Pollen Toxicity from Seed-Treated Cotton on Bees and Pollen Collection Capacity

Ellen P De Souza,Rosalia Azambuja,Valter V Alves Junior,Paulo E Degrande,Ricardo O Dos Santos,Rafael A Da Silva,Mateus F Leal

doi:10.5539/jas.v9n11p154

Abstract

Apis mellifera bees that forage in agricultural fields may be exposed to pesticides through many routes. One of them is the collection of pollen contaminated with insecticides. In this study, we evaluate the mortality of adult honeybees exposed to pollen from cotton plants whose seeds were treated with insecticides thiamethoxam, clothianidin, imidacloprid and fipronil, and the pollen collection capacity of adult honeybees in cotton fields. Bee mortality based on linear regression analysis showed significant differences, but no differences were noted among treatments. According to the contrast analysis of the mean groups of insecticides against the mean of the control group, no significant differences were found, indicating a natural mortality for all treatments including the control. Quantitative analysis of the pollen revealed the presence of only cotton pollen grains on bees, indicating floral fidelity of Africanized honeybees. Pearson’s correlation coefficient was positive, but statistically insignificant, for increase in pollen collection with time.

Highlights

Cash crops, such as cotton, are susceptible to the pest attacks during growth, owing to the large areas they cover, among other factors
Concerns regarding the treatment of seeds with systemic insecticides for pest control during the early stages of development have been raised, owing to possible dispersion of high concentrations of neonicotinoids, such as thiamethoxam, clothianidin, imidacloprid, and the pyrazole fipronil in the environment, which could kill pollinators while foraging in agricultural fields (Krupe et al, 2012)
The mortality rates observed during the experiment where A. mellifera adults were exposed to pollen of plants grown from seeds treated with clothianidin, imidacloprid, thiamethoxam, and fipronil were similar to the natural rates

Summary

Introduction

Cash crops, such as cotton, are susceptible to the pest attacks during growth, owing to the large areas they cover, among other factors. Concerns regarding the treatment of seeds with systemic insecticides for pest control during the early stages of development have been raised, owing to possible dispersion of high concentrations of neonicotinoids, such as thiamethoxam, clothianidin, imidacloprid, and the pyrazole fipronil in the environment, which could kill pollinators while foraging in agricultural fields (Krupe et al, 2012). Some studies have found residues of these pesticides in pollen, nectar, bees, and in the soil after planting, in addition to herbicides, fungicides, and acaricides (Mullin et al, 2010; Gill et al, 2012). Others have pointed out a synergistic effect of these residues combined with viruses and mites; prolonged exposure to these compounds can weaken the bees, favoring the development of pathogens (Mullin et al, 2010; Gill et al, 2012)

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