NATURAL CONTROL BY PREDATORS OF RACHIPLUSIA-NU (GUENEE) (LEPIDOPTERA,NOCTUIDAE) ON PHASEOLUS BEANS IN CENTRAL CHILE

In Colina, Metropolitan Region of Chile, the following predators of Ra chiplusia nu (Guenee) were collected on Phaseolus vulgaris L. beans: t he hemipterans Orius sp. (Anthocoridae), Geocoris sobrinus (Blanchard) (Lygaeidae), Nabis capsiformis Germar, and N. punctipennis Blanchard (Nabidae), the coleopterans Eriopis connexa (Germar), Hippodamia cent Guerin, and H. variegata (Goeze) (Coccinellidae), and spiders Thomisid ae and Anyphaeniidae. In a farm where no insecticides were applied, th e number of R. nu larvae decreased when nabids and spiders increased. In another farm, an application of deltamethrin reduced the larval pop ulations of the noctuid, but affected also the populations of predator s, except for Orius sp. Nabids, however, recovered their populations ( spiders also showed a tendency to recover) on the last sampling date. An application of cypermethrin in a third farm 8 days before the first sampling date diminished the populations of insects, although a susta ined increase of spider density was observed. These contributed to the general decrease of insects observed in this farm. A sulphur treatmen t applied at the middle of the flowering period in a fourth farm had a small effect on R. nu larvae, but had a repellant action against nabi ds and coccinellids. Laboratory observations of predators paired with R. nu eggs or larvae verified that Orius sp., G. sobrinus and the cocc inellids fed effectively on eggs of the nocuid, and that both nabids c onsumed preferentially small and medium size larvae.