Pest management through tropical tree conservation

Tropical trees can provide various ecological services to adjacent agricultural environments, including maintaining and amplifying the numbers of beneficial insects. In Mexico, certain tree species harbor a diverse guild of hymenopteran parasitoids that attack pest fruit flies (Diptera: Tephritidae) and are at the same time sources of valuable hardwood timber. Indigenous trees and their associated fauna are slowly disappearing due to forest clearance and the expansion of crop monocultures. Here we explore the relationship among pest and non-pest fruit flies, their fruit-hosts and parasitoids in the context of mango orchards and surrounding patches of uncultivated vegetation and propose a novel mechanism to use these associations in favor of conservation purposes and pest management. Trees of conservation biological control interest are classified as: (1) parasitoid multiplier plants, species that serve as alternate hosts for key fruit fly pests when their commercial hosts are not available, but in which they are unusually vulnerable to parasitism; (2) parasitoid reservoir plants, native or introduced trees in whose fruits non-pest fruit flies serve as hosts to generalist parasitoids that are able to attack pest tephritids in other species of commercially grown fruit; and (3) pest-based parasitoid reservoir plants, native or introduced species that are not economically important locally, but which harbor fruit flies that would be pests in other circumstances and that serve as hosts for parasitoids of the important pests in the vicinity. Protection, multiplication and dissemination of such tree species has the potential to increase the number of naturally produced fruit fly parasitoids and could assist in the management of tephritid pests in areas where destruction of forests has impoverished the historical sources of fruit fly natural enemies. Tropical forest conservation may help resource-poor farmers reduce crop losses, increase biodiversity within fruit-growing regions and conserve native forests for both conservation purposes and commercial use of native hardwoods.