A novel formulation technology for baculoviruses protects biopesticide from degradation by ultraviolet radiation

Abstract

Biopesticides are biological pest control agents that are viewed as safer alternatives to the synthetic chemicals that dominate the global insecticide market. A major constraint on the wider adoption of biopesticides is their susceptibility to the ultraviolet (UV: 290-400 nm) radiation in sunlight, which limits their persistence and efficacy. Here, we describe a novel formulation technology for biopesticides in which the active ingredient (baculovirus) is micro-encapsulated in an ENTOSTAT wax combined with a UV absorbant (titanium dioxide, TiO₂). Importantly, this capsule protects the sensitive viral DNA from degrading in sunlight, but dissolves in the alkaline insect gut to release the virus, which then infects and kills the pest. We show, using simulated sunlight, in both laboratory bioassays and trials on cabbage and tomato plants, that this can extend the efficacy of the biopesticide well beyond the few hours of existing virus formulations, potentially increasing the spray interval and/or reducing the need for high application rates. The new formulation has a shelf-life at 30 °C of at least 6 months, which is comparable to standard commercial biopesticides and has no phytotoxic effect on the host plants. Taken together, these findings suggest that the new formulation technology could reduce the costs and increase the efficacy of baculovirus biopesticides, with the potential to make them commercially competitive alternatives to synthetic chemicals.

Figure 1

Efficacy of different NPV formulations following exposure to simulated sunlight in an ATLAS SUNTEST XLS + cabinet on glass slides for up to (A) 16 h and (B) 96 h. In both (A) and (B), three formulations were tested: non-formulated NPV (black symbols and lines), a commercial standard, LITTOVIR (blue symbols and lines), and NPV formulated in ENTOSTAT wax with Titanium dioxide, TiO₂ additive (red symbols and lines). Symbols indicate the means and bars are ± S.E. Symbols are staggered slightly for clarity. The equivalent hourly dose of UV is 234 kJ m⁻².

Figure 2

Efficacy of LITTOVIR and ENTOSTAT-TiO₂-encapsulated NPV formulations following exposure to simulated sunlight up to 16 days in a constant environment room on tomato and cabbage plants. Cabbage = circles, solid line; Tomato = squares, dashed line. Symbols are staggered slightly for clarity. Larval mortality in the control group (dH₂0 only) averaged 10–20% (data not shown). The equivalent daily dose of UV is 499 kJ m⁻².

Figure 3

Effect of TiO₂ and NPV on larval mortality. Bars indicate the means and error bars are ± S.E. Comparison with Control: (GLM: ***P < 0.001, ^nsP > 0.05).