Population dynamics and distribution of Sitophilus zeamais in peach and apple orchards

O objetivo deste trabalho foi avaliar a flutuação populacional de Sitophilus zeamais (Coleoptera: Curculionidae) e determinar a distribuição deste inseto‑praga nas plantas de pessegueiro e macieira na região de Pelotas, no Rio Grande do Sul. A flutuação populacional foi avaliada nas safras 2009/2010 e 2010/2011, por meio de monitoramento semanal com armadilhas dos pomares, durante aproximadamente cinco meses. Foram usadas dez armadilhas do tipo Pet‑milho por hectare, posicionadas a 1,7 m do solo, distribuídas de maneira equidistante nas bordas e no centro do pomar. A distribuição do inseto nas plantas foi avaliada nos frutos dos terços superior, mediano e inferior das plantas, na cultivar de maçã Eva e nas cultivares de pêssego Sensação (ciclo precoce), Eldorado (ciclo tardio) e Eragil (ciclo tardio). Em macieira, o ataque de S. zeamais ocorreu por cinco a sete semanas, e, em pessegueiro, por três a quatro semanas. Foi observado maior número de S. zeamais machos no início da infestação dos pomares, principalmente nos frutos do terço superior das plantas. Nas semanas seguintes, a maior infestação de frutos se deu no terço médio. O ataque de Sitophilus zeamais ocorre tanto em cultivares precoces como em tardias de pessegueiro, com pico de ataque no período de colheita.The objective of this work was to evaluate the population dynamics of Sitophilus zeamais (Coleoptera: Curculionidae) and to determine the distribution of this pest in plants of peach and apple orchards, in the region of Pelotas, state of Rio Grande do Sul, Brazil. Population dynamics was evaluated in the 2009/2010 and 2010/2011 growing seasons by weekly monitoring the orchards with traps for approximately five months. Ten “Pet‑milho”‑type traps were used per hectare, positioned 1.7 m above the ground, distributed equidistantly in the borders and in the center of the orchards. Insect distribution in plants was evaluated in fruits from the top, middle, and bottom portions of the plants, in the apple cultivar Eva and in the peach cultivars Sensação (early cycle), Eldorado (late cycle), and Eragil (late cycle). In apple, S. zeamais attack occurred for five to seven weeks, and in peach, for three to four weeks. A greater number of S. zeamais males was observed at the beginning of the orchard infestation, mainly in fruits from the top portion of the plants. In the following weeks, the highest infestation of fruits occurred in the middle portion. Sitophilus zeamais attack occurs both in early and late cultivars of peach, with a peak attack at the harvesting stage

RESIDUAL EFFECTS OF PESTICIDES IN PEACH ORCHARDS ON THE MAIZE WEEVIL Sitophilus zeamais (COLEOPTERA: CURCULIONIDAE)

ABSTRACT The aim of this study was to evaluate the residual effect of pesticides sprayed on peach orchards on S. zeamais. The study consisted of two experiments, according to the method of pesticide application. For Experiment I, pesticides were directly sprayed on peach trees and in Experiment II, the application of pesticides was performed under laboratory conditions. In both Experiments, the effect of pesticides was assessed in laboratory through the release of ten weevils per peach fruit. The effect of treatments was assessed by variable number of surviving insects. The results for pesticides [a.i. (ml or g.100L)] have shown that application of treatments in the field (Experiment I), malathion (200) presented persistence at 1DAT (Days after treatments spraying) and control higher than 80%, and thiametoxan (30) up to 3 DAT , while for phosmet (200) and fenthion (100), the control percentage was over 70% at 1 DAT . Under laboratory conditions, the application of the same insecticides showed control of 100% at 120 HAT (Hours after treatment application). In this context, the use of insecticides by spraying plants must be considered an alternative method for the control of S. zeamais in peach, being necessary to the development and adoption of new control tools for its management