Production of nuclear polyhedrosis virus of Anticarsia gemmatalis Hübner (Lepidoptera:Noctuidae): effect of vírus dosage, host density and age

The laboratory production of Anticarsia gemmatalis Hübner nuclear polyhedrosis virus (AgNPV) was evaluated for larvae inoculated at 1.0, 1.5, 2.0, and 2.5 cm and with two NPV dosages, 10(6) and 10(7) polyhedron inclusion bodies (PIB)/ml, sprayed on the insect diet surface. A fixed population of 25 larvae/300-ml cup was used. Highest virus yield was achieved for larvae inoculated with ca. 2.0 cm at the higher NPV dosage. Losses of NPV-inoculated larvae ranged from 42.4% to 64%, due to high incidence of canibalism, death by other causes, and pupation. In another experiment, larvae were inoculated with two NPV dosages (1.0 x 10(7) and 4.0 x 10(7) PIB/ml), using 25,20, and 15 larvae/cup at the beginning of 4th instar (B4L); end of 4th instar (E4L); beginning of 5th instar (B5L); and end of 5th instar (E5L). Highest NPV production was attained for B5L at 25 larvae/cup, for both dosages, with a production efficiency of ca 90%, in spite of a decrease in PIB/larva and an increase in canibalism with the increase in larval density. Better standardization of larvae at inoculation improved efficiency in NPV production.