Abstract
Brazil is one of the world’s largest producers of maize (Zea mays L.). Cry proteins derived from the bacterium Bacillus thuringiensis (Bt) have been widely used in transgenic maize due to their toxicity and specificity against insects that damage crops. In addition, these plants have been stacked with different herbicide tolerance genes. Non-target insects end up being exposed to Bt proteins and herbicide applications. There is little information on the effects of Bt transgenics and their cultural practices on the behavior of pollinators in genetically modified crops. The aim of this research was to verify the impact of genotypes of genetically modified maize, Herculex®, PowerCore®, and the conventional isohybrid, pulverized or not with herbicides (atrazine, glufosinate-ammonium and nicosulfuron) in bee populations. In order to evaluate the presence of insects, a zig-zag tour was carried out throughout the experimental field, ascertained from visual analysis and direct counting of six plants per plot (the dimensions of the plots were 2.5 x 10 m with five maize lines spaced 0.50 m between rows and 0.36 m between plants) randomly, 18 days after spraying herbicides in the area. Apis mellifera (L.) (Hymenoptera: Apidae), Tetragonisca angustula (L.) (Hymenoptera: Apidae) and Trigona spinipes (F.) (Hymenoptera: Apidae) were the pollinator species identified in the crop. It was observed that the incidence of pollinator insects varied according to cultivars and herbicides tested; however, the PowerCore® genotype experienced more visitation of pollinating bees independently of the herbicide treatments.
Highlights
Brazil is one of the world’s largest producers of maize (Zea mays L.) with a total production of 60 million tons and average yield in the first harvest of 5.4 t ha-1 (Conab, 2016)
As the A factor represented by the genotypes Herculex® - transgenic maize [Bacillus thuringiensis (Bt) Cry1F protein], PowerCore® - stacked transgenic maize [Bt Cry1F, Cry1A.105, Cry2Ab2 proteins and CP4 EPSPS protein and the conventional isohybrid - maize sensitive to the S. frugiperda and herbicide
Maize is tolerant to the atrazine herbicide, which is recommended for the control of dicot plants in grass crops and its site of action is the protein D1 in photosystem II
Summary
Brazil is one of the world’s largest producers of maize (Zea mays L.) with a total production of 60 million tons and average yield in the first harvest of 5.4 t ha-1 (Conab, 2016). The average national productivity is considered low, since the industries that operate on a high technological level obtained values three times higher than the average productivity presented for the same harvest. Several technologies, including the use of herbicides and toxic proteins, help increase agricultural productivity. There are consequences linked to technologies use, such as the different effects on non-target organisms (Rosa et al, 2010). Bees play an important role in plant production, which are secondary targets of the effects of chemicals. Several researchers in the laboratory and in the field have attempted to evaluate and determine the effect of herbicides on bees (Chambó et al, 2010). Reductions and delays of plant flowering is caused by herbicide lesions that can disrupt pollinator communities (Bohnenblust et al, 2016). Bees exploit floral sources of pollen and nectar influenced by the selection pressure of the environment, noting that environmental contaminants and the time that food sources remain available for the visitor are fundamental variables (Brizola-Bonacina et al, 2012)
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