APS Abstracts of Presentations

Mechanisms of peanut early leaf spot reductions in maize intercrops. M. A. BOUDREAU (1), B. B. Shew, and L. E. Duffie (2). (1) Warren Wilson College, Dept. of Biology, Asheville, NC; (2) North Carolina State University, Dept. of Plant Pathology, Raleigh, NC 27695. Phytopathology 93:S10. Publication no. P-2003-0067-AMA.

Early leaf spot reductions in peanut-maize intercrops may be due to effects on dispersal or infection phases in the life cycle of the causal agent, Cercospora arachidicola. Infection- related mechanisms were evaluated in 11 × 11 m plots near Asheville, NC in 3 experiments in 2000 and 2 in 2001, arranged in a randomized complete block design with 3 blocks and 5 treatments: peanut monocrop, strip intercrop (4:4 peanut and maize rows, respectively), and patterns of 1:1, 2:1, and 3:1. In each experiment, 5 randomly-placed peanut plants were inoculated with C. arachidicola conidia in each plot and evaluated for disease severity after approximately 21 days. Severity was not affected by intercropping in the third inoculation of 2000 nor in the 2001 trials. Where an effect was seen in 2000 (P < 0.01), severity was highest in strip intercrops and lowest in the 1:1 intercrop, with monocrops intermediate. The results suggest that alterations in the infection phase of the pathogen's life cycle do not have a major role in overall disease reductions seen in other work.