Spatial distribution of lysiphlebus testaceipes (Cresson) (Hymenoptera: Aphidiidae) in cotton grown in a narrow system

Abstract

In the present study, the effects of the densification of cotton on the spatial distribution of the aphid parasitoid Lysiphlebus testaceipes (Cresson) (Hymenoptera: Aphidiidae). The three spacings adopted were: 0.40 m x 0.20 m (E1), 0.80 m x 0.20 m (E2) and 1.60 m x 0.20 m (E3). A randomized block design with four replications was used. The results showed that the spatial arrangement of cotton modifies the dispersion pattern of L. testaceipes. The parameter b of the Taylor equation was higher than the unit in the spacing: 0.40 m and 1.60 m, while in 0.80 m the value of b was lower than the unit. Therefore, populations of L. testaceipes in conditions of spacing between lines of 0.40 m and 1.60 m are distributed in an aggregate form, however they are uniformly distributed in 0.80 m. The Iwao model revealed that for the spacing: 0.80 m and 1.60 m there is a trend of repulsion of individuals, since the values of the constant a were less than 1. The Nachman model was adjusted only for the population data in cotton grown at 0.80 m, therefore, for this system, plans that aim to estimate the population level of L. testaceipes can be based only on presence / absence observations, instead of individual counting. The present study results are relevant to strategies for the release and conservation of L. testaceipes for biological control of aphid populations in cotton.