HOST-SPECIFICITY AND BIOLOGY OF SPODOPTEA-PECTINICORNIS (LEPIDOPTERA,NOCTUIDAE), A BIOLOGICAL-CONTROL AGENT OF WATERLETTUCE (PISTIA-STRATIOTES)

The noctuid Spodoptera pectinicornis (Hampson) from southeast Asia was studied in quarantine for potential use as a biological control agent of the floating aquatic weed waterlettuce, Pistia stratiotes L. Host- specificity tests were conducted on 70 plant species in 32 families. F irst instars fed slightly on 5 plant species and moderately on 1. Thir d instars fed slightly on 7, moderately on 5, and heavily on 3 plant s pecies. In all tests, no larvae lived longer than 6 days or developed to the next stage except those on impatiens (Impatiens balsamina L.). In whole-plant tests of impatiens, larvae fed for several weeks, but w ere unable to complete development. In multichoice oviposition tests, moths laid over 70% of their egg masses on waterlettuce, 21% on nonpla nt surfaces, four masses on eggplant (Solanum melongena L.), and one m ass each on 4 other plant species. No eggs were laid on impatiens. The inability of larvae to develop to the next stage except on whole plan ts of impatiens, on which they did not advance to the pupal stage, and the nonchoice of impatiens for oviposition indicate the safety of S. pectinicornis for release. Species from genera with mostly polyphagous members should not be rejected from consideration as biological contr ol agents of weeds without testing. Areas other than the apparent cent er of origin should also be explored to discover newer insect-plant as sociations. Information on the biology of S. pectinicornis is also pre sented. (C) 1994 Academic Press, Inc.