Laboratory Evaluation of New Ultraviolet Absorbers for Protection of Douglas-fir Tussock Moth (Lepidoptera: Lymantriidae) Baculovirus1

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Abstract
In 1975, the Forest Service (USDA) recommended use of the adjuvant Shade as a UV absorber in spray mixes of TM BioControl-1, the nuclear polyhedrosis virus (NPV) of Orgyia pseudotsugata (McDunnough). Because Shade is no longer available commercially, we evaluated suitable substitutes compatible with the NPV of O. pseudotsugata . Materials tested included two lignosulfonates, a disulfobenzophenone, and two fluorescent whitening agents. Shade was also tested as a reference standard. The materials were evaluated by exposing virus-absorber mixtures to UV radiation from high-intensity mercury sun lamps. We used a new technique that permitted individual handling of samples, on sterile disposable Teflon pads, through various steps of the test procedure. Two of the materials, Tinopal DCS (a stilbene fluorescent whitening agent) and Raymix powder (a lignosulfonate), protected O. pseudotsugata NPV against UV radiation equally or better than did Shade. Both UV absorbers are soluble in cold water, with pH near neutrality.