptible. My poor plants dropped most of their leaves and blossoms. Fortunately, the chiles that had already formed were not affected. However, I didn't get around to caging most of the plants for seed saving purposes until after the "treatment". Not only do I not have much of a chile crop, but I don't have many seeds to save - none for a few varieties. On top of all that, once the plants started to recover the aphids came right back.
By that time I had figured out the phytotoxicity problem. I decided to try Neem oil for the second aphid treatment. Neem works by preventing insects from developing, they can't molt to more mature stages. I also happened to be using Neem to fight powdery mildew on my zucchini (works great) so it was convenient (I'm lazy). At first it seemed that the Neem wasn't doing a thing. But, after about a week, I noticed that the aphid population was drastically reduced and over time they didn't seem to be coming back.....
Then, seemingly overnight, the caged plants were infested again. Only the caged plants. Okay, Neem again. But this time the aphids did not go away. And, for some reason, there were a bunch of male aphids flying around. It was getting really disgusting in there. Next treatment option: pyrethrin. Even though pyrethrin is an organically approved treatment I had hesitated to use it. First, it was part of the disastrous first treatment. Second, it is more toxic to benficials than Neem or insecticidal soap and I could see some parasitized aphids along with the tiny wasps that lay their eggs in the aphids. I hated to murder beneficial insects, but they were not keeping the infestation in check. I treated with pyrethrin anyway.
Today I checked up on the chiles. Dead aphids everywhere. And live beneficial wasps! The unhatched wasps must not have been hurt by the spray. Plus, the plants look okay too, well, no worse than they looked before.
Now I'm hoping that, with a little TLC, I can get the plants to survive through the winter. I've had pretty good luck with chiles in past years, but they've been healthier specimens.