|LINN, JR., CHARLES|
Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2002
Publication Date: 2/1/2003
Citation: Nofima, S., Linn, C.J., Morris, B., Zhang, A., Roelofs, W. 2003 Identification of host fruit volatiles from hawthorn (Crataegus spp.) attractive to hawthorn-origin Rhagoletis pomonella flies. Journal of Chemical Ecology. 29(2):321-336.
Interpretive Summary: The apple maggot fly is the primary pest of apple, with wormy fruit in unsprayed orchards often reaching 100 per cent. This insect occurs in North America as two races, one on introduced apple, and one on native hawthorn. In earlier work, flies from apple were shown to be attracted to synthetic compounds isolated from apples. Flies reared from hawthorn were not effectively attracted to the artificial apple odor blend. Flies reared from hawthorn were attracted to a synthetic blend isolated from hawthorn fruit, which is different from the volatile blend identified from apple. This study has confirmed that differences in host plant preference play an important role in reproductively isolating the fly host races from apple and hawthorn. This information is of theoretical interest to scientists because it verifies how insects can become pests by shifting from native host plants to agriculturally important host plants. In addition, this information is of practical importance because traps baited with selected host orders should be useful to commercial growers as a monitoring tool to indicate when control actions, such as spraying insecticide, need to be initiated.
Technical Abstract: Solid-phase microextraction (SPME) and gas chromatography coupled with electroantennaographic detection (GC-EAD) were used to identify volatiles compounds from hawthorn fruit (Crataegus spp.) acting as behavioral attractants for hawthorn-infesting Rhagoletis pomonella files. Constant EAD activity was obtained from six chemicals: ethyl acetate (94.3%), 3-methylbutan-1-ol (4.0%), isoamyl acetate (1.5%), 4,8-dimethyl-1,3(E),7-nonatriene (0.07%), butyl hexanoate (0.01%), and dihydro-b-ionone (0.10%). In a flight-tunnel bioassay, there was a dose-related increase in the percentage of flies flying upwind to the six-component mixture. Hawthorn-origin flies also made equivalent levels of upwind flight with the synthetic blend and an adsorbent extract of volatiles collected from whole fruit, each containing the same amount of the 3-methylbutan-1-ol compound. Significantly lower levels of upwind flight occurred to a previously identified volatiles blend of ester compounds that attracts R. pomonella flies infesting domestic apples, compared with the hawthorn volatile mix. Selected subtraction assay showed further that the four-component mixture of 3-methylbuta-1-ol, 4,8-dimethyl-1,3(E),7-nonatriene, butyl hexanoate, and dihydro-b-ionone also elicited levels of upwind flight equivalent to the six-component mix. Removal of 3-methylbutan-1-ol from the four-component blend resulted in complete loss of upwind flight behavior. Removal of dihydro-b-ionone, 4,8-dimethyl-1,3(E),7-nonatriene, or butyl hexanoate from the four-component mixture resulted in significant decreases in the mean number of upwind flights compare to the four-or six-component mixtures.