Monitoring of insecticide resistance in two populations of Chrysoperla externa (Neuroptera: Chrysoperla)

HARAMBOURE, MARINA; SMAGHE, GUY; NIU, J; MIRANDE, LUCIANA; GUTIERREZ, GUILLERMINA; GOETEYN, L; SPANOGHE, P; ALZOGARAY, RAUL A.; SCHNEIDER, MARCELA INÉS

Simposio; 66 International Symposium on Crop Protection; 2014

Although natural enemies are slow to develop pesticides resistance because of a combination of biological, ecological, and biochemical (lower detoxification capacity) factors (Roush et al. 1990), some predators or parasitoids have developed high levels of resistance in the field. A good example is the Paleartic generalist predator, Chrysoperla carnea (Neuroptera: Chrysopidae). C. externa is a native predator from the Neotropical region where it is considered as prominent candidate as biological control agent. Its larvae feed on several agricultural pests such as aphids, whiteflies, scales, and lepidopterans eggs. Previous studies have shown a high tolerance to pyrethroids in these species. In this project, we aimed to determine if resistance mechanisms exist in a field-collected population of C. externa compared with a laboratory strain. The laboratory strain was reared for four years and refreshed periodically from field specimens in crops without exposure to pesticides, and the field strain was collected in field vegetal crops (Great La Plata area, Argentina) with high sprayings of pyrethroids and neonicotinoids 6 months before bioassays. Firstly, the toxicity assays with a topical treatment with cypermethrin were done in third-instar larvae of predator with and without pretreatment with enzyme synergists PBO and DEF, which inhibit P450 mono-oxygenase and esterase detoxification enzymes, respectivelyAfterward, the activity of p450 enyzmes in both strains was measured in vitro with p-nitroanisol as substrate. Finally, larvae treated with cypermethrin alone and with a pretreatment with PBO and DEF were extracted and, the amounts of parent/non-metabolized cypermethrin were analyzed by gas chromatography. In conclusion, the field-collected strain of C. externa showed no resistance development against cypermethrin but the data confirmed the presence of P450 metabolism. The data are discussed in relation to the insecticide pressure in the field-collected strain and potential fitness costs.