1a. Objectives (from AD-416):
This project has the long-term objective to develop and improve diverse biologically based controls for insects in vegetable crops for urban small farms and gardens, considering both organic and non-organic production. Research will target insect pests that cause major damage to several of the most common crops in small vegetable farms and gardens in urban settings, and for which there is potential to shift from synthetic chemical control strategies to bio-based strategies. The main focus will be pests of cole crops, cucurbits, and vegetable seeds and seedlings, although other important crops may receive attention for specific problems. The specific objectives are to: (1) Identify, synthesize (including in vitro biosynthesis) and evaluate semiochemicals to manage significant insect pests of small farms and gardens; (2) Discover and develop systems to conserve and augment key natural enemies of small farms and gardens, using pheromones and other attractants, specially-adapted crop cultivars, and food provisioning through plant and supplemental sources; (3) Identify effective microbial controls for key pests of small farms and gardens, including discovery of molecular and ecological mechanisms for sustained field reproduction and persistence, using Bt, baculoviruses, and other entomopathogens; (4) Determine genetic basis of plant defense mechanisms of high-value crops of small farms or gardens (such as cole crops) against destructive insects, including pest aversion and resistance; and (5) Develop predictive tools for measurement of pest suppression and damage for evaluation of farm and garden habitats.
1b. Approach (from AD-416):
The project brings together a research team with diverse expertise for multiple approaches to insect management. Those approaches will include discovery, commercially-viable synthesis, and deployment of natural insect attractants for harlequin bug, brown marmorated stink bug, other pestiferous true bugs, and striped cucumber beetle, using electrophysiology and diverse cutting-edge chemical diagnostic methods, multipronged methods of chemical and in vitro sythesis, formulation development, and investigation of insect behavioral response in the field. Conservation and augmentation of generalist predators (including predatory stink bugs and lacewings) will use existing and discovered male-produced aggregation pheromones, coupled with new approaches to assessing biological control impact on important vegetable pests. Pest-specific microbial controls will be targeted to identify and evaluate bacterial strains (particularly Bt) which can survive and colonize crops under field conditions, and baculoviruses which are efficacious against key vegetable pests. Plant resistance investigations for cole crops will take an innovative approach using molecular-based gene discovery. The combination of semiochemical and biological controls, including microbial controls, and crop resistance, will offer a range of non-chemical tactics useful to a bio-based integrated pest management strategy for major vegetable pests in urban small farms and gardens.
3. Progress Report:
To address our first objective, we have made substantial and exciting progress on stink bug behavioral chemical identification, synthesis, and evaluation, particularly on brown marmorated stink bug (BMSB) and harlequin bug, which are newly invasive and established invasive major pests, respectively. For BMSB, a provisional patent was filed in December 2011. A repellent of BMSB has also been discovered, with a patent claim pending. We expect ongoing field evaluations for both species to result in significant tools for monitoring and management, available next year to affected growers and homeowners pending commercialization. Progress with other true bugs has been delayed in favor of concentrating particularly on the urgent problem of BMSB, and because of the retirement of our stink-bug research scientist in December 2011. Targeting of the cucumber beetles, particularly the striped cucumber beetle, continues on both conventional chiral synthesis and in vitro biosythesis tracks. To address our third objective, we identified pathogens of seedling pests including characterization of baculoviruses in 2 key seedling pests. Bioassays of 20 clonal isolates of black cutworm baculovirus derived from a field virus isolate indicated potential for selection of isolates with more rapid mortality. A new baculovirus attacking true armyworm was identified from Kentucky pastures; DNA analysis of this and other baculoviruses in the IIBBL collection revealed at least 3 distinct baculoviruses attacking true armyworm. We have also identified strains of Bacillus thuringiensis (Bt) expected to be toxic against seed corn maggot, another target seedling pest. A variety of Bt’s are being testing for their ability to grow and persist on cabbage; over 200 Bt isolates have been both phenotypically and phylogenetically characterized. This thorough characterization process, including the fullest possible genetic diversity of Bt, is critical to discovering true biological controls for target cole crop pests. To address our fourth objective, we examined the genetic basis of cole crop defenses against the target key pest diamondback moth being studied in the model plant Arabidopsis. We successfully created an Arabidopsis line that over-expresses a diamondback moth infestation inducible transcription factor (OEEV47). Transcription factors regulate numerous genes involved in a multigene response; an infestation inducible transcription factor may be crucial in conferring resistance to the insect. Using OEEV47, genes responsive to this transcription factor have been identified using an Arabidopsis complete genome microarray chip via an interagency agreement with National Cancer Institute. Secondly, environmental factors affecting the expression of this transcription factor have been assessed to help determine if expression of the transcription factor occurs due to factors other than infestation. Together, this information helps to determine what genes are crucial for resistance to diamondback moth.
1. Discovery of true pheromone of brown marmorated stink bug. ARS researchers in Beltsville, MD and Kearneysville, WV have discovered the true pheromone of brown marmorated stink bug, an invasive insect pest attacking fruit and vegetables and infesting structures in over 40 U.S. states. Male bugs emit an aggregation pheromone, which attracts both sexes of adults and nymphs and is described in a provisional patent filed on 12/16/2011. Researchers are continuing to undertake intensive field and laboratory evaluations of pheromone formulations and traps based on identification and synthesis achieved. We expect ongoing field evaluations to result in significant tools for monitoring and management, available next year to affected growers and homeowners pending commercialization.
Harrison, R.L., Popham, H.J., Breitenbach, J.E., Rowley, D.L. 2012. Genetic variation and virulence of Autographa californica multiple nucleopolyhedrovirus and Trichoplusia ni single nucleopolyhedrovirus isolates. Journal of Invertebrate Pathology. 110(1):33-47.