Determining Factors and Economic Injury Levels for Sphenophorus levis for Chemical and Biological Control in Irrigated and Non-irrigated Sugarcane Crops.

Globally, people use sugarcane (Saccharum officinarum) to produce sugar and ethanol. Rainfed or irrigated sugarcane agricultural systems are available. Among the pests affecting this crop, the weevil Sphenophorus levis, Vaurie 1978 (Coleoptera: Curculionidae), is increasingly becoming a significant threat in southern South America. Sphenophorus levis populations are controlled using chemical or biological measures. Control decisions hinge upon the economic injury level (EIL). The EIL delineates the pest density that results in financial losses for producers. This study aims to determine the EIL for S. levis, considering the factors favoring this insect pest and chemical and biological control methods in rainfed and irrigated systems. The intensity of S. levis attacks was monitored in commercial sugarcane plantations over four years in João Pinheiro, Minas Gerais, Brazil. Sampling occurred in a 50 × 50 × 30-cm-deep trench dug in the soil surrounding the sugarcane clump. The total number of stumps in the clump, including those attacked by S. levis, was tallied. The EILs for this pest were 5.93% and 4.85% of targeted stumps for chemical control in rainfed and irrigated crops, respectively. Biological control in sugarcane plots resulted in an EIL of 4.15% and 3.40% for stumps attacked in rainfed and irrigated crops, respectively. Pest attacks were more severe during rainy years and in older sugarcane crops. The EIL values determined in this study could inform integrated pest management programs for sugarcane crops.

Response of Doru luteipes (Dermaptera: Forficulidae) to insecticides used in maize crop as a function of its life stage and exposure route.

The present study aimed to evaluate insecticide toxicity to Doru luteipes (Scudder), a major predator of maize pests. Lethal and sublethal effects were assessed on nymphs and adults exposed to the insecticides through contact (maize leaves) and ingestion (prey eggs) routes. Tested insecticides included a biopesticide (Spodoptera frugiperda multiple nucleopolyhedrovirus, SfMNPV), modern (flubendiamide and metaflumizone), and older neurotoxins (imidacloprid + ß-cyfluthrin). The imidacloprid/ß-cyfluthrin mix was highly toxic (100% mortality) to the predator, regardless of the exposure route and predator stage. Metaflumizone caused mortality higher than 95% and 45% of nymphs and adults. Flubendiamide and SfMNPV were the least toxic insecticides, not differing from the untreated control in any of the assessed endpoints. Adult tibial length did not differ among treatments. Metaflumizone impaired egg consumption by nymphs and walking distance of adult D. luteipes. Overall, the insecticides caused a more pronounced effect on D. luteipes nymphs than on adults and were more toxic by the contact route. From these findings, flubendiamide and SfMNPV are safer for D. luteipes and should head insecticide choice in integrated pest management programs in maize.