|Van Driesche, Roy|
Submitted to: Conservation Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2014
Publication Date: N/A
Citation: Interpretive Summary: Fruit flies attack hundreds of fruits and vegetables and are the cause of trade barriers wherever they occur. One means of suppressing their numbers and lowering the risk of invasion into the USA is to increase the numbers of their natural enemies. Scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida in collaboration with colleagues at the Instituto de Ecologia, Xalapa, Veracruz, Mexico have designed a proposal to replant native fruit trees in Mexican agricultural settings. These trees support fruit fly parasitoids and fruit flies, but not pest species of fruit flies. In addition, several tree species produce valuable timber and this serves as an added incentive for growers to participate in a conservation biological control program. At this point, native “banker-plant” tree seedlings are being given free to selected village farmers.
Technical Abstract: When discussing the need to improve conservation programs for native forests, arguments such as the role of vegetation in water catchment and soil conservation or as sources of food, medicines, firewood and lumber, and habitat for wildlife are commonly used. Here we argue that many native species of tropical trees, in addition to being valuable sources of fine woods, also provide an important service as reservoirs of parasitoids that play an important role in controlling pest insects. We use as our example an important group of agricultural pests (tephritid fruit flies [Diptera: Tephritidae]), their native parasitoids, and importantly, the trees on which both groups of these insects live. In undisturbed and disturbed stands of native vegetation, and in small scale agroecosystems and backyard gardens in Veracruz and Chiapas, Mexico, we have discovered several tree species that are host plants of pest fruit flies but that also generate up to 3000 fruit fly parasitoids / fruiting season (= “killing-ground” or “parasitoid-multiplier species”). In some cases, these trees harbor specialist fruit flies of no economic importance that are often now rare and slowly disappearing. The flies in such trees could serve as harmless hosts of parasitoids that would later disperse to attack pest species in agricultural settings (= “banker-plant” or “diversity-enhancing species”). Here, we propose a scheme aimed at protecting, multiplying, and managing tree species that serve as important parasitoid reservoirs in areas where destruction of native tropical forests is rampant. We propose to protect and replant selected species of trees that conserve or augment fruit fly parasitoids in forest areas, along rural roads and trails, in patches of disturbed and undisturbed native vegetation and in backyard gardens and mixed agroecosystems (e.g., fruit orchards, shaded coffee plantations) to increase the number of naturally produced fruit fly parasitoids. Nonchemical pest fruit fly control would be achieved by increasing the number of parasitoids that attack fruit flies outside of orchards, significantly reducing numbers of flies invading orchards and backyard gardens. Tree planting/conservation would also provide local farmers with sources of highly valued lumber since the wood of some of the trees we propose to protect command high market prices. Finally, we envision highly targeted augmentative releases of parasitoids onto wild tree hosts at times when fruit flies numbers are restricted to small numbers of such hosts and hence are especially vulnerable to such controls. We believe our scheme is practical, will help resource-poor farmers reduce crop losses at little cost, will increase the biodiversity of agroecosystems, and will help larger scale efforts aimed at protecting native vegetation for conservation purposes and commercial use.