INFLUENCE OF DROPLET SIZE, SOLAR ULTRAVIOLET-LIGHT AND PROTECTANTS, AND OTHER FACTORS ON THE EFFICACY OF BACULOVIRUS SPRAYS AGAINST PANOLIS-FLAMMEA (SCHIFF) (LEPIDOPTERA, NOCTUIDAE)

Protectants aimed at reducing the effect of solar ultraviolet light were formulated with nuclear polyhedrosis virus sprays used against pine beauty moth (Panolis flammea (Schiff.)) in Scottish forests and evaluated in a field trial and by a bioassay. Trees c. 2 m high were sprayed at ultra-low volume using two droplet sizes, on two occasions. Test formulations included virus with egg albumen on its own or with Tinopal, lignosulphonate or riboflavin, and virus with an emulsified mineral oil, Actipron. Ultraviolet light was measured by radiometer and polysulphone film. Larvae were monitored day-to-day in the bioassay and after gathering field samples, until most infected larvae had died. Infection levels were significantly affected by spray droplet size, and exposure before ingestion. Small droplet sprays led to higher infection levels than large droplet sprays. Infectivity declined on exposure to weather. Infection levels on the larger trees were lower than on small ones. The different formulations performed in a similar way, whether exposed or not; the three protectants added to the spray conferred no obvious benefit at the concentrations used. © 1990.