Discrimination of infested cotton squares by females of Anthonomus grandis Boheman (Coleoptera: Curculionidae)

A.L. NUSSENBAUM; F. DEVESCOVI; P. SCHIAVO; R. RUSSO; M. FOGAR; M.A. SIMONELLA; I. BONACIC; J.C. SALERNO; J.L. CLADERA ; D.F. SEGURA

Congreso; 1st Joint Meeting ISCE/ALAEQ; 2016

The choice of an oviposition site has a direct impact on the reproductive success of insects, particularly for species that developed in confined patches. Females of Anthonomus grandis, an important pest of cotton in Argentina, seal the oviposition punctures with secretions that are hipothesized to act as a chemical signal that deters other females from ovipositing. In this work, we evaluated the behaviour of females to oviposit in previously infested squares (flower buds of cotton). For this, preference for oviposition in infested vs non-infested squares was studied in choice tests in the laboratory, and the distribution of ovipositions by A. grandis in field collected squares from plants and fallen squares (abscised) were assessed in cotton plots with different infestation levels.In the laboratory, the number of oviposition in infested vs non-infested squares was significantly higher in non-infested squares (t (41) = 2.19; p = 0.03). Furthermore, the rate of acceptance of squares as oviposition substrate was higher for non-infested squares than for infested squares (Chi-square (51) = 6.74; p = 0.03). In the field, a pattern indicating avoidance of infested squares was found in fallen squares sampled in plots with high infestation. In these, a deviation from the Poisson distribution was found, where the trend was to avoid previously infested squares. On the other hand, squares sampled directly from the plant fitted a random distribution in some plots and the avoidance pattern in others. We never found a distribution that deviates towards an aggregated distribution. The same results were found in two consecutive years and in two different provinces.Our results suggest the possible presence of a host marking pheromone affecting female behavior by deterring the oviposition. Knowledge of the behaviour of females and identification of these signals could provide a basis to develop control methods against this important pest.