We've been shaking our plum tree for a few weeks and have seen only one curculio, the first time we shook the tree. Now, when virtually all the petals had fallen, we sprayed with Malathion. We are assuming we keep shaking the tree each morning to catch any curculios. If we continue to see none, do we need to spray again in 10 days? Do we need to keep shaking each morning? Are there other forms of the bug, besides the beetle, to watch for? We have had so many (apparently) in past years that the hundreds of fruits were all infested and fell when green. Where are they now?
Hennepin County Minnesota
If you do not see any bugs after shaking the tree, spraying should not be necessary. You should continue to shake the tree to monitor for the snout bugs until early June because cool weather can delay their attack. It is possible to effectively control plum curculio by shaking and killing the bugs that fall on the tarp.
Years ago when I had a plum tree I tried a control measure I read about that recommended smearing the main trunk and the first major branches with vasoline. Make a band around the trunk that is about 2 inches wide. This seemed to stop many of the bugs. Be sure to check out the fact sheet, not all years are as bad as the worst years and not all trees are attacked.