Stephen O. Guy

Effects of Tillage on the Activity Density and Biological Diversity of Carabid Beetles in Spring and Winter Crops

Abstract The effects of tillage regimen (conventional [CT] and no-tillage [NT]) on the activity density and diversity of carabid beetles (Coleoptera: Carabidae) was studied by pitfall trapping within a rain-fed cropping system in northwestern Idaho, 2000–2002. The cropping rotation consisted of a spring cereal (barley, Hordeum vulgare L., in 2000 and 2001; and wheat, Triticum aestivum L., in 2002), spring dry pea (Pisum sativum L.) 2000–2002, and wheat (T. aestivum), spring in 2000 and 2001, and winter in 2002. A total of 14,480 beetles comprised of 30 species was captured, with five numerically dominant species [Poecilus scitulus L., Poecilus lucublandus Say, Microlestes linearis L., Pterostichus melanarius Ill., and Calosoma cancellatum (Eschscholtz)], accounting for 98% of all captures. All species including the dominants responded idiosyncratically to tillage regimen. Adjusting for trapping biases did not significantly change seasonal activity density of Poecilus spp. or Pt. melanarius to tillage. More beetles were captured in CT than in NT crops because of the dominance of P. scitulus in CT, whereas species richness and biological diversity were generally higher in NT crops. Observed patterns suggest that direct effects of tillage affected some species, whereas indirect effects related to habitat characteristics affected others. CT may provide habitat preferable to xerophilic spring breeders. A relationship was found between beetle species size and tillage regimen in pea and to a lesser extent across all spring crops, with large species (>14 mm) conserved more commonly in NT, small species (<7 mm) in CT, and intermediate species (7–14 mm) conserved equally between tillage systems.

Impact of Tillage Practices on Hessian Fly-Susceptible and Resistant Spring Wheat Cultivars

Abstract Hessian fly, Mayetiola destructor (Say), is a residue-borne pest of spring wheat that can become important in reduced tillage production systems. The relative abundance of Hessian fly was examined on spring wheat cultivars grown under conventional tillage (CT) and no-tillage (NT) practices in northern Idaho from 2000 to 2002. Six cultivars were tested: Hessian fly-susceptible ‘Penawawa’ and ‘Westbred 936’ and -resistant (H3 gene) ‘Wawawai’, ‘Jefferson’, ‘Hank’, and ‘Westbred 926.’ Hessian fly egg densities were not significantly different among treatments, indicating ovipositing females showed no preference for tillage treatment or cultivar. Mean number of Hessian fly puparia per plant was significantly greater in CT plots during the last sampling in 2000; however, in 2001, NT plots had significantly more puparia than CT plots. Tillage had no significant effect on mean Hessian fly per plant in 2002. Significantly more puparia were observed on susceptible compared with resistant cultivars in 2000 and 2002. In 2001, susceptible Penawawa had significantly more puparia than resistant cultivars, whereas puparial densities on susceptible Westbred 936 were higher than on resistant cultivars other than Wawawai. Yield and 100-seed weight were not affected by tillage treatment. Significant variation in yield among cultivars was observed only in 2000, when fly-resistant Hank yielded the highest. Hank had the highest 100-seed weight in 2000 and 2001, whereas Penawawa and Jefferson had the lowest 100-seed weights each year. Reduced tillage had no consistent effect on spring wheat yield or abundance of Hessian fly under the conditions of our trials, which evaluated small plots.

Early-Season Aerial Adult Colonization and Ground Activity of Pea Leaf Weevil (Coleoptera: Curculionidae) in Pea as Influenced by Tillage System

Abstract The pea leaf weevil, Sitona lineatus (L.) (Coleoptera: Curculionidae), is an important pest of pea, Pisum sativum L., in northern Idaho. Previous research revealed greater relative pea leaf weevil abundance and feeding damage in peas grown using conventional-tillage compared with no-tillage practices. However, the effects of tillage practices on early season colonization and activity by the pea leaf weevil on pea are not fully understood. Aerial traps and pitfall traps were used to assess adult colonization and relative density of adult pea leaf weevil into conventional-tillage and no-tillage pea in northern Idaho during 2005 and 2006. Feeding damage to the crop also was evaluated. During both years, aerial traps captured more pea leaf weevil in May, when crop establishment and early growth occurred, than in later months. Significantly more adult pea leaf weevils were captured in aerial traps in conventional-tillage than in no-tillage plots in May of both years. Significantly more pea leaf weevil were captured in pitfall traps in conventional-tillage plots than in no-tillage plots during the period immediately after peak aerial adult colonization in late May and early June. Crop feeding damage was significantly greater in conventional-tillage than in no-tillage plots in late May and early June. The patterns suggest that more adult pea leaf weevil colonize conventional-tillage pea than no-tillage pea. Pea plants in conventional-tillage emerged earlier and were larger than those in no-tillage during the pea leaf weevil colonization period, possibly accounting for the differences in colonization rates. This leads to greater early season pea leaf weevil infestation of conventional-tillage plots at a critical period for pea development that might ultimately influence crop yield.

No-Till and Conventional-Till Effects on Spring Wheat in the Palouse

Erosion is a major problem in the Palouse region of Idaho. While high residue tillage systems can reduce erosion, crop productivity is a concern. An experiment was conducted near Genesee, ID to assess the effects of no-till and conventional-till on spring wheat (L. emend. Thell.) from 2001 to 2004. Tillage treatments had no effect on spring wheat plant stand, plant height, grain yield, grain hardness, biomass, heads per square foot, or harvest index. Weight of 200 seeds was significantly higher by 0.37 g in no-till treatment, and test weight was 1.2 lb/bu higher in no-till, while grain protein was 0.5% less than in conventional-till. These effects were possibly due to more available soil water retained in the NT areas that were not disturbed by cultivation. These results indicate that well managed no-till systems with adequate nitrogen fertilization could help reduce erosion without detrimental effects on spring wheat yield, quality, and biomass.