Pest Management Science (2016) 72, 1727-1736

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Celso Omoto, Oderlei Bernardi, Eloisa Salmeron, Rodrigo J. Sorgatto, Patrick M. Dourado, Augusto Crivellari, Renato A. Carvalho, Alan Willse, Samuel Martinelli and Graham P. Head (2016)
Field-evolved resistance to Cry1Ab maize by Spodoptera frugiperda in Brazil
Pest Management Science 72 (9), 1727-1736
Abstract:
BACKGROUND
The first Bt maize in Brazil was launched in 2008 and contained the MON 810 event, which expresses Cry1Ab protein. Although the Cry1Ab dose in MON 810 is not high against fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), MON 810 provided commercial levels of control. To support insect resistance management in Brazil, the baseline and ongoing susceptibility of FAW was examined using protein bioassays, and the level of control and life history parameters of FAW were evaluated on MON 810 maize.
RESULTS
Baseline diet overlay assays with Cry1Ab (16 µg cm-2) caused 76.3% mortality to field FAW populations sampled in 2009. Moderate mortality (48.8%) and significant growth inhibition (88.4%) were verified in leaf-disc bioassays. In greenhouse trials, MON 810 had significantly less damage than non-Bt maize. The surviving FAW larvae on MON 810 (22.4%) had a 5.5 day increase in life cycle time and a 24% reduction in population growth rate. Resistance monitoring (2010–2015) showed a significant reduction in Cry1Ab susceptibility of FAW over time. Additionally, a significant reduction in the field efficacy of MON 810 maize against FAW was observed in different regions from crop season 2009 to 2013.
CONCLUSIONS
The decrease in susceptibility to Cry1Ab was expected, but the specific contributions to this resistance by MON 810 maize cannot be distinguished from cross-resistance to Cry1Ab caused by exposure to Cry1F maize. Technologies combining multiple novel insecticidal traits with no cross-resistance to the current Cry1 proteins and high activity against the same target pests should be pursued in Brazil and similar environments.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Celso Omoto, Oderlei Bernardi, Graham Head, Samuel Martinelli

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
resistance/tolerance/defence of host

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.


Spodoptera frugiperda Maize/corn (Zea mays)
Bacillus thuringiensis genes in crops (entomopathogen) Spodoptera frugiperda Maize/corn (Zea mays)
Bacillus thuringiensis Cry1A-toxin (entomopathogen) Spodoptera frugiperda Maize/corn (Zea mays)
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