Insecticidal effects of turmeric powder and derivatives from Curcuma longa (Zingiberaceae) rhizomes against the cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae) in the laboratory and greenhouse

Turmeric, Curcuma longa L. (Zingiberaceae) is a small rhizomatous perennial herb originating from southeast Asia, most probably India. The plant produces fleshy rhizomes of bright yellow to orange color that are the source of the commercially available spice turmeric. The powder is used as a spice, food preservative, and food-colouring agent, but  is also well known for its medicinal and pesticidal properties. We have investigated the insecticidal effects of turmeric powder, crude essential oil, curcuminoid pigments, and ar-turmerone isolated from turmeric powder and crude essential oil, respectively against cabbage looper larvae. Twenty-four hours after topical application of 10 µg to third instar larvae, mortality ranged from 20-30%.  Cabbage looper larvae demonstrated 50% growth reduction compared to controls after being placed on cabbage plants treated with 1% crude essential oil or 1% ar-tumerone in the greenhouse for four days. Numbers of larvae recovered on ar-tumerone-treated plants was only 60% of those on control plants. Turmeric products have some potential to be used as inexpensive and environmentally safe alternatives to chemical pesticides.