ARS | Publication request: Field Capture of Northern and Western Corn Rootworm Beetles Relative to Attractant Structure and Volatility

Submitted to: Journal Of Chemical Ecology
Publication Acceptance Date: June 3, 2004
Publication Date: September 1, 2004
Citation: Hammack, L., Petroski, R.J. 2004. Field Capture Of Northern And Western Corn Rootworm Beetles Relative To Attractant Structure And Volatility. Journal Of Chemical Ecology V. 30(9): 1809-1824.

Interpretive Summary: Primary corn rootworm management options are crop rotation and pesticides often applied to soil at planting without knowledge of pest populations. Rootworms are increasingly able to survive short rotations when adults lay eggs in soybeans before a corn crop or when eggs are laid in corn but lie dormant for two winters before hatching. The pesticides do not reliably suppress pest populations and account for nearly 20% of the insecticide used on U.S. field crops. Corn genetically modified to express bacterial proteins toxic to rootworms will soon provide an effective substitute but not one that is universally satisfactory or safe from resistance development if used even regionally to the exclusion of other control tactics. Chemicals volatilized by host plants guide corn rootworms to appropriate food sources and show promise as additional, environmentally safe tools for rootworm management. Behavioral assays in commercial maize fields and determination of lure volatility under conditions typical of the field were used to assess relationships between lure structure and potency. The study identified a number of new and sometimes potent lures attracting northern and/or western corn rootworm beetles, notably methyl benzoate, methyl 4-methoxybenzoate, and related nitrogenous compounds including methyl anthranilate and several oximes. The nitrogenous compounds were released from lure dispensers at lower than expected rates, making them more potent than assumed in earlier studies. This information helps determine how best to exploit host-plant attractants for management of the corn rootworm pest complex.

Technical Abstract: Attraction of feral northern and western corn rootworm beetles (Diabrotica barberi and D. virgifera virgifera) to a series of mostly nitrogenous and benzenoid synthetic compounds allied with host plant and floral aromas was examined in commercial maize fields. Vaporization rates were obtained for most field-tested compounds and selected additional lures under both ideal and field-representative, but constant, conditions. Although many of the more than a dozen test compounds showed at least trace activity for one or the other if not both species, methyl benzoate and several of its derivatives, notably methyl anthranilate and methyl 4-methoxybenzoate, stood out as effective new lures for females. A variety of structural alterations to methyl benzoate had consistently negative effects on northern corn rootworm captures despite variable effects on release rate, whereas western corn rootworm reacted more strongly to methyl anthranilate and methyl 4-methoxybenzoate than to the considerably more volatile parent compound. Phenylacetaldoxime was attractive to females of both species, but no more so than syn-benzaldoxime, included as reference. A disproportionately low release rate occurred for benzaldoxime, as well as other nitrogenous lures, under field compared with ideal conditions. The attractiveness of salicylaldoxime to northern corn rootworm, despite its low field release rate, combined with the unattractiveness of methyl salicylate having a methyl ester in place of the oxime group, similarly highlighted importance of the oxime moiety for reactivity of this species.