Answer: I'm not sure what your "cone" is all about, though it sounds like it may be a pheromone (chemical lure) trap for adult moths. Such traps attract only one species of insect, so if the pest you describe is not the one it controls, then it won't do any good. If it designe for your pest, then the adults have already been to the area and laid their eggs, then it won't control the current batch of caterpillars. If this particular species reproduces more than once in a season, then it should help reduce numbers of future generations.
If you want, you can send a sample of the caterpillars to your agricultural extension office (ph# 616/383-8830) to be identified. Once you have the name of the critter, we can give you more specific information on how to repel it in the future.
As for these fuzzy culprits, you can knock them off the branches with a strong spray of water from your garden hose. Since they are confined to just a few branches, they won't cause long-term damage to the tree (most healthy trees can withstand two consecutive years of total defoliation before it kills them).
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