I very much doubt the problem magically disappears with "newer" pesticides. Afterall, if a pesticide washed off in the rain, it wouldn't be much good as a pest

I very much doubt the problem magically disappears with "newer" pesticides. Afterall, if a pesticide washed off in the rain, it wouldn't be much good as a pesticide .... it would be a very expensive proposition for the farmer to re-apply after each rainfall.