The Q&A Archives: Caterpillars On Coneflower

Question: My purple coneflower has suddenly been infested with small black caterpillars. They are 20mm long, 4mm in diameter, and fuzzy. What are they? Can they be controlled with dipel? How long will it take the dipel to go away and allow butterflies to make larvae?

Answer: Echinacea, Purple Coneflowers, are way up there on the list of butterfly attracting plants. Butterflies have a tendency to lay their eggs near an abundant source of food, so the black caterpillars may very well be the larvae of butterflies. When Entomologists identify a caterpillar, they look at body size and color, but also at head capsule, arrangement and length of hairs, prolegs and other identifying marks. Without knowing what the caterpillar is, I'd be reluctant to use any insecticide, for fear of destroying the next generation of butterflies. Why not take a sample to your local Cooperative Extension office for a positive i.d.? (1026 Golf Ln., Murfreesboro, 37129; 615-898-7710)

Dipel, or Bacillus thuringiensis, is a bacterium that acts as a stomach poison. It's fatal to caterpillars when they consume plant parts treated with Bt. The chemical breaks down rapidly in sunlight and should be completely gone from plant parts in 7 - 10 days. But, if you treat your flowers now, you may be destroying the next generation of butterflies. Why not take a sample of the pest to your local cooperative extension office for a positive i.d. and suggested control?

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