Lethal and sublethal effects of lufenuron on the predator Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae)

Abstract The neuropteran Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) is a generalist predator present in Mediterranean agroecosystems. It has a wide range of prey including almost all soft-bodied arthropods; its voracity makes it a suitable agent for inclusion in Integrated Pest Management (IPM) programmes. Use of insecticides that inhibit chitin synthesis has increased and includes the use of benzoylureas (e.g. lufenuron) which negatively affect development of the immature stages of phytophagous insects, both by ingestion and by contact. This study evaluated interactions between lufenuron and the predator C. carnea in the laboratory. Treatment of eggs with lufenuron 24 or 48 h after oviposition had no effect on the proportion successfully hatching, or in the survival of resulting neonate larvae. Topical application of lufenuron to second instar larvae (L2) of C. carnea resulted in high mortality rates; lethal concentration to kill 50% (LC50) was 0.0153 ml/L (0.00860–0.0236 ml/L). Moreover, the development time of third-instar larvae of C. carnea that had consumed prey treated with lufenuron 24 h previously (at a dose of 1 ml/L) was significantly truncated and high percentage mortality was observed when these larvae reached the pupal stage. In choice bioassays a high percentage of C. carnea larvae chose prey treated with lufenuron in preference to untreated prey. Ingestion of lufenuron by C. carnea adults had no effect on female fecundity or adult longevity, but caused a significant reduction in the viability of resulting eggs. In light of these results, the developmental stage of C. carnea should be considered when deciding on the timing of lufenuron applications within IPM strategies.