Land use changes from native vegetation to agriculture, livestock grazing, and urban development are among the main problems related to biodiversity loss worldwide. In this paper we evaluate how land use changes (eucalypt plantation and pasture) affect the richness and assemblage of wasps (Braconidae, Ichneumonidae, Pompilidae, and Vespidae), in comparison with nearby areas with native vegetation in the Cerrado. Specimens were collected at six points, with two Malaise traps at each location. The collections were performed monthly for 10 d, for 12 mo. A total of 773 hymenopterans of the selected groups were collected, representing 253 species or morphospecies. Richness of the families Ichneumonidae and Pompilidae between the areas did not present significant differences. For the families Braconidae and Vespidae, the richness was greater in the eucalypt plantation and pasture areas compared to the native area. Species composition in the native habitat was different from either of the managed habitats in the studied environment. Furthermore, the composition of wasps in native areas varied less throughout the sampling campaigns when compared with the pasture and eucalyptus sites. In native areas, 85 exclusive morphospecies were found. Thus, changes in land use may cause changes in the composition of wasp species, since areas with native vegetation presented more heterogeneous and stable environments than the other land uses. The maintenance of native areas, even if close to planted forest and/or pasture areas, could be the best way to combine forest productivity with biodiversity conservation.

The plant surface is one of the first sites of contact with microorganisms, where structures such as the cuticle and trichomes are responsible for interfering with this initial interaction. Trichomes, while protecting plants from microorganisms, can also facilitate infection by pathogens. The density of trichomes varies among species, and the amount and type of these structures in plant organs can confer resistance or susceptibility of plants to microorganisms. The trichomes, non-glandular and glandular, act as a barrier, preventing the adherence of the infective structures of the pathogens on the plant surface. In addition, glandular trichomes also secrete exudates (products of plant metabolism), which have antimicrobial properties, negatively interfering with the development of many bacterial and fungal diseases. However, both trichomes are favorable sites for the penetration and multiplication of plant pathogens, possibly because they provide a certain level of moisture and nutrients for the development of fungi and bacteria. Contrary to the view that trichomes only provide protection against plant pathogens, by hindering their adhesion, they can also become preferential sites for infection.