2008 Annual Report
1a.Objectives (from AD-416)
Expeditiously identify chemical attractants (e.g., pheromones and plant
volatiles) for agriculturally important insect species (either pests or
biocontrol agents for weed or insect pests) for which such knowledge is
lacking or incomplete, determine the biological and environmental
parameters for natural emission of the compounds, and synthesize or
otherwise obtain them in quantities sufficient for field use. Characterize the behavioral responses toward the identified compounds under field conditions, with special consideration to the development of practical management tools.
1b.Approach (from AD-416)
Seek pheromones and host-plant related attractants for selected insect species. Species studied will include, but not be limited to, Diorhabda elongata (a biocontrol agent of saltcedar), Galerucella calmariensis (a biocontrol agent of purple loosestrife), and various flea beetle species (including vegetable crop pests and also biocontrol agents of leafy spurge). Collect volatiles from male and female insects and from host plants and analyze these by gas chromatography, mass spectrometry, and electrophysiology (“electroantennograms”). Those compounds that are emitted by just one sex and that are detected with great sensitivity by the insect antennae are likely to be pheromone components. Similarly, host plant compounds with high antennal sensitivity are potential attractants. Identify the structures of these key compounds using mass spectrometry, nuclear magnetic resonance spectroscopy, chemical tests, and other appropriate methods. Synthesize the compounds using the methods of organic chemistry or otherwise obtain them in bulk from botanical or other sources. Use techniques such as “sticky traps” or other trapping methods to evaluate the attractiveness of synthetic compounds under field conditions, relative to controls and also to live insects. Characterize the behavior toward the attractants under laboratory conditions, if possible. Develop the newly identified attractants as practical insect management tools, for monitoring or manipulating populations of the insects under consideration. For key pheromones, such as those of nitidulid beetles, develop new synthetic schemes suitable for commercial pheromone production.
Research during fiscal year 2008 was concentrated in three areas: emerald ash borer attractants, improved synthesis of Galerucella beetle pheromone, and lesser mealworm beetle pheromone. Work continued on attractants for the emerald ash borer (Agrilus planipennis, "EAB"), a severe invasive pest from Asia, considering both beetle-produced and host-plant-related compounds. Using electrophysiological techniques, EAB antennae were found to be especially sensitive to two compounds (both sesquiterpenes) present in ash bark in trace amounts, suggesting the compounds could be important attractants. Chemical analysis and literature search revealed that one compound, 7-epi-sesquithujene, was previously known from ash, but the other, identified as (-)-eremophilene, was not. The compounds are not commercially available, but progress was made in obtaining them in quantities suitable for field trials by purification from plant oils (e.g., sandalwood, manuka, phoebe), either directly or following chemical modification of the oil. Goals are to acquire amounts sufficient for field testing and to evaluate whether they can be effective baits in traps for beetle detection, alone or in blends. In field tests, neither these plant compounds nor the previously identified, putative EAB pheromone, was demonstrably attractive when placed in traps at convenient heights (1-2 m). Future tests will assess attractiveness high in ash trees, where most EAB flight activity occurs. This research addresses NP 304, Component 4.
An improved method was devised for synthesizing the aggregation pheromone of Galerucella beetles (a biological control agent for purple loosestrife). The synthesis of this rather complicated compound was reduced from 13 to 10 steps, and the overall yield was increased sixfold. The pheromone has good potential for use in the purple loosestrife biological control program by scientists and land managers, and the new synthesis can make the pheromone more easily available. This research addresses NP 304, Component 9.
Finally, pheromone research continued on the lesser mealworm beetle (Alphitobius diaperinus). Five male-specific compounds were identified, including trans-beta-ocimene, (R)-(+)-limonene, (S)-(+)-linalool), (R)-(+)-daucene), and 2-nonanone. These compounds are obtainable commercially or by straightforward synthesis. The beetles are long-lived, and males were found to emit the compounds for as long as a year, ceasing when conditions became unfavorable (e.g., lack of food) and resuming again when conditions were corrected. The beetles seldom fly, and a pit-fall type trap was developed for assessing attraction of walking beetles. Traps with the synthetic compounds were significantly more attractive than unbaited traps at an infested, commercial turkey operation. This research addresses NP 304, Component 2.
ASH-BARK COMPOUND FOR EMERALD ASH BORER. Compounds from ash bark were evaluated as possible attractants for the emerald ash borer (Agrilus planipennis), a tree killing, invasive beetle pest from Asia. Compounds in the complex blend from ash bark that were sensed particularly well by beetle antennae, based on electrophysiological analysis ("electroantennograms"), were considered to have good potential as attractants. One especially active compound, present at a very low level, was previously unidentified from ash and was determined to be (-)-eremophilene. Chemical methods were developed to obtain enough (-)-eremophilene for field testing from oils of other plants. This compound may prove to be important as part of an attractive blend for baiting traps to detect new infestations of these beetles. This research addresses NP 304, Component 4, Problem Area 4d.
NEW SYNTHETIC METHOD FOR GALERUCELLA PHEROMONE. An improved synthetic method was developed for the pheromone of Galerucella beetles. These beetles are important biological control agents of the invasive wetland weed, purple loosestrife. The pheromone is fairly complex, containing furan and lactone ring structures. The synthesis was reduced from 13 to 10 steps and the yield was increased sixfold. The pheromone has good potential for use by scientists and land managers in the purple loosestrife biological control program, to monitor or manipulate beetle populations, and the new synthesis can make the pheromone more readily available. This research addresses NP 304, Component 9, Problem Area 9c.
PHEROMONE FOR THE LESSER MEALWORM BEETLE. A male-produced pheromone was identified in the lesser mealworm beetle (Alphitobius diaperinus), a cosmopolitan and abundant pest in poultry houses and stored grains. The male-specific blend consists of five compounds, including three terpenes, a sesquiterpene, and a ketone, which are commercially available or readily synthesized. A blend of the five compounds was shown to be attractive in experiments at a turkey-production facility. Pheromones have become useful tools for managing or detecting a wide variety of insect pests, and one is now known for the lesser mealworm. This research addresses NP 304, Component 2, Problem Area 2a.
5.Significant Activities that Support Special Target Populations
|Number of Non-Peer Reviewed Presentations and Proceedings||1|
Petroski, R.J. 2007. Facile biphasic deprotection of aldehyde dimethylhydrazones with aqueous hydrochloric acid. Letters in Organic Chemistry. 4:452-455.
Petroski, R.J. 2007. New phosphonate reagents for aldehyde homologation. Synthetic Communications. 37(21):3841-3854.
Zilkowski, B.W., Bartelt, R.J., Vermillion, K. 2008. Analysis of 2,4,6-nonatrienal geometrical isomers from male flea beetles, Epitrix hirtipennis and E. fuscula. Journal of Agricultural and Food Chemistry. 56(13):4982-4986.