Bioecologia e nível de dano econômico de Liogenys fusca Blanchard, 1850 (Coleoptera: Melolonthidae) no Rio Grande do Sul

Abstract

The white grub Liogenys fusca is an important pest of soil Midwest Region of Brazil, his injuries have been recorded in crops such as corn, soybeans and oats. The objective of this study was to study the bioecological aspects of Liogenys fusca on Rio Grande do Sul and to determinate the economic injury level (EIL) of the insect on the soybeans. Chapter I emphasis on the characterization of the development phases of Liogenys fusca and the dynamic of this population on Rio Grande do Sul. The study was performed in Manoel Viana, RS, throughout soil sampling held on a monthly basis during 2010 and 2011 years. The insect period of occurrence throughout the year and the location of these in the soil were evaluated. Chapter II emphasizes the economic injury level (EIL) of L. fusca on soybeans. A field experiment was conducted in Santa Maria, RS, on the harvest year of 2010/2011, testing four different populational levels of second and third instars larvae of L. fusca (4, 8 and 12 larvae/m2). The evaluated parameters were: initial plant population, final plant population, plant height at 15, 30 and 60 DAE (days after emergence) and yield (kg/ha). The EIL was estimated through the equation adapted from Pedigo (1999). Liogenys fusca is an univoltine specie. Larvae were sampled between the months February to November. The pupae were found in the interior of galleys built in the soil at a profundity of until 20cm from September through November. The adults were sampled from December through February. The economic injury level (EIL) of L. fusca on soybeans was ranged from 0,12 to 0,44 larvae/m2 as varied cost control. Each increased larvae per m2 effected a yield loss of 151,30 kg/ha on the soybeans.