Efeito do uso de defensivos agrícolas sobre a diversidade de polinizadores e produtividade do girassol (Helianthus annuus L.)

Abstract

Pollination service is considered one of the major ecosystem services on the planet and is mostly performed by insects and mainly by bees. Pollination is essential for sexual reproduction of Angiosperms and contributes to maintaining plant species diversity and agricultural production. However, in the last years, studies have shown a decline in bee populations caused bythe indiscriminate use of agrochemicals among other factos. Brazil stands out as one of the leading agricultural producers in the world and,at the same time, as a great pesticides consumer. It is estimated that the annual consumption of these products try exceeds 300.000 tons. Despite these negative effects the use of agricultural pesticides is still needed in order to ensure agricultural production, especially in monocultures. Among them, we highlight sunflower culture, which presented increasing development in the last years in Brazil as require the intensive use of pesticides, and are dependst on pollinators for seedproduction. Considering the high dependence on pollinators and the high useof pesticides insunflower this study aimed to verify whether the use of pesticides in sunflower cultivation affects bee diversity (non-Apis and Apis) and consequently, pollination and production. The study was conducted at Fazenda Água Limpa, which belongs to Universidade Federal de Uberlândia, during May to August of 2015. We established two sunflower crops with 10 m space for the following treatments: pesticides use (SD) and agricultural defensive bis (tiocarbamato) (CD), with insecticide purpose. During 8 consecutive days,we made t observations of floral visitors in both treatments in ten sunflower inflorescence per treatment. After maturation of the sunflower inflorescence maturation, we weighed the achenes and performed oil extraction from the seeds.There was no significant difference in pollinators’ richness of between treatments. However the abundance of visits was greater in SD treatment for both pollinators’ groups Apis and Non-Apis. There was a higher production of both seed mass and quantity of oil in the pesticides free treatment, suggesting negative effect on pollinator visits. This effect was found mainly on social bees, and may be related to defensive neurotoxic effect , which jeopardize bee geolocation,as well as the communication between them regarding food source location. The use of crop protection produced a depressing effect on the bee abundance of sunflower crop, which directly affects its production. The use of pesticides is only one form of pest control and should be used rationally, thus minimizing most of its effect on pollinators and ensuring a satisfactory production.