Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2003
Publication Date: 7/1/2003
Citation: BEHLE, R.W., TAMEZ-GUERRA, P., MCGUIRE, M.R. FIELD ACTIVITY AND STORAGE STABILITY OF ANAGRAPHA FALCIFERA NUCLEOPOLYHEDROVIRUS (AFMNPV) IN SPRAY-DRIED LIGNIN BASED FORMULATIONS. JOURNAL OF ECONOMIC ENTOMOLOGY. 2003 v. 96(4). p. 1066-1075. Interpretive Summary: The baculovirus known as AfMNPV has the potential to be developed into a biological insecticide for control of several important caterpillar pests. Unfortunately, dried virus often loses activity during storage and when exposed to natural sunlight after application in the field. An encapsulated formulation has been developed specifically to prevent inactivation by sunlight. Also, several ingredients and storage temperatures were studied for their benefit for extending shelf stability of this dry formulation. This research showed that encapsulated formulations of virus lost activity after 3 months storage at 30 C, but did not lose activity when stored in a refrigerator for over 2 years. Encapsulated virus also had improved residual activity when applied to field grown plants, when compared with unformulated virus. This work demonstrates the benefit of specific formulations and storage conditions on the viability of the virus. These results will benefit the biopesticide industry by providing basic and applied information relative to the production of virus-based insecticides.
Technical Abstract: A multiple-embedded nucleopolyhedrovirus isolated from Anagrapha falcifera (AfMNPV) has potential to be developed into a microbial bioinsecticide. We tested spray-dried AfMNPV formulations after storage for insecticidal activity based on bioassays with neonate Trichoplusia ni (Hübner). Eight experimental lignin-based spray-dried formulations, a glycerin-based formulation, and an unformulated sample made with virus stock were made from three commercial production lots for testing. Samples of these formulations were stored at 30 C in individually sealed sample containers for destructive sampling after 1, 3, and 6 months while the remaining product was stored in glass jars under refrigeration for up to 30 months. Spray drying did not significantly reduce the initial LC50 of AfMNPV in experimental formulations compared with unformulated virus that was not spray dried. Refrigerated storage for 6 months did not significantly lower virus activity of formulated samples compared with the unformulated AfMNPV stored frozen, while storage for 30 months slightly decreased activity, expressed as higher LC50 values determined for both droplet and leaf feeding assays. When stored at 30 C, most formulations (22 of 24) maintained insecticidal activity for 3 months, but most (21 of 24) lost significant activity after 6 months' storage. The glycerin-based formulation also lost activity within 6 months of storage at 30 C when compared with frozen unformulated virus, but did not lose activity when stored refrigerated for up to 30 months. These formulations were evaluated after 7 months at 4 C for residual insecticidal activity when applied to field grown cabbage. Insecticidal activity was determined against T. ni neonates for treated leaf samples collected at 3, 7, 27, and 51 h after application of 2.5 x 10(12) pibs/ha. Field tests showed no differences in activity among samples of dried stored formulations and one freshly made formulation. Spray-dried formulations had significantly higher insecticidal activity (67.5% mortality) compared with the unformulated treatment (30% mortality) sampled 3 h after application. At 3, 7, and 27 h after application, the spray-dried formulations had higher residual activity (67%, 59%, and 42% mortality, respectively), compared with the commercial glycerin-based formulation (61%, 38%, and 23% mortality, respectively). These experiments demonstrated that AfMNPV in lignin-based spray-dried formulations had a shelf-life of up to 3 months at 30 C and up to 30 months at 4 C, and with longer residual insecticidal activity in the field compared with unformulated or a glycerin formulation.