Atividade de inseticidas em tratamento de sementes sobre o manejo da cigarrinha Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) e do pulgão Rhopalosiphum maidis (Fitch, 1856) (Hemiptera: Aphididae) em milho

Abstract

The maize crop (Zea mays L.) is of extreme importance in Brazil, and one of the things that has been affecting its productivity a lot is the severe attack of early pests, like the corn leafhopper Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) and the corn aphid Rhopalosiphum maidis (Fitch, 1856) (Hemiptera: Aphididae), vectors of the corn stunts, maize rayado fino virus and maize common mosaic virus. The objective of this study was to evaluate the interaction between insecticide treated corn seeds and the use of silicon fertilization, to control D. maidis and R. maidis in field conditions. The treatments consisted of presence and absence of silicon fertilization, and the corn seeds treated with 4 different products. The plots with silicon were applied with 600kg/ha of calcium silicate and the plots without silicon were applied with limestone at the dosage of 800 kg/ha. The soil was incubated for 51 days before sowing the corn. The seeds were treated manually on the same day they were planted with the products Cruiser® (Tiamethoxam) 800mL c.p./100kg seeds, Gaucho® (Imidacloprid) 800mL c.p./100kg seeds, Poncho® (Clotianidin) 400mL c.p./100kg seeds and CropStar® (Thiodicarb + Imidacloprid) 350mL c.p./100kg seeds. The evaluations to quantify the corn leafhoppers and aphids started seven days after emergence (DAE) and were conducted until 42 DAE with a seven days interval. For that evaluation 10 plants per plot were randomly selected and the number of leafhoppers and aphids counted. At 28 and 42 DAE besides the quantification of leafhoppers and aphids in the field, two other evaluations were conducted, where 10 plants per plot were randomly removed and taken to the laboratory for measurement of plant height to the Top Visible Dewlap (TVD) and quantification of the pests in the corn cartridge. The insecticides used in the seed treatment Cruiser®, Gaucho® and CropStar® had 67, 70,5 and 82% efficiency in the control of the corn leafhoppers respectively, no significant control was observed for the aphids, however no effect of the resistance induced by silicate fertilization was observed.