Q: I am being plagued by little green caterpillars raining down from oak trees on silk strands. The past two weeks literally thousands have descended onto my cars, home and driveway. They leave copious amounts of tiny black pellet waste.
A: It’s spring cankerworm. The caterpillars mostly feed in trees but I’ve heard reports of damage to roses too. Whatever their origin, they drop down from the plant on a silk thread before pupating in the soil. There is not much to be done when they are in a tree. You could spray the organic Bacillus thuringiensis (B.t., Dipel, Caterpillar Attack, etc) but getting it high enough to be effective would be difficult. I have more information, plus a recipe for cankerworm sorbet at xrl.us/cankerworm.