Field Evaluation of Bt Cotton Crop Impact on Nontarget Pests: Cotton Aphid and Boll Weevil

Abstract

Bt cotton plants expressing Cry1Ac protein have high specificity for the control of lepidopteran larvae. However, studies conducted in several countries have shown these plants have a differential impact on nontarget herbivores. The aim of this study was to compare the colonization rates and population abundance of the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) and the boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae), in plots of Bt (Nuopal) and non-Bt cotton (Delta Opal) in an experimental field in Brasilia, DF, Brazil. No difference was observed in the preference and colonization by winged aphids to plants from the two treatments. There was no significant difference in abundance of wingless aphids or in the production of winged aphids between treatments. Apparently, the parameters that control factors such as fecundity, survival, and dispersal were similar on both Bt and non-Bt plants. Monitoring of plants for coccinellids, a specialist predator of aphids, and ants that act on the dispersal of aphids among plants showed no significant difference between Bt and non-Bt plants, supporting the inference above. Regarding the effect on boll weevil, there was also no significant difference between treatments in the total number of fruiting structures attacked in each plot, the percentage of fruiting structures attacked per plant or on the number of weevils emerging from fruits with boll weevil damage from egg-laying, when damaged fruit samples were held in the laboratory. Based on these results, we conclude that there is no impact of Bt cotton crop expressing Cry1Ac on the nontarget herbivores tested under field conditions.

Effects of Soil Water Deficit on Insecticidal Protein Expression in Boll Shells of Transgenic Bt Cotton and the Mechanism

“…Although Bollgard II ® varieties containing the additional δ-endotoxin of Bacillus thuringiensis , Cry2A (b), have been employed in both Australia and the United States ( Morse, 2016 ), the single toxin Bt-cotton (Bollgard I) has dominated domestic production in Asia and Africa ( Huang et al, 2010 ; Clive, 2012 ). People still use the single toxin Bt-cotton, expressing its own insecticidal protein, to effectively reduce losses to pests such as cotton boll worm ( Sujii et al, 2013 ), and to reduce pesticide use in those countries. The use of Bt-cotton produces dramatic economic and ecological benefits ( Dhillon and Sharma, 2013 ).…”

The impact of secondary pests on Bacillus thuringiensis (Bt) crops

“…Adopting farmers are either still using significant numbers of insecticide applications to control secondary pests, or the damage caused by these pests has increased. Some examples include South Africa (Hofs et al ., ; Schnurr, ), Burkina Faso (Dowd‐Uribe, ), Pakistan (Jaleel et al ., ), Australia (Wilson et al ., ), Brazil (Sujii et al ., ) and Mexico (Traxler and Godoy‐Avila, ).…”

Arthropod food webs associated with cotton: Does Bt cotton mediate community stress?

“…The efficacy of this technology is high against some of these species, and Bt resistance is a frequent concern in such a scenario receiving considerable attention (Santos‐Amaya et al., 2017; Siegfried & Jurat‐Fuentes, 2016; Sorgatto et al., 2015). Bt non‐target species also received attention, and negligible effects prevail in different regions (Duan et al., 2008; Lima et al., 2013; Nascimento et al., 2021; Sujii et al., 2013). However, studies of Bt cotton impact in arthropod assemblages and communities are not as frequent, but again usually report negligible effects on soil (Krogh et al., 2020; Tian et al., 2020)‐ and plant‐associated species (Marvier et al., 2007; Sisterson et al., 2004; Sujii et al., 2013; Torres & Ruberson, 2005), despite their limitations akin to those of pesticide impact assessments (Guedes et al., 2016, 2017).…”