RESUMO
Africanized and wild bees are sensitive to synthetic insecticides, but may not be sensitive to botanical extracts. In this work, we evaluated the toxicity of botanical extracts with homemade preparations used in agroecological crops and their constituents on the bees Apis mellifera and Partamona helleri. Toxicity bioassays of adult bees were done by means of oral exposure and ingestion, using the insecticide imidacloprid as a positive control. Dietary consumption, respiration rate and bee flight were evaluated as sublethal parameters. Although some extracts were toxic to bees, survival was always higher compared to the results obtained with the imidacloprid, which was lethal to 100% of bees. In dietary consumption, P. helleri consumed less (5 mg/bee) in 3 h than A. mellifera (11 mg/bee), and P. helleri consumed less (7 mg/bee) in 24 h than A. mellifera (22 mg/bee). There was no difference in consumption of food containing plant extracts or food containing water only. We did not detect any adverse effects of the botanical extracts on bee respiration rates or flight. The major constituent of N. tabacum is nicotine (8.4-15.1%), in A. americana it is ß-caryophyllene (11.3%), and in A. colubrina, lupeol (12.2%). Imidacloprid and nicotine were more toxic to bees (LC50 ≤ 1.3 and LC50 ≤ 44.3). Botanical extracts were selective to A. mellifera and the native bee P. helleri, and therefore, have the potential for ecofriendly pest control.
Assuntos
Abelhas/fisiologia , Inseticidas/toxicidade , Extratos Vegetais/toxicidade , Animais , Dieta , Dose Letal Mediana , Neonicotinoides , NitrocompostosRESUMO
Insect pests are one of the factors that most impact plant yield. The magnitude of the losses and the spatiotemporal pest distribution in crops is a result of their interactions with the environment. Therefore, the understanding of the causes of production losses and the pest spatial patterns is important for the development of suitable sampling plans and pest management programs. Thus, this study aimed to quantify grain losses caused by insects and to determine the spatial distribution pattern of arthropod pest species in Bt and non-Bt corn. The prevailing insect pests in the corn ears were the earworm and fall armyworm caterpillars (Helicoverpa spp. and Spodoptera frugiperda), the cornsilk fly (Euxesta spp.), the maize weevil (Sitophilus zeamais), and the square-necked grain beetle (Cathartus quadricollis). The non-Bt corn was more attacked by the caterpillars and the weevil, while Bt corn was more affected by the cornsilk fly Euxesta spp. Spatial dependence was significant for the damage caused by the caterpillars, the grain beetle and the maize weevil in both the Bt and non-Bt corn genotypes. The range of the damage caused by the insects was between 9.0-9.7 m for the caterpillars, 6.9-12.20 m for the cornsilk fly, 10.7-80.4 m for the square-necked grain beetle, and 51.9-170.7 m for the maize weevil. The pattern of the spatial distribution of pest damage in both corn genotypes (i.e., Bt and non-Bt corn) was similar with a prevalence of moderate to strong spatial dependence and aggregate damage distribution. The plants near to the sampling points exhibited injury and infestation levels similar to those of the sampled plants.