Location: Emerging Pests and Pathogens Research2011 Annual Report
1a. Objectives (from AD-416)
Develop the potential of entomopathogenic fungi to manage pear thrips, western flower thrips and other major insect pests with soil-dwelling stages, and to encourage the implementation of fungus-based biocontrol methods as part of total IPM approaches for use greenhouse and forest environments against these pests.
1b. Approach (from AD-416)
Utilize entomopathogenic fungi from the University of Vermont (UVM) collection, the ARS Collection of Entomopathogenic Fungal Cultures (ARSEF; Ithaca, NY), and newly isolated strains from greenhouse and field studies to develop improved methods for the use of these fungi in practical programs for the integrated pesticidal and biological control of soil-dwelling stages of western flower thrips and other major insect pests in greenhouses as well as of pear thrips affecting sugar maple trees. The isolation and preservation of new fungal germplasm and co-deposition of old and new UVM isolates in ARSEF remain a major activity. Development of new or improved means and formulations to deliver fungal entomopathogens to control soil-dwelling stages of thrips and other insects in greenhouses is a major concern. Improving the ability of fungal control agents to resist drought and high temperatures with a balanced set of modified formulations and applications approaches is critically important.
3. Progress Report
Pear thrips populations were monitored and found to be stable at low to moderate levels in Vermont in Spring 2011. During the summer of 2010, moderate damage (mostly due to a May 2010 killing frost that defoliated hundreds of acres of sugar maples) was seen in some Vermont counties. Damage to maples from thrips damage was light on refoliating trees in June 2010 and still relatively low in June 2011. A total of 194 isolates were transferred from the UVM Collection of Entomopathogenic Fungi to ARS Collection of Entomopathogenic Fungal Cultures. A total to 743 fungal isolates from thrips or other arthropods were transferred to ARSEF from Sept 2008 to June 2011. Investigations continued on the natural distribution of entomopathogenic fungi among pear thrips populations in maple forest soils. From soil samples from maple forest stands in several counties of New York, Vermont and New Hampshire,153 fungal isolates were obtained from pear thrips and 24 cultures from other arthropods. The fungi from thrips included Beauveria bassiana (12 isolates), Metarhizium anisopliae (3 isolates), Lecanicillium sp. (63 isolates), Mariannaea sp. (10 isolates), Paecilomyces sp. (7 isolates), Paecilomyces lilacinus (2 isolates), Isaria sp. (41 isolates), Conidiobolus (2 isolates), and a Hirsutella (2 isolates). Research was conducted to assess novel means to produce fungi that tolerate high heat. Specifically, apparent hyphal fusions between two morphologically different B. bassiana isolates resulted in a presumptive heterokaryotic colony that produced notably thermotolerant conidia. Higher densities of longer hyphal tip growth were observed in the co-incubation of the two isolates than the individual cultures. After three cycles of the co-incubation, the culture was exposed to 45°C and then re-streaked on SDAY/4 to select thermotolerant colonies. Two dominant colonies whose morphologies differed significantly from the parental colonies were selected after cycling and heat exposure. One colony showed higher thermotolerance than the parental strains, had sponge-like mycelial growth, and produced darker conidia (that might indicate an accumulation of more intracellular materials related to thermotolerance); the parental colonies had flat mycelial growth and lighter-colored conidia. A bioassay of this heat-treated isolate against western flower thrips, Frankliniella occidentalis, indicated that the derived colony’s virulence to the thrips did not differ from the parental strains. Monitoring of activities has been conducted by email, face-to-face meetings, and phone calls between the ADODR and the cooperator.