In Vivo Production of Agrotis ipsilon Nucleopolyhedrovirus for Quantity and Quality

The black cutworm, Agrotis ipsilon (Hüfnagel) (Lepidoptera: Noctuidae), is a pest causing damage to a variety of plants including turf and row crops. A recently discovered baculovirus has the potential to be developed as a microbial-based biological pesticide to provide targeted control of this insect pest. In an effort to develop this baculovirus as a biological pesticide, experiments were conducted to determine parameters necessary to maximize in vivo production using cutworm larvae. Treatment combinations including three larval diets, larval age at infection (6- to 10-d old), and dosage of virus exposure (1 × 105 to 1 × 108 occlusion bodies [OBs]/ml) were evaluated. Production quantity and quality were measured as number of OBs produced and insecticidal activity of the virus, respectively. Generally speaking, insect diets that maximized larval growth resulted in a greater quantity of virus OBs. Less virus was produced when younger (small) larvae were exposed to higher dosages of virus resulting in rapid mortality and when older (large) larvae were exposed to low dosages of virus resulting in low levels of infection. Virus quality was measured as insecticidal activity (low LC50 representing high activity) and was highest for larger larvae exposed to minimal virus concentrations needed to initiate infections. When considering both quantity and quality measurements, maximum production was achieved for 8- to 9-d-old larvae fed a general purpose lepidoptera diet. These results will support the development of this baculovirus as an additional tool for the integrated control of the black cutworm.