Monitoring the Evolution of Resistance in Spodoptera frugiperda (Lepidoptera: Noctuidae) to the Cry1F Protein in Argentina.

Maize (Zea mays L.) is one of the most important and widely cultivated crops in Argentina. Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is a common maize pest capable of causing significant yield losses and is most destructive in late-planted maize in subtropical regions, going through five to six generations per growing season. The Bacillus thuringiensis (Bt) trait Herculex I Insect Protection technology by Dow AgroSciences and Pioneer Hi-Bred (HX I, event DAS-Ø15Ø7-1), expressing Cry1F protein, was launched in the 2005-2006 season in Argentina and was widely adopted because of the high level of efficacy against S. frugiperda, as well as other pests such as Diatraea saccharalis (J.C. Fabricius). However, increased late-season plantings, limited adoption of refuge, and properties of S. frugiperda biology (high number of generations and migratory behavior) have led to high S. frugiperda exposure to Cry1F and resistance selection pressure. Field efficacy monitoring has been conducted throughout the main maize production areas in Argentina from 2009 to 2016. Laboratory monitoring has been conducted throughout the same areas from 2010 to 2015. Here, we describe changes in field efficacy of HX I and the results of laboratory-based susceptibility monitoring conducted using purified Cry1F protein. Increases in larval survival and crop damage were evident throughout the 2012-2016 period and spanned the majority of maize production areas in Argentina. Over the same period, random larval collections showed increasing survivorship on diet containing purified Cry1F protein. These field and laboratory studies confirmed that resistance to Cry1F has developed and is now widely distributed in S. frugiperda populations in Argentina.

Impact of transgenic soybean expressing Cry1Ac and Cry1F proteins on the non-target arthropod community associated with soybean in Brazil.

Field-scale studies that examine the potential for adverse effects of Bt crop technology on non-target arthropods may supplement data from laboratory studies to support an environmental risk assessment. A three year field study was conducted in Brazil to evaluate potential for adverse effects of cultivating soybean event DAS-81419-2 that produces the Cry1Ac and Cry1F proteins. To do so, we examined the diversity and abundance of non-target arthropods (NTAs) in Bt soybean in comparison with its non-Bt near isoline, with and without conventional insecticide applications, in three Brazilian soybean producing regions. Non-target arthropod abundance was surveyed using Moericke traps (yellow pan) and pitfall trapping. Total abundance (N), richness (S), Shannon-Wiener (H'), Simpson's (D) and Pielou's evenness (J) values for arthropod samples were calculated for each treatment and sampling period (soybean growth stages). A faunistic analysis was used to select the most representative NTAs which were used to describe the NTA community structure associated with soybean, and to test for effects due to the treatments effects via application of the Principal Response Curve (PRC) method. Across all years and sites, a total of 254,054 individuals from 190 taxa were collected by Moericke traps, while 29,813 individuals from 100 taxa were collected using pitfall traps. Across sites and sampling dates, the abundance and diversity measurements of representative NTAs were not significantly affected by Bt soybean as compared with non-sprayed non-Bt soybean. Similarly, community analyses and repeated measures ANOVA, when applicable, indicated that neither Bt soybean nor insecticide sprays altered the structure of the NTA communities under study. These results support the conclusion that transgenic soybean event DAS-81419-2 producing Cry1Ac and Cry1F toxins does not adversely affect the NTA community associated with soybean.

Evaluation of SmartStax and SmartStax PRO maize against western corn rootworm and northern corn rootworm: efficacy and resistance management.

BACKGROUND: Cases of western corn rootworm (WCR) field-evolved resistance to Cry3Bb1 and other corn rootworm (CRW) control traits have been reported. Pyramid products expressing multiple CRW traits can delay resistance compared to single trait products. We used field studies to assess the pyramid CRW corn products, SmartStax (expressing Cry3Bb1 and Cry34Ab1/Cry35Ab1) and SmartStax PRO (expressing Cry3Bb1, Cry34Ab1/Cry35Ab1 and DvSnf7), at locations with high WCR densities and possible Cry3Bb1 resistance, and to assess the reduction in adult emergence attributable to DvSnf7 and other traits. Insect resistance models were used to assess durability of SmartStax and SmartStax PRO to WCR resistance. RESULTS: SmartStax significantly reduced root injury compared to non-CRW-trait controls at all but one location with measurable WCR pressure, while SmartStax PRO significantly reduced root injury at all locations, despite evidence of Cry3Bb1 resistance at some locations. The advantage of SmartStax PRO over SmartStax in reducing root damage was positively correlated with root damage on non-CRW-trait controls. DvSnf7 was estimated to reduce WCR emergence by approximately 80-95%, which modeling indicated will improve durability of Cry3Bb1 and Cry34Ab1/Cry35Ab1 compared to SmartStax. CONCLUSION: The addition of DvSnf7 in SmartStax PRO can reduce root damage under high WCR densities and prolong Cry3Bb1 and Cry34Ab1/Cry35Ab1 durability. © 2017 Society of Chemical Industry.