Iscas tóxicas no controle de Linepithema micans (Forel, 1908) (Hymenoptera: Formicidae) e Eurhizococcus brasiliensis (Wille, 1922) (Hemiptera: Margarodidae) na cultura da videira

Abstract

In Brazil, Eurhizococcus brasiliensis (Wille) (Hemiptera: Margarodidae) is considered to be the main pest of vine plants, attacking the roots of cultivated and wild plants. Linepithema micans (Forel, 1908) (Hymenoptera: Formicidae) is the primary agent responsible for spreading the Eurhizococcus brasiliensis, which are attracted by the honeydew excreted by the scale insect. In this work, the effect of a hydramethylnonbased granular toxic bait on the control of L. micans and E. brasiliensis in grapevines was evaluated on young grapevines. An experiment was conducted in a greenhouse in October 2014 and planted in individual pots were used to select different formulations of toxic baits based on hydramethylnon (small granule, large granule, cereal and gel) for the control of L. micans. The toxic baits were provided ad libitum in bait holders, with baits being replaced weekly. Weekly evaluations were carried out during a period of 10 weeks, with the number of foraging ants being counted every 10 minutes during 1 hour, in an aqueous solution of 70% inverted sugar. The best formulation of toxic bait selected in greenhouse was evaluated in the field in two experiments, carried out in areas naturally infested withe the scale and L. micans. In the first experiment 450 g/ha/week of the toxic bait were applied in Flores da Cunha, RS, and in the second, one and three weekly applications of the same dose were evaluated in Caxias do Sul, RS. In August 2014, seedlings from the Paulsen 1103 rootstock were planted in Flores da Cunha and in November 2015 in Caxias do Sul. The ants was monitored weekly in-ground pitfall traps using a honey and water solution (70%) and sardine conserved in oil absorbed in cotton wool as food attractants.The evaluation of the experiments was carried out in May of 2015 (Flores da Cunha) and 2016 (Caxias do Sul), counting the number of scale insects present in the roots.The experiment conducted in a greenhouse, the hydramethylnon based toxic bait in the formulation small granule and large granule controlled the ant population in the first 4 weeks of application.The gel formulation of the hydramethylnon toxic bait also provided 100% mortality of the population of ants; however, its control was slower when compared with the other two formulations and the cereal formulation did not differ from the control. The small granule toxic bait, applied weekly, effectively reduced the infestation of L. micans, controlling 100% of the population of ants and reducing the infestation of E. brasiliensis by 99.9%. When the number of bait applications was reduced to 1 to 3, there was a 100% reduction in the ants in the treatment that received three applications until the fourth week after application of the bait, but the colonies were re-establishment.The small granule toxic bait, applied weekly, effectively reduced the infestation of L. micans in greenhouse and field.The reduction of the number of applications (one and three times) did not provide satisfactory control and it will be 10 necessary to adjust the number of treatments for an efficient and economical control of the two species.