Spatial and temporal variability in host use by Helicoverpa zea as measured by analyses of stable carbon isotope ratios and gossypol residues

1. A high dose/refuge strategy has been adopted in the USA to manage the risk of Bacillus thuringiensis (Bt) resistance in target pests such as the cotton bollworm (CBW), Helicoverpa zea (Boddie) in transgenic Bt cotton Gossypiwn hirsutum L. Structured refuges, consisting of non-Bt cotton, have been...

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Published in:The Journal of applied ecology 2010-06, Vol.47 (3), p.583-592
Main Authors: Head, Graham, Jackson, Ryan E., Adamczyk, John, Bradley, Julius R., Van Duyn, John, Gore, Jeff, Hardee, Dick D., Leonard, B. Rogers, Luttrell, Randall, Ruberson, John, Mullins, J. Walt, Orth, Robert G., Sivasupramaniam, Sakuntala, Voth, Richard
Format: Article
Language:English
Subjects:
Animal, plant and microbial ecology
Applied ecology
Bacillus thuringiensis
Biological and medical sciences
Bollworms
Carbon
Carbon isotopes
Corn
Cotton
cotton bollworm
Ecology
Fundamental and applied biological sciences. Psychology
General aspects
Gossypium hirsutum
Helicoverpa zea
insect resistance management
Isotopes
Larvae
Larval development
Moths
Pest control
Pests
refuge
Resistance to control
Sorghum
Transgenic plants
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Summary:1. A high dose/refuge strategy has been adopted in the USA to manage the risk of Bacillus thuringiensis (Bt) resistance in target pests such as the cotton bollworm (CBW), Helicoverpa zea (Boddie) in transgenic Bt cotton Gossypiwn hirsutum L. Structured refuges, consisting of non-Bt cotton, have been a mandated part of this strategy to produce non-selected insects that are temporally and spatially synchronous with insects from the Bt crop, diluting Bt resistance alleles through mating. However, the bollworm is highly polyphagous and exploits a large number of crop and weedy hosts concurrently with Bt cotton. 2. A study was carried out in five major US cotton-producing states during 2002 and 2003 using the ratios of ¹³C to ¹²C in bollworm moths to estimate the proportions of the population originating from C₃ or C₄ plants. A separate study measured gossypol residues in moths from four states in 2005 and 2006, enabling the identification of moths whose natal hosts were cotton rather than other C₃ hosts. 3. C₄ hosts served as the principal source of bollworm moths from mid-to-late June to early September, depending on the state. Beginning in late August/early September and lasting 1-4 weeks, the majority of moths exhibited isotopic compositions characteristic of C₃ hosts. During this period, however, the minimum percentage of moths that developed as larvae on C₄ hosts was typically > 25%. By mid-September and through October and November, the majority of the bollworm population exhibited C₄ isotopic compositions. 4. Between late June and early August, cotton-derived bollworm moths (moths with gossypol residues) comprised < 1% of moths in all states, and remained below this level throughout the season in North Carolina. In other states, cotton-derived moths increased between early August and early September to peak at an average of 19·1% of all moths. 5. Synthesis and applications. Data on ¹³C/¹²C ratios and gossypol residues in CBW moths were used to assess the importance of structured non-Bt cotton refuges for the management of Bt resistance risk in H. zea. Weekly estimates of bollworm breeding on cotton, C₃ plants other than cotton and C₄ plants showed that, throughout the season, the majority of bollworm moths caught in pheromone traps adjacent to cotton fields did not develop as larvae on cotton. This result implies that management practices in cotton such as the use of structured cotton refuges will play a relatively minor role - particularly compared wit
ISSN:0021-8901
1365-2664
DOI:10.1111/j.1365-2664.2010.01796.x