A preliminary test using several different insecticides was carried on by the author as a mean to control the oruon thrips (Thrips tabaci Lind.) which has badly damaged onion crop in Central Chile since 1954. The tests were conducted in Quillota (Aconcagua, Chile), from November 1956 to February 1957, and included Aldrin, Metasystox, Dieldri-n, Metoxychlor, Toxaphene, DDT, Perthane, BRC, Diazinon: Lindane, Parathion, Malathion, and EPN 300.
Dieldrin 50% WP. proved to be the most effective insecticide at dosages of 2.0 kgs. per ha., with an active residual action oi 20 days. No phytotoxic action was detected.
Toxaphene E. 50 %, at dosages of 6 lts. per ha., BHC. WP. 10% y at dosages of 5 kgs. per ha., and Parathion 15% WP. at dosages of 3.3 kgs. per ha., were quite effective for 10 days. No phytotoxic action was detected either.

1 Ing. Agrónomo. Entomólogo