Coffee leaf rust (CLR) attacked Central American coffee farms during the post-2011 epidemic, driving production loss across the region. In response, smallholders are adapting a number of agroecological and conventional practices to combat CLR. In particular, Honduran coffee farmers are planting more acreage of coffee varieties that exhibit some resistance to the CLR. However, these resistant varieties are thought to be lower quality than susceptible varieties and many farmers maintain acreage of susceptible varieties to meet buyer demand for these varietals. The intercropping of resistant and susceptible varieties in other crops, like rice, suggests that susceptible varieties may gain some protection from pathogens from the presence of interspersed resistance varieties. However, it remains to be seen if intercropping resistant coffee varieties will benefit susceptible coffee varieties. In this study, we compared CLR, coffee leaf miner, and yield in monocultures and intercrops of susceptible and resistant varieties. To determine the impact of varietal intercropping, we planted 20 organically managed coffee plots of the following treatments: monocultures of resistant varieties, monocultures of susceptible varieties, and intercrops of 20%, 50%, and 80% susceptible to resistant variety ratios. On a monthly basis, we surveyed coffee size (number of branches), the number of leaves with CLR lesions, and the number of leaves with coffee leaf miner damage. We also measured the mortality of coffee plants and the yield after the first year.
Results/Conclusions
We found that resistant varieties had lower mortality rates and fewer CLR lesions, but more leaf miner damage compared to susceptible varieties. Further, resistant varieties had a greater number of branches with harvestable berries than did susceptible varieties during the first harvest. For susceptible varieties, intercropping plots with 50% resistant varieties resulted in lower numbers of leaves with CLR lesions on susceptible plants compared to the susceptible varieties in monoculture. Yield per plot increased with the proportion of resistant varieties planted. These results suggest that resistant varieties outperform susceptible varieties in terms of CLR damage and yield, however they also suggest resistant varieties have more damage from the coffee leaf miner. We only find weak support for the hypothesis that intercropping resistant varieties benefits susceptible varieties, although these results reflect only the first year of planting. As coffee bushes increase in size over time, the impact of intercropping may become more substantial. Nonetheless, this study will provide valuable recommendations for organic coffee farmers in Honduras.