Diversidade de himenópteros parasitoides em cana-de-açúcar (Saccharum officinarum L.) com diferentes arranjos espaciais de plantas entomófilas

Abstract

Increasing floral diversity with entomophilous plants in crops could be an additional strategy in integrated management programs, providing alternative food resources and shelter for natural enemies in adverse conditions, and reducing the use of chemicals. The objective of this project was to evaluate the influence of spatial distribution of entomophilous plants in association with sugarcane cultivation on parasitoid hymenoptera. The project was conducted at “El Balsamo” farm, Escuintla, Guatemala, and consisted of three treatments: 1) T. erecta and B. pilosa planted between the sugarcane furrow in the form of strips; 2) T. erecta and B. pilosa planted between furrow in dispersed form and 3) monoculture sugarcane (control), with three replications. Six samples per experimental unit were held from April to September (n = 324). Sampling of D. crambidoides injury and parasitism in sentinel eggs were also performed. The data were analyzed using the Generalized Linear Model (GLM). Ecological indices of richness, abundance, diversity, similarity and curves of rarefaction and accumulation of species and individuals were also analyzed. The spatial distribution of T. erecta and B. pilosa (strips and dispersal) increased the presence of parasitoid hymenoptera in the sugarcane crop, helping in the regulation of pests, especially D. crambidoides. The strip treatment showed a greater richness of taxa (64) and accumulation of individuals (1566), followed by dispersed treatment (56 taxa and 1.065 individuals) and control (46 taxa and 656 individuals). This difference was shown by the analysis of non-metric multidimensional scaling (NMDS), resulting in a clear separation between treatments (stress = 0.1338). Cluster analysis also showed that the strips and dispersed treatments are more similar (72%) than the control (57%). In the study, the families Scelionidae (22.12%), Diapriidae (21.33%), Ceraphronidae (17.98%), Encyrtidae (8.70%), Bethylidae (7.27%) and Platygastridae (6.33 %) represented 83.72% of all abundance of insects collected. Strip and dispersed treatments showed no significant difference with respect to the control in the abundance of parasitoid hymenopterans, according to the statistical analysis GLM (p = 0.0066). The injury of D. crambidoides in sugar cane, the results showed that all treatments were different (GLM Quasibinomial analysis, p < 0.05) being lower in the treatment bands. The spatial distribution of T. erecta and B. pilosa (strips and dispersal) increased the presence of parasitoid hymenopterans in the culture of sugarcane, helping in the regulation of D. crambidoides.