Managing for Fine-Scale Differences in Inoculum Load: Seeding Patterns to Minimize Wheat Yield Loss to Take-all

摘要

For pathogens with highly localized inoculum, controlled positioning of susceptible plants can be used to delay exposure to the pathogen. For example, when wheat is direct-drilled in fields where wheat was infected by Gaeumannomyces graminis var. tritici (Ggt) in the previous season, the remaining rows of wheat crowns serve as an inoculum source for the new wheat planting. In order to determine how different seeding patterns of wheat might affect yield loss to Ggt, we constructed a mathematical modelin three stages. First, we calculated the probability density function for the distance between a new seed and the nearest old row of crowns for two main planting scenarios: parallel to the previous year's rows or at an angle to them. Second, we used estimates from Kabbage and Bockus [Kabbage, M. and Bockus, W. W. 2002. Plant Disease 86, 298-303] of the yield loss to Ggt as a function of the distance between wheat seed and inoculum source. Third, we combined these two models to estimate the average yield loss for different planting patterns. We estimated that planting parallel to and between the previous year's rows would cut yield loss almost in half for a typical row spacing compared to angled planting, provided there was not an important offset, orbias, in the position of the parallel planting. Planter wobble was relatively unimportant if there was no systematic bias in position.