2011 Annual Report
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)
Approaches to insect management 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 Bacillus thuringiensis) 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.
Progress was made in identifying pheromones of several important stink bug pests, which will allow improved monitoring and management in vegetable and other crops. For brown marmorated stink bug, the existence of an aggregation pheromone was verified, suspected pheromone components synthesized, and significant numbers of adults were attracted to traps baited with various combinations of synthetics in the field (in Beltsville, MD, and by ARS Kearneysville, WVA). For the tomato and vegetable bug pest, Arvelius albopunctatus, two male-specific compounds were isolated and partially characterized; female antennae are sensitive to the compounds, indicating they are likely the pheromones. For harlequin bug, a colony has been established and initial field testing of candidate lures undertaken.
Progress was made with systems to conserve and augment key beneficial predator insects. An attractant to multiple insect predators, including lacewings and predatory stinkbugs was studied with a commercial partner and a lure is bing commercialized. Also, a suspected sex pheromone of the native insect predator “wheel bug”, Arilus cristatus, was isolated, chemically identified, and is being tested in the field.
We have identified potentially effective microbial controls for key pests of small farms and gardens. Using the IIBBL insect virus collection, we identified and characterized baculovirus samples that infect the cabbage looper, a key vegetable caterpillar pest. In bioassays, a baculovirus isolate originally identified from diamondback moth (also a cole crop pest) was found to kill cabbage looper larvae significantly faster than the other viruses we tested. Bioassays of all 23 isolates are underway. For development of Bacillus thuringiensis (Bt) strains, which are sustainable biological controls in vegetables, we found that Bt strains grow more slowly on cabbage leaf extract probably because the slight acidity does not allow good competition with naturally occurring microbes. This may point to use of specific cultivars and/or formulations which alter conditions in favor of Bt survival on leaf surfaces.
We have made progress in determining the genetic basis of plant defense mechanisms of cole crops. Using microarray technology, selection of genes involved in plant response to diamondback moth is underway in Arabidopsis, a plant related to commercial cole crops. Preliminary results show Arabidopsis lines differ in their resistance to diamondback moth, which will allow bioassays of Arabidopsis plants altered in specific candidate genes. These results will be used to tie broccoli genes to diamondback moth resistance, for eventual use in commercial varieties.