Spring Wheat Production and Associated Pests in Conventional and Diversified Cropping Systems in North Central Montana

Producers in the northern plains are diversifying and intensifying traditional wheat (Triticum aestivum L.)-based cropping systems by reducing summer fallow and including legume and oilseed crops. This study examined the influence of diversification and intensification on spring wheat yield and quality and associated insects, diseases, and weeds. Research was conducted during the 1998 through 2000 period in farm fields in north central Montana. Conventional rotations included either hard red spring wheat–spring barley (Hordeum vulgare L.)–fallow or spring wheat–fallow. Diversified rotations included replacement of fallow with either annual pulse crops or cool-season oilseeds. Preplant soil water was less in diversified rotations, but residual nitrate was not influenced by rotation type. Insect pests and beneficial arthropods were in greater numbers in conventional rotations. Incidence and severity of crown and root rots of wheat were similar between rotation types, but foliar leaf spot diseases were greater for wheat in conventional rotations. Weed densities were not influenced by rotation type. Spring wheat yield, tiller density, and test weight were greater in conventional rotations. Spring wheat in diversified rotations had greater drought stress. Diversification and intensification of spring wheat systems may reduce pests and decrease wheat productivity, particularly when precipitation is inadequate.