Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/19/2006
Publication Date: 10/1/2006
Citation: Arthurs, S.P., Lacey, L.A., Behle, R.W. 2006. Evaluation of spray-dried lignin-based formulations and adjuvants as solar protectants for the granulovirus of the codling moth, Cydia pomonella (L). Journal of Invertebrate Pathology. 93: 88-95. Interpretive Summary: Codling moth is the most serious insect pest of apple in the Pacific Northwest. The granulovirus of the codling moth (CpGV) has recently been registered as a microbial (environmentally safe) pesticide and is used by orchardists in this region to selectively control codling moth larvae. However, current commercial formulations have a short residual activity because the activity of the virus is reduced through sunlight (ultraviolet) exposure. This limitation means the virus often requires frequent reapplication during the growing season, thus increasing costs. In 2005 researchers at the USDA-ARS Yakima Agricultural Research Laboratory evaluated experimental spray-dried formulation of CpGV (lignin-encapsulated virus) for improved ultraviolet protection. Results showed that the new formulation provided significant protection and extended the residual activity of the virus exposed to ultraviolet radiation when applied at relatively high dosages.
Technical Abstract: Commercial insecticide formulations of the codling moth, Cydia pomonella L., granulovirus (CpGV) are have a short residual activity under orchard conditions in the Pacific Northwest. Most of the loss in virus activity is due to sunlight (ultraviolet exposure). This limitation means the virus often requires frequent reapplication during the growing season. We evaluated an experimental spray-dried formulation of CpGV (lignin-encapsulated virus) for improved ultraviolet protection. In laboratory tests with a solar simulator, lignin-virus formulations with and without additives (titanium dioxide and sugar) provided significant UV-protection of virus when applied at a high dosage of virus (3 × 1010 virus particles /L), i.e. 92-94% control compared with 67% from a commercial glycerin-stabilized product. The lignin-virus formulation was ineffective when a lower dosage of virus was applied (3 × 108 and 3 × 109 virus particles/L). We also tested several spray adjuvants (NuFilm-17, Organic Biolink, Raynox and Trilogy) but found they did not protect a commercial virus formulation from solar inactivation in laboratory tests. In orchard tests, the lignin-virus formulation did not improve control of codling moth or reduce fruit injury compared with a commercial virus formulation (both were applied at 6.57 × 1012 virus particles/ha). Our studies show that lignin-encapsulated CpGV formulations provide solar protection, but only at relatively high dosages. The testing of high concentrations of carrier containing reduced virus concentrations of virus would be worthwhile and may allow virus protection at more economical rates.