Tillage and Chlorpyrifos Treatment Effects on Peanut Arthropods—An Incidence of Severe Burrower Bug Injury
Authors: Chapin J. W. , Thomas J. S. , Joost P. H. 
Published: April 2010

Abstract
A 2-yr study was conducted on the effects of tillage and soil insecticide (chlorpyrifos) treatment on peanut arthropod pests. A 3 by 2 split-plot experiment with five replications was subjected to factorial ANOVA. Main plot treatments consisted of three tillage systems: conventional moldboard plow, strip tillage into a killed wheat cover crop, and strip tillage into corn stubble residue. Subplot insecticide treatments were granular chlorpyrifos applied at early pegging (growth stage R2) and untreated. Populations of corn earworn, Helicoverpa zea (Boddie), and velevetbean caterpillar, Anticarsia gemmatalis Hübner, were lower in strip tillage systems. Chlorpyrifos applications caused corn earworm outbreaks in all tillage systems, but these applications were more disruptive in strip tillage. Chlorpyrifos treatment also increased populations of fall armyworm, Spodoptera frugiperda (J.E. Smith), but had no measurable effect on velvetbean caterpillar populations. Pod damage from lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), and wire-worms, Conoderus spp., was lower in strip tillage systems, and chlorpyrifos suppressed pod damage in all systems. Threecornered alfalfa hopper, Spissistilus festinus (Say), damage to peanut was greater in the wheat residue strip tillage system. Chlorpyrifos treatment reduced threecornered alfalfa hopper damage in all systems. Spider mite injury was not affected by tillage, but chlorpyrifos treatments resulted in mite outbreaks in all tillage systems. Burrower bug, Pangaeus bilineatus Say, injury to peanut kernels was greater in the strip tillage systems in 1999; and burrower bug injury was suppressed in the strip tillage systems by chlorpyrifos treatment. There was a significant interaction effect for burrower bug injury between tillage and insecticide treatment. Incidence of tomato spotted wilt virus also was reduced by strip tillage. Use of an effective fungicide program and a 3-yr crop rotation out of peanut production probably obscured any potential tillage effects on fungal diseases (southern stem rot, Rhizoctonia limb rot, and leaf spot). However, chlorpyrifos treatment increased Rhizoctonia limb rot incidence. Weed populations were generally greater in strip tillage systems, but postemergence herbicides effectively eliminated any potential confounding effect on yield and grade. Yield was not affected by tillage in either year, and chlorpyrifos had no effect on yield in 1998. In 1999, however, chlorpyrifos increased yield in both strip tillage systems. Neither tillage nor insecticide treatment affected grade (percentage total mature kernels) in 1998, but in 1999 grade was highest in conventional tillage and grade was improved by chlorpyrifos treatment in strip tillage systems. Crop value losses of $249 and $388/ha were attributed to burrower bug injury in untreated corn and wheat residue strip tillage systems, respectively. This injury may have been an anomaly of drought conditions but, given the potential economic impact, burrower bug merits further study in conservation tillage peanut production.