Here in Los Angeles, I have three avocado trees. They bear fruit if they are properly pollinated, and it's bees that are best at doing that pollinating. To welcome the bees, we let the sorrel grow under the trees. About 10:00 a.m. each morning during the blooming season (just now ending), the sorrel beneath the trees and the blossoms in the trees are teeming with buzzing bees. It's a beautiful sight. Nature at its most harmonious.
One year, I noticed that an insect was attacking one of my pots of plants near my largest, most prolific avocado tree. And of course, I did what most gardeners would do. I went to my nearest gardening store and bought an insecticide.
I sprayed the insecticide once on one plant on one day. Next day, I noticed that the bee population had fallen. I missed the buzzing and the flitting of the bees from flower to flower on the sorrel, from bud to bud on the avocado trees. I had read about the potential threat of nicotinoids to bees and, remembering what I had read, checked the bottle of insecticide. And, yes, it was a nicotinoid.
I can't say with certainty that the nicotinoid caused the decline in my bee population. And the bees did return. We even saw a black one in our front yard on the rosemary recently. But my impression and my honest opinion is that the nicotinoids did cause the deaths or disappearance of some of my bees, a lot of my bees.
I encourage weeds and flowering plants in my garden because they draw bees. Gardeners need to be very careful about using nicotinoid insecticides and herbicides. Personally, I think that both kinds of products can endanger bees -- the nicotinoids more directly but the herbicides indirectly by killing weeds that draw the bees to the garden.
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