A Study of Abiotic and Biotic Factors Affecting Coffee Rust Infection Rates in a Shade-Grown Organic Coffee Farm

Abstract

Coffee rust disease causes significant losses to coffee bean production, and producers can incur heavy costs managing it with fungicides. Given the potential for coffee rust infection rates to increase with climate change, a better understanding of the factors influencing coffee rust infestation could help coffee producers manage coffee rust cost-effectively. In this study, the effect of the abundance of Lecanicillium lecanii-infected scale insects, shade, variety type, and plant density were compared, with spatial and temporal effects taken into consideration. L. lecanii-infected scales surveyed the year previous to the coffee rust survey decreased coffee rust intensity, while L. lecanii-infected scales surveyed the same year to the coffee rust survey showed a positive relationship under some conditions. Shade decreased coffee rust intensity in 2009 but not in 2010, and varieties had differing probabilities of being infected by coffee rust. Coffee plant density had no effect on rust incidence, but it did seem to affect the dispersal of rust through space. The results suggest that ecological management of L. lecanii-infected scales and variety type may help to decrease coffee rust intensity and incidence.