As I've said before, the best defense against them is manual inspections.
If you are finding multiples of them per cola, than you need to do a better job of inspecting. Being as blind as a bat makes it difficult.
You really want to be inspecting so diligently so that you can get them while they are young. They like to hide inside the nooks and crannies (as you know, some varieties bore into and traverse through the hollowed out stem system) Others, inch their way up and down the main stems of colas.
Again, my method of inspecting, which is the safest and most sound alternative to spraying (which I really like to avoid spraying if I can because the worms are found Deep inside the buds, spraying the buds will likely have no affect, in other words the worms are feeding on tissue that wouldn't be exposed to the toxin unless you dunked the entire plant in it) is to carefully examine each nook and crannie, and if I see worms I bring them out using a small ice-pick so that I don't have to cut or remove anything. This depends heavily on the variety because the boring type has a mold inducing saliva that makes it easier to penetrate the tough and fibrous cellulose of the stems, with those, you really have no choice but to just cut the colas. But for green loopers, since their saliva doesn't induce mold, I can skewer them right out and let the bud continue growing.
I've been in situations where I'd lose everything, and so when I have the green loopers I am thankful that I can remove them by hand without damaging the flowers.
So, really, I personally would not spray since it's just a little too close to harvest.... up to you though.. There are growers that I know who completely soak/drench their plants all the way up until the week before harvest, since BT degrades rather quickly in light, and if it dries quickly you'll be OK but again no guarantee because they're hiding deep in there... for me in general, I do most of my spraying during the earlier weeks of flower to fend off the small worms that you cannot see (which later grow to be larger as the buds grow and offer more sanctuary), and as we get to late flower the only thing I can do is Hope and Pray, in combination with my handy-dandy ice-pick.
Another thing you need to give thought to. Pay attention very closely to the activity of moths and butterflies. The moths are more treacherous. The humidity and night time temperature can stimulate their activity. Ramp up or plan your inspections according to the peak flight times #1 and #2 which are associated with June/July ----> to August and September.
Peak Flight times will vary according to region, so it's important to pay attention to when the most amount of mating takes place. It turns out that peak flight time #1 really does not affect you so much, since hard flower and true vulnerability doesn't occur until August and Sept. (PFT #2)... but they can get the foliage and be annoying during #1....
It's peak flight time #2 we have to prepare for. So knowing when exactly peak flight time #2 occurs in your area may help you pinpoint, and put up the best possible chance of growing clean and non-infested buds...Some food for thought.
Good luck, we are all battling the same issues, some people have it worse than others. It's all apart of the job at the end of the day, but there are a few varieties of the worms that, if they infested your colas, I would not wish that upon my worst enemy.
.... I hate growing outside and won't ever do it again. It really doesn't matter if I grow bigger buds outside if I won't smoke them cause of spider mites and worms........
