Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/20/2004
Publication Date: N/A
Technical Abstract: In temperate North America, the Diabrotica pest complex, particularly Diabrotica virgifera virgif-era LeConte and D. barberi Smith and Lawrence, known as rootworms, are the most damaging pest of maize, Zea mays L., with more than 1$ billion (US) lost in terms of control costs and damage. Consequently, this pest complex is the newest target for Bt-mediated, transgenic control by several companies. While all transgenic events are highly effective against neonate Diabrotica larvae, they are less effective against later larval instars. Our research has demonstrated that D. v. virgifera larvae and D. barberi larvae can effectively develop on many alternate grassy hosts commonly found in maize fields, including species such as giant foxtail, Setaria faberi, and large crabgrass, Digitaria sanquinalis. We have also demonstrated in both greenhouse and field studies that Diabrotica larvae can effectively develop on, and cause damage to, Bt-expressing maize when larvae have initially developed on an alternate weedy host. For example, in a greenhouse study where 20 neonate D. v. virgifera larvae were infested in pots containing glyphosate resistant, Cry3Bb1-expressing maize; its glyphosate resistant isoline planted alone and with a grassy weed combination of S. faberi; and D. sanquinalis, where the weeds were treated with glyphosate (killed) 10 days after infestation, results indicate that the presence and subsequent removal of weeds most likely provides D. v. virgifera a larval refuge. Results from the prior example (and additional studies to be presented) have important implications regarding both potential damage and delaying the onset of resistance to these newest tools for management of Diabrotica in maize, not only for North America, but potentially for South American maize growing regions.