Effects of management intensification on coccids and parasitic hymenopterans in coffee agroecosystems in Mexico.

Biodiversity maintained in agroecosystems contribute both to conservation and economic goals via various ecosystem services. However, management intensification can negatively affect biodiversity in agroecosystems. Effects of management intensification on biodiversity and its function in agroecosystems need to be explored to develop agricultural practices where conservation and economic goals are successfully integrated. I conducted studies in 4 coffee agroecosystems under low to high management intensities in Chiapas, Mexico to investigate (1) the diversity and abundance of hymenopteran parasitoids, and (2) the function of a natural enemy complex in controlling a potential pest species, the coffee green scale, Coccus viridis. Parasitoid collections produced a total of 17,366 individuals and 308 morphospecies representing 29 families. Total estimated species richness exceeded 200 in all sites, however, negative effects of management intensification was indicated by >10% reduction in species richness. The abundance of parasitoids also declined along the intensification gradient. Similarities in species compositions were affected more by the proximity of sites than similarities in management intensity. In addition, the shade layer had greater species richness regardless of management intensity and species compositions of the canopy and coffee layers showed >50% overlap. Surveys showed low abundance of C. viridis regardless of management intensity; however, C. viridis infestation caused 40% reduction in coffee fruits weight. Experiments showed that 90% of C. viridis mortality was caused by the coccinelid beetle, Azya orbigera; however, in a more intensively managed site where insect natural enemies were less abundant, 61% of C. viridis mortality was caused by the entomophagous fungus, Verticillium lecanii , and 39% by predation. Surveys showed that parasitism of C. viridis could be >10%; however, experimental results indicated that the presence of coccinelids reduces it to C. viridis appeared to change under different conditions. Thus maintaining a diverse set of natural enemies can be important in achieving an effective pest control in coffee agroecosystems.PhDBiological SciencesEcologyParasitologyPlant sciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126581/2/3253423.pd