Impact of insecticides used to control Spodoptera frugiperda (J.E. Smith) in corn on survival, sex ratio, and reproduction of Trichogramma pretiosum Riley offspring
Corn (Zea mays L.) is cultivated in large areas and considered one of the world’s major cereal crops. There are several arthropod pests that can reduce its production such as the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lep.: Noctuidae), which is considered to be the main pest for corn. Fall armyworm is primarily controlled by insecticides. The use of biological control agents to manage this pest is growing with an emphasis on the egg parasitoid Trichogramma pretiosum Riley (Hym.: Trichogrammatidae). Thus, the aim of this research was to evaluate the impact of the following insecticides (g ai L-1) beta-cypermethrin (0.03), chlorfenapyr (0.60), chlorpyrifos (0.96), spinosad (0.16), etofenprox (0.10), triflumuron (0.08), alfa-cypermethrin/teflubenzuron (0.0425/0.0425), and lambda-cyhalothrin/thiamethoxam (0.11/0.083) on survival, sex ratio, reproduction, and T. pretiosum offspring. Distilled water was used as a control. Commercial insecticide formulations were diluted in distilled water. Bioassays used Anagasta kuehniella eggs treated with insecticides which were afterwards exposed to parasitism. Bioassays were conducted under controlled conditions at 25 ± 2 °C, 70 ± 10% RH, and 12:12 h photoperiod. Alfa-cypermethrin/teflubenzuron, beta-cypermethrin, chlorpyrifos, chlorfenapyr, spinosad, etofenprox, and lambda-cyhalothrin/thiamethoxam reduced parasitism capacity of maternal generation females as well as the percentage of insect emergence from the F1 generation. Only triflumuron was selective for T. pretiosum and can be recommended along with this parasitoid in fall armyworm management programs in corn.