Suitability of Hybrid and Landrace Maize Plants Within Conventional and Organic-Polyculture Maize Agroecosystems for Hosting Parasitic Wasps

Abstract

Abstract Polycultures and conventional monoculture have different effects on insect pests and natural enemies. Little is known about the parasitoid response to landrace and hybrid plants damaged by insect pests within organic-polyculture agroecosystems vs. monoculture ones. The aim of the present study was to compare the suitability of these agroecosystems for hosting parasitic wasps by evaluating the parasitism rate, parasitoid abundance, and species composition on landrace and hybrid maize races within organic-polyculture and conventional maize agroecosystems. This study was performed within the Mesoamerican region where maize was originally domesticated and where the maize insect pest Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae) originated. Maize plants of landrace and hybrid varieties were used to attract egg parasitoids of D. maidis within each of the two agroecosystems; conventional maize monoculture and an organic-polyculture of landrace maize, beans, and squash, which also included weed plants. Four treatments were conducted in this field experiment: 1) landrace-within organic agroecosystem, 2) hybrid-within organic agroecosystem, 3) landrace-within conventional agroecosystem, and 4) hybrid-within conventional agroecosystem. A community of parasitic wasps, of which the micro-wasp Paracentrobia sp. (Hymenoptera: Trichogrammatidae) was the most abundant member, was found attacking the D. maidis eggs in both agroecosystems. The parasitism rate and parasitoid abundance were similar among the four treatments. However, the abundance of parasitoids was greater in the conventional maize monoculture. Bait plants (landrace and hybrid maize) within each agroecosystem did not show differences in either parasitoid abundance or parasitism rate.