Catalpa Worm Control: Using Bt for Caterpillar Management

Catalpa worms (caterpillars) defoliate trees annually, creating a mess. The easiest control is Bacillus thuringiensis (Bt) products—Green Light Worm Killer, Dipel, Caterpillar Attack. Apply in late July with a hose-end tree sprayer, repeating every two weeks through August. The challenge is reaching the canopy, but good water pressure with a long-necked sprayer can do the job.