2012 Annual Report
1a.Objectives (from AD-416):
1: Characterize fungal strains associated with insects (including insect pathogens and symbionts and plant pathogens vectored by insects) and develop methods to enable their rapid identification and tracking.
1a. Develop molecular assays to detect and quantify plant pathogenic oomycetes vectored by insects to verify transmission.
1b. Identify the primary fungal symbiont associated with Asian ambrosia beetles and assess the genetic diversity of these fungi from beetles in the eastern United States.
1c. Evaluate fungal delivery, establishment and persistence in target populations of invasive wood-boring beetles.
2: Determine and improve the effectiveness of fungi for use within integrated management systems for greenhouse, horticultural and landscape pests, including but not restricted to thrips, whiteflies, ambrosia beetles and emerald ash borer.
2a. Develop a biologically-based IPM program for western flower thrips infesting greenhouse crops.
2b. Compare the efficacy of Beauveria bassiana and Metarhizium anisopliae against the Q biotype of Bemesia tabaci.
2c. Develop available microbial control agents for management of Asian ambrosia beetles and their symbiotic fungi.
2d. Integrate pathogenic fungi with other biocontrol agents for emerald ash borer and evaluate non-target impacts.
1b.Approach (from AD-416):
The goals of this project are to integrate entomopathogenic fungi into management systems for selected insect pests of horticultural, nursery and landscape plants and to track fungal strains in these environments. The work comprises fundamental laboratory studies as well as applied greenhouse and field research. This project will develop basic information on the biology of fungal and oomycete pathogens associated with insects, their genetic and phenotypic variability, and their survival and transmission in greenhouse and field environments. Integration of fungal pathogens will be accomplished for management of key pests: a biologically based program will combine use of pathogens and predators for control of western flower thrips infesting greenhouse crops; efficacy of fungal pathogens will be determined for Bemisia whiteflies (B. tabaci Q biotype); microbial control agents will be developed for management of Asian ambrosia beetles; and a fungal mycoinsecticide will be integrated with other biocontrol agents used against emerald ash borer. Fungi used in the ways developed in this project will provide safe, effective biological alternatives to synthetic chemical insecticides and/or rotational partners for insecticide resistance management.
Laboratory bioassays were conducted to test the virulence of commercial strains of insect pathogenic fungi against the granulate ambrosia beetle, Xylosandrus crassiusculus. Among the three strains tested, Beauveria bassiana Naturalis and Metarhizium brunneum F52 were more virulent than B. bassiana GHA. A complementary study is currently underway to determine female foundress survival and brood production in beech twigs sprayed with the same fungi. In addition, a biocontrol product based on the fungal antagonist Trichoderma harzianum is being tested for its effect on the beetle’s fungal symbiont.
Three parasitoids of emerald ash borer were released at multiple sites within two emerald ash borer infested areas in New York. A cluster of girdled trees was established at each of eight sites to help focus beetle attacks and facilitate parasitoid searching. Half of the sites were treated to test provision of supplemental nectar resources for parasitoid adults. Yellow pan traps were placed on trees to monitor for adult parasitoids of subsequent generations. Tree felling and peeling to quantify parasitism will be done in early 2013. In another experiment, woodpecker predation was quantified in relation to emerald ash borer density. Overall predation was 33 percent and the amount of predation was positively correlated with emerald ash borer density.
Field efficacy of insect pathogenic fungus against Asian ambrosia beetle. Field assays were done by ARS researchers at Ithaca, New York to test the efficacy of commercial formulations of fungal biocontrol agents against Xylosandrus germanus. Small logs attached to stakes were placed in infested woodlots and sprayed with a commercial strain of Metarhizium brunneum. Beetle attack rate was significantly reduced versus controls. Survival of foundress females was reduced to 38 percent versus 79 percent in controls. Only 56 percent of galleries on treated logs had progeny present versus 90% for controls. Infection of adults, larvae and pupae by M. brunneum was evident with galleries. These results indicate the potential utility of this biopesticide for managing Asian ambrosia beetles.
Critical factors in the efficacy of thrips biocontrol agents identified. Highly virulent insect pathogenic fungi identified in laboratory bioassays against western flower thrips (WFT) provide inconsistent control of this pest in greenhouse trials. The reasons for this are not completely understood. In a series of greenhouse tests, ARS researchers at Ithaca, New York assessed the efficacy of foliar applications of two commercially available fungi, Beauveria bassiana strain GHA and Metarhizium brunneum strain F52, against WFT on potted impatiens. Under optimal conditions, the two fungi produced similar levels of control (76–82%). Control was slow to develop, coinciding with plant growth to the point of canopy closure, and highly dependent upon ambient moisture conditions, with tests revealing a near-perfect correlation between thrips control and daily hours of high relative humidity. Control was reduced, regardless of humidity or plant age, when plots were exposed to constant ventilation. In light of these findings, the thrips-control efficacy of fungi can be expected to vary markedly with many aspects of crop culture, including humidity, plant age (size), and plant location relative to air circulation within a greenhouse.
Detection and control of Phytophthora cryptogea and P. drechsleri: two pathogens of ornamental crops. Even though Phytophthora cryptogea and P. drechsleri have been described for over 90 years in ornamental crops, identifying these two species has been problematic. Researchers at NC State University in Raleigh, in collaboration with ARS researchers at Ithaca New York, have determined that P. cryptogea and P. drechsleri are sister species that are continuing to diverge based on DNA sequence analysis, and that carry-over of the pathogens was more important than new introductions as a cause of epidemics, emphasizing the importance of sanitation practices. Over three years of trials, the fungicides fluopicolide, fenamidone, and ametoctradin + dimethomorph were consistently effective in disease control when applied as drenches on a 14-day schedule, whereas cyazofamid and dimethomorph treatments always produced root rot rating less than the controls. Because the effective fungicides have different modes of action, growers have valuable rotation options for managing Phytophthora root rot and avoiding pathogen resistance in Phytophthora populations.
Managing emerald ash borer infestation. The extent of an emerald ash borer infestation in western New York was determined by ARS researchers at Ithaca, New York using more than 100 individual (sentinel) girdled ash trees located up to 10 km away from the likely center of the infestation. Clusters of girdled ash trees were established near the center to act as sinks to attract potentially dispersing beetles. Trees were felled and peeled to quantify infestation rate. Twelve sentinel trees contained emerald ash borer larvae leading to an estimate of infestation area of 48 square km. Trees within clusters were more heavily infested (9 larvae per square meter of bark) than sentinel trees or ungirdled trees. This indicates that clusters of girdled trap trees that are destroyed prior to the following season can help lower local densities of emerald ash borer.
Faria, M., Hotchkiss, J.H., Wraight, S.P. 2011. Application of modified atmosphere packaging (gas flushing and active packaging) for extending the shelf life of Beauveria bassiana conidia at high temperatures. Biological Control. 61:78-88.
Braun, S.E., Sanderson, J.P., Wraight, S.P. 2012. Larval Bradysia impatiens (Diptera: Sciaridae) potential for vectoring Pythium root rot pathogens. Environmental Entomology. 102:283-289.
Jandricic, S.E., Wraight, S.P., Bennett, K.C., Sanderson, J.P. 2010. Developmental times and life table statistics of Aulacorthum solani (Hemiptera: Aphididae) at six constant temperatures, with recommendations on the application of temperature-dependent development models. Environmental Entomology. 39(5):1631-1642.
Ugine, T.A., Sensenback, E.J., Sanderson, J.P., Wraight, S.P. 2010. Biology and feeding requirements larval hunter flies Coenosia attenuata (Diptera:Muscidae) reared in larvae of the fungus gnat Bradysia impatiens (Diptera:Sciaridae). Journal of Economic Entomology. 103(4):1149-1158.