Infectivity of Two Strains of Steinernema feltiae (Rhabditida: Steinernematidae) in Relation to Temperature, Age, and Sex of Carrot Weevil (Coleoptera: Curculionidae) Adults

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Abstract
The effects of two strains of Steinernema feltiae Filipjev, DD 136 and Listronotus, on the survival and oviposition of carrot weevil, Listronotus oregonensis (Le Conte), adults of different ages and sexes were evaluated in the laboratory. The lethal tim50 (LT50) obtained for overwintered adults was significantly higher than those obtained for adults 1, 13, and 60 d old. When no feeding or ovipositing took place, the females had a significantly shorter LT50than the males. Although the availability of food decreased the LT50’s of males and females, oviposition did not increase the susceptibility of females. The DD 136 strain performed better than the Listronotus strain when the carrot weevil adults did not feed or oviposit. Both nematode strains decreased the oviposition rate of infected females before their death. The LT50’s for both strains decreased as temperature increased, but at 10°C, DD 136 had an LT50 shorter than the Listronotus strain.