Boudreau Depicts Intercropping and Leaf Spot of Peanut Challenges
Posted: October 5, 2015
On Monday, October 5, 2015, Dr. Mark A. Boudreau visited the Department of Plant Pathology & Environmental Microbiology to reveal the results of seven years of study on intercropping and leaf spot of peanut. Dr. Bourdeau discoursed with twelve PPEM graduate students who took the opportunity to ask questions over lunch, and he interacted with several faculty members during his stay.
Plant diversity can have a profound impact on disease dynamics, with important applications for enhancing sustainability in modern and traditional agroecosytems. Disease is often reduced by intercropping, but variability can be high. Several management approaches to stabilize this variability for early leaf spot (ELS) and late leaf spot (LLS) of peanut are presented, in experiments conducted with colleagues Barbara Shew and Laura Andrako. The studies took place in North Carolina, over seven seasons and in three phases. In Phase 1, monocrops and alternating row and strip intercrops with maize were artificially inoculated for ELS in an area with little peanut production. Reductions in AUDPC of 37-73% in strip treatments compared to monocrops prompted testing the efficacy of intercropping in intensive production areas for Phases 2 and 3. Additional treatments included cotton strip intercrops, and integration of intercropping with reduced fungicide treatments and partial resistance to leaf spots. In Phase 2, the use of cotton strip intercrops lowered natural ELS epidemics by 25-41% (AUDPC) through delayed disease onset, but maize had inconsistent effects. Intercropping was not effective against LLS, which dominated in Phase 3. Reduced fungicide regimes and partial resistance lowered disease, and in one case interacted with intercropping to enhance disease suppression. Separate studies to determine maize impacts on ELS infection implicated disruption of dispersal as the mechanism of disease reduction. This work demonstrates the importance of the species added and planting pattern in altering disease dynamics, which may interact strongly with the nature of the source inoculum and influence application of intercropping as a management tool.