ABSTRACT
ABSTRACT Solitary wasps and bees (Hymenoptera) play a key role in ecosystem and agroecosystem functioning. Crops may benefit from biological pest control and pollination carried out by predatory solitary wasps and solitary bees, respectively. Here, we aimed at evaluating the abundance and faunistic compositions of solitary wasps and bees in respect to land-use (pasture, alley cropping, young fallow and old fallow) over an entire year using trap nests in the Brazilian northeastern state of Maranhão. Land-use did not influence the abundance of solitary wasps and bees, however, levels of dominance, abundance and frequency of the species Pachodynerus guadulpensis Saussure, Isodontia sp. 1, Isodontia sp. 2, Trypoxylon nitidum Smith and Megachile cfr. framea Schrottky varied with land-use. The abundance of wasps and bees varied over the period of the year with populations peeking in January (bees), and June and July (wasps). Relative humidity explained most of the variation for the abundance of wasps while temperature explained higher portions of the variance for the abundance of bees. There was an interaction between period of the year and land-use for the abundance of wasps (but not for bees). We concluded that total population abundance of solitary wasps and bees were not affected by the land-use however, levels of dominance, abundance and frequency of some species of these hymenopterans changed according to land-use. Also, relative humidity and temperature were important environmental variables explaining the abundances of wasps and bees.
ABSTRACT
The present work evaluated the influence of forest distance on predatory solitary wasps' abundance and richness and its relation to the natural biological control of the fall armyworm (Spodoptera frugiperda Smith - Lepidoptera: Noctuidae) in maize. The study consisted of two parallel lines of six experimental maize plots located at an increasing distance from a forest edge. Four trap-nests were placed in the vertices of each plot of the first line to evaluate the abundance and species richness of predatory solitary wasps. The larvae of the fall armyworm were sampled weekly by inspecting ten randomly chosen plants per plot. Predatory solitary wasp abundance (but not species richness) decreased whilst the fall armyworm abundance increased with the distance from the forest. Moreover, population densities of predatory solitary wasps and the fall armyworm were negatively correlated. Results suggested that the crop plantations located near forest fragments might benefit from the reduced pest problems as a result of increased natural biological control.