Suppression of Fuller Rose Beetle (Coleoptera: Curculionidae) on Citrus with Steinernema carpocapsae (Rhabditida: Steinernematidae)

Abstract

A laboratory bioassay with larvae and adults of the Fuller rose beetle, Asynonychus godmani Crotch, and the Kapow strain of Steinernema carpocapsae (Weiser), resulted in 12, 44, and 67% mortality with rates of 50, 150, and 500 infective juveniles per 3-wk old larva, respectively; 100% mortality with 150 infective juveniles per 3-mo old larva; and 24, 48, and 83% mortality with adults. A field trial was conducted on Valencia orange trees harboring high levels of Fuller rose beetle late instar larvae. A single application of either the Kapow or All strain of S. carpocapsae each applied at 3 rates (50, 150, and 500 infective juveniles per cm 2 ) reduced the number of emerging adult Fuller rose beetles a combined 55 and 38% compared with the water control the year following treatment and 79 and 82%, respectively, the 2nd year. Because of high variability between treatments, however, it was difficult to choose between the two nematode strains or the 3 rates of each strain. Infested fruit was reduced by a combined mean level of 62% one year after treatment. Based on nematode recovery at 6 months and the further reduction of Fuller rose beetle emergence in the second year after application, we suspect that nematodes persisted and recycled in the soil and provided added control in the second year of the trial. In order to conduct the laboratory bioassay, a method of rearing Fuller rose beetle from egg to adult was developed. A corn rootworm artificial diet was used but resulted in high larval mortality. After 6 months on the diet under laboratory conditions, 12 parthenogenetic females resulted from approximately 1,000 eggs and 8 of these females produced viable eggs masses.