Bt shouldn’t be recommended. please stop
It doesn't do a lot of good to go "organic" if you don't know the side effects of the measures you take. Bt is one that makes folks like me weep. yes, it kills the caterpillars of sulphurs, among whom are the White Cabbage butterfly. but it also kills monarch and swallowtails, painted ladies and Fruitilaries. there are ways to deal with the cabbage bugs and the squash bugs. Beneficial nematodes is one, a daily walk through the garden is another. but, at the very least, if you mention Bt OR tachnid wasps, please make a note that home gardeners, seeking to attract or even hand raise butterflies (as I do) should not use them. Nothing breaks the heart of a butterfly person more than, having found eggs in their yard, seeing tachnids come oozing out instead of our lovely little caterpillars, or, worse, just before or after going into a chrysalis, instead of a beautiful butterfly emerging, we get a maggot of tachnid. except, perhaps, Bt, the bacteria that allows us to raise our cats for a few days until one day, they fall off their milkweed, curl up and puke and poop green ooze and die. there are palces for these methods, but it is not in a pollinator friendly yard. these methods are technically organic, that does NOT make them good for the environment at all.
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