DIFFERENTIAL SPORE PRODUCTION BY BOTRYTIS-CINEREA ON AGAR MEDIUM AND PLANT-TISSUE UNDER NEAR-ULTRAVIOLET LIGHT-ABSORBING POLYETHYLENE FILM

Plastic films containing additives that alter their transmission of th e light spectrum may be useful tools for the control of aerial plant p athogens of greenhouse crops. Several samples of polyethylene films co ntaining additives that absorb near ultraviolet (nUV) light in the ran ge 280 to 380 nm were compared for their ability to affect spore germi nation, mycelial growth, and sporulation of Botrytis cinerea on agar m edium. One film was selected and further evaluated. The kinetics of sp ore production by the pathogen was similar on agar medium and on tomat o stem tissue, and whether incubation took place under the nUV-absorbi ng film or under a control film. However, spore production on both typ es of substrates under the nUV film remained at less than 0.05% that o f the control for several weeks after inoculation, demonstrating that the nUV film inhibited rather than delayed sporulation. A sharp reduct ion of spore production was also observed on other plant tissues. Howe ver, the efficiency of the nUV film appeared different for different p lants, and it was lower on flowers and cotyledons than on stem tissue. Two of the five strains of B. cinerea tested on tomato stem tissue we re less sensitive to sporulation inhibition by the nUV film. To clarif y the potential of nUV films for the control of gray mold on greenhous e crops, the epidemiological significance of these results needs to be further examined in light of the abundance of such strains in the env ironment.