|Javaid, Iqbal - UNIV OF MD, EASTERN SHORE|
Submitted to: Kluwer Academic Publishers Netherlands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 13, 2003
Publication Date: November 3, 2003
Citation: Farrar, R.R., Shapiro, M., Javaid, I. 2003. Photostabilized titanium dioxide and a fluorescent brightener as adjuvants for a nucleopolyhedrovirus. Kluwer Academic Publishers Netherlands. 48:543-560. Interpretive Summary: For many years, scientists have attempted to use nucleopolyhedroviruses (NPVs) to control insect pests. NPVs are natural viruses. Each kind of NPV kills only one or a few species of insect. NPVs are harmless to humans, plants, wildlife, bees, and beneficial insects. Because they are specific, they would be good alternatives to chemical pesticides, However, attempts to use NPVs to control insects have met only limited success. Among the most serious problems is the fact that NPVs are very sensitive to ultraviolet light (UV). When NPVs are sprayed onto a plant, sunlight often destroys them before they can infect insects. Many different materials have been added to sprays of NPVs to protect them from sunlight. Among these materials is titanium dioxide, with which some success has been obtained. However, common forms of titanium dioxide react with sunlight and water to form hydrogen peroxide, which can also destroy NPVs. We tested a new form of titanium dioxide that has been altered to prevent the formation of hydrogen peroxide. This form of titanium dioxide protected the NPV of the corn earworm better than conventional titanium dioxide. This finding is expected to lead to improved formulations of NPVs, which should make them more attractive to farmers and lead to improved pest control while minimizing problems associated with chemical pesticides.
Technical Abstract: Titanium dioxide reflects ultraviolet light (UV), and could be expected to protect nucleopolyhedroviruses (NPVs) from degradation by sunlight. However, in the presence of sunlight and water, titanium dioxide catalyzes the formation of hydrogen peroxide, which can degrade NPVs. We tested microfine titanium dioxide, in which the particles were coated to prevent catalytic activity, thus photostabilizing it, as a UV protectant for the NPV of Helicoverpa zea (Boddie). We found no evidence that this material would influence larval feeding rates. In the absence of UV, activity of the virus was reduced by nonphotostabilized titanium dioxide but was unaffected by photostabilized titanium dioxide or by zinc oxide. Under simulated sunlight, photostabilized titanium dioxide protected the virus to a greater degree than did zinc oxide. Photostabilized titanium dioxide was compatible with the fluorescent brightener Blankophor HRS. Under simulated dsunlight, both materials increased activity of the virus, relative to a virus with neither material, in a largely additive manner. In bioassays of foliage collected from fields of lima bean plants sprayed with the virus with or without one or both of these materials, titanium dioxide increased persistence of the virus, but Blankophor HRS had no significant effect.