In some cases, the plant an insect pest lives on influences the ability of some natural enemies to control it. The fungus Paecilomyces fumosoroseus was shown to be highly efficacious against greenhouse whitefly on cucumber, but less effective against the same insect species on tomato. Does the crop also affect the efficacy of the fungus against silverleaf whitefly?
Greenhouse experiments were conducted on cucumber, cabbage and tomato to test their effects on the susceptibility of whitefly nymphs to the Pfr 97 strain of the fungus. Nymphal mortality was more than 70%, and whenever conditions were favorable, there was a high percentage of sporulation on the cadavers. There was no significant influence of the host vegetable species on nymphal mortality at either 7 or 14 days after treatment. Fungal sporulation on the surface of cadavers and spore viability was not different on the various vegetables either. Similar results were obtained in other tests comparing three tomato cultivars.
Many factors, such as the whitefly species, the cultivars, the quality of fungal inoculum, the method of spraying, and the climatic conditions during the trials can affect the efficacy of fungal pathogens. In these experiments the effectiveness of the fungus was not affected by the host plants tested, suggesting that P. fumosoroseus is adaptable for use in controlling silverleaf whitefly at least on cabbage, cucumber and some tomato cultivars, if not on many other plants as well.
Vidal, C., L. S. Osborne, L. A. Lacey, and J. Fargues. 1998. Effect of host plant on the potential of Paecilomyces fumosoroseus for controlling the silverleaf whitefly, Bemisia argentifolii in greenhouses. Biol. Control. 12: 191-199.
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