IMPACT OF SOIL APPLICATIONS OF BEAUVERIA-BASSIANA AND MARIANNAEA SP ON NONTARGET FOREST ARTHROPODS

Replicated plots were established in pear thrips-infested sugar maple stands. They were treated with Beauveria bassiana as an emulsifiable c oncentrate and a nutrient-based granular formulation and with Marianna ea sp. as a wettable powder. Postapplication invertebrates moving acro ss plots were collected daily for 10 days in pitfall traps. Collected individuals were identified, held for 10 days, and then evaluated for the presence of fungal infection and other potential pathogenic microo rganisms. A total of 3615 invertebrates were collected and identified. Of the invertebrate population in treated plots that fell into pitfal l traps, 2.8% became infected with either B. bassiana or Mariannaea sp . The fungi applied also occur naturally in sugar maple forest soils; therefore, it was impossible to confirm whether the infection we obser ved in treated plots was a result of contact with the spores we applie d. Because we obtained infection among invertebrates collected from co ntrol plots, it is likely that these fungi do attack invertebrates und er natural forest conditions. Of the 2584 invertebrates examined furth er for obligate internal pathogens, 2.5% were infected with entomophth oralean fungi, protozoans, and/or nematodes. Results suggest that B. b assiana and Mariannaea sp. could be applied to forest soil without a s ignificant negative impact on the forest-dwelling invertebrate populat ion. (C) 1997 Academic Press.