2011 Annual Report
1a.Objectives (from AD-416)
The goal of this project is to develop innovative and sustainable technologies to manage insect pests and their natural enemies to reduce damage to trees, shrubs, and flowering perennial plants in managed and unmanaged urban landscapes. Lepidopteran and coleopteran pests are the principal defoliators in urban landscapes and nearby forests, and constitute 60% of recorded invasive insect species in North America. The research focuses on five of the most destructive lepidopteran and coleopteran pests in urban landscapes: gypsy moth, winter moth, and dogwood borer; and emerald ash borer and Asiatic garden beetle; however, research results are expected to be broadly applicable to other urban landscape insect pests. The research is organized around three objectives: (1) identify and synthesize plant-derived semiochemicals and insect pheromones attractive to pests, and design insect monitoring and management strategies employing them; (2) develop microbial and arthropod natural enemies as biocontrol agents of native and exotic pests of landscape plants; and (3) identify at the molecular level genes and gene pathways critical for success of landscape pests; employ molecular technologies to determine the role of host pathways targeted by entomopathogens; and target these pathways with natural or molecular biopesticides to kill pests.
1b.Approach (from AD-416)
This highly interdisciplinary project combines concepts and methodologies from analytical and synthetic organic chemistry, insect chemical behavior, insect pest-pathogen genomics, and microbial and insect ecology to develop strategies to combat urban landscape pests. Plant-derived semiochemicals and insect pheromones will be identified, and novel chemical and biological syntheses will be devised to enable their use for monitoring pest populations, disrupting pest reproduction, and luring pests into traps to be exposed to pathogenic microorganisms. Ecological attributes of pathogens underlying virulence, specificity, and accessibility to hosts will be determined. Transcriptome analysis of gypsy moth larvae challenged with various classes of pathogens will expose insect molecular vulnerabilities exploited by virulent pathogens. Naturally occurring pathogens best able to exploit these vulnerabilities will be applied directly to the environment, or placed in traps with species-specific semiochemicals to lure pests into contact with the pathogens to initiate epizootics. Experimental native and exotic assemblages of woody and herbaceous urban landscape plants will be characterized according to the natural enemy resources that they provide, and tested for their ability to support natural enemies and thereby to promote effective biocontrol of urban landscape pests.
IIBBL scientists addressed the first project objective, “Identify and synthesize plant-derived semiochemicals and insect pheromones attractive to pests” by developing a conventional chemical synthesis for 7-epi-sesquithujene, a plant volatile attractive to emerald ash borer (EAB), Agrilus planipennis. EAB is an invasive Asian pest that threatens all native ash (Fraxinus) species. Effective long-distance volatile attractants have been needed to develop a trapping system for this pest and as a monitoring tool. In a parallel effort to produce this compound in an in-vitro cell culture system, we succeeded in producing an enzyme essential for its synthesis, the terpene synthase TPS4, in bacteria.
IIBBL scientists addressed the second project objective, “Develop microbial and arthropod natural enemies as biocontrol agents of insect pests of landscape plants” by determining the genetic relatedness of soil bacterium Bacillus thuringiensis (Bt) bacterial strains chosen to include diverse combinations of biochemical traits, using multi-locus sequence typing. The soil bacterium Bt has been an important biocontrol agent for moth pests and determining the habitat-specificities of different varieties was crucial for the selection of Bts with improved persistence in urban landscapes. Results indicated that most soil Bts belong to a relatively few dominant groups.
IIBBL scientists addressed the third project objective, “Identify genes and gene pathways critical for success of pests; employ molecular technologies to determine the role of host pathways targeted by entomopathogens; and target these pathways to kill pests” through conducting new transcriptomic studies of caterpillar responses to pathogen infection. New biological controls are needed for the gypsy moth (Lymantria dispar), the most serious woody landscape pest in the U.S. In order to determine molecular vulnerabilities of gypsy moth to pathogens and parasites, we initiated transcriptome studies to identify expressed genes in a cultured cell line and in specific larval tissues. Larval tissues were also infected with the microbial pathogen Bt or parasitized by the braconid parasitoid wasp Glyptapanteles indiensis to evaluate the pest gene differential regulation. We also demonstrated the ability of DNA from G. indiensis parasitoid wasp polydnavirus to integrate into DNA of gypsy moth larvae.
Absolute configuration and synthesis of 7-epi-sesquithujene. Emerald ash borer (EAB), Agrilus planipennis, is an invasive Asian pest that threatens all native ash tree (Fraxinus) species. One promising candidate attractant for this pest, the plant volatile 7-epi-sesquithujene, gives positive neurophysiological responses in olfactory pathways of both male and female EAB. We determined the spatial arrangement of atoms of 7-epi-sesquithujene, which is necessary for its effective and economical synthesis. The attractiveness of the synthetic product to EAB is being studied under field conditions. This will enable use of effective long-distance volatile attractants in a trapping system as a monitoring tool for EAB.
Khrimian, A., Cosse, A.A., Crook, D.J. 2011. Absolute configuration of 7-epi-sesquithujene. Journal of Natural Products. 74(6):1414-1420.
Blackburn, M.B., Martin, P.A., Kuhar, D.J., Farrar, R.R., Gundersen, D.E. 2011. The occurrence of Photorhabdus-like toxin complexes in Bacillus thuringiensis. PLoS One. 6(3):e18122.