The response of female boll weevils to males, Anthonomus grandis Boheman, in laboratory bioassays can be reproduced by exposure to a mixture of compounds I, II, and either III or IV, all isolated from male weevils and their fecal material. The same response was elicited by mixtures of tile synthesized coimpounds. Compound I is (+)-cis-2-isopropenyl-l-methylcyclobtutaneethanol; II, cis-3,3-dimethiyl->(1,beta)cyclohexaneethanol; III, cis-3,3-dimethlyl->(1,alpha)-cyclohexaneacetaldehyde; and IV, trans-3,3-dimethyl->(1,alpha)-cyclohexanecetaldehyde.

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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 Gossypium 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 13 C to 12 C in bollworm moths to estimate the proportions of the population originating from C 3 or C 4 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 C 3 hosts. 3. C 4 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 C 3 hosts. During this period, however, the minimum percentage of moths that developed as larvae on C 4 hosts was typically >25%. By mid-September and through October and November, the majority of the bollworm population exhibited C 4 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 19AE1% of all moths. 5. Synthesis and applications. Data on 13 C ⁄ 12 C 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, C 3 plants other than cotton and C 4 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 with maize Zea mays L. -in managing potential resistance to Bt cotton in populations of the CBW in the US Cotton Belt.

Selection pressure on bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), by cotton, Gossypium hirsutum (L.) (Malvaceae), that produces one or more Bacillus thuringiensis Berliner (Bt) proteins is reduced by plantings of non‐Bt refuge cotton that produce non‐selected individuals. However, the contributions of non‐Bt, non‐cotton crop hosts to the overall effective refuge for H. zea on Bt cotton have not been estimated. A 2‐year, season‐long study was conducted in five US cotton‐producing states to assess the spatial and temporal population dynamics and host use of H. zea. Helicoverpa zea larval estimates in commercial crop fields demonstrated that non‐cotton crop hosts, such as maize, Zea mays L. (Poaceae), grain sorghum, Sorghum bicolor (L.) Moench (Poaceae), peanut, Arachis hypogaea L. (Fabaceae), and soybean, Glycine max (L.) Merrill (Fabaceae), collectively support much larger larval populations than cotton throughout the season. Larval populations were almost entirely restricted to maize in the middle part of the season (June and portions of July), and were observed in non‐cotton crop hosts more frequently and typically in larger numbers than in cotton during the period when production would be expected in cotton (July and August). Numbers of H. zea larvae produced in replicated strip trials containing various crop hosts paralleled production estimates from commercial fields. In contrast, the number of H. zea adults captured in pheromone traps at interfaces of fields of Bt cotton and various crop hosts rarely varied among interfaces, except in instances where maize was highly attractive. With the exception of this early season influence of maize, moth numbers were not related to local larval production. These data demonstrate that H. zea adults move extensively from their natal host origins. Therefore, non‐cotton crop hosts, and even relatively distant hosts, contribute significantly to effective refuge for H. zea on Bt cotton. The results presented here demonstrate that substantial natural refuge is present for Bt‐resistance management of H. zea throughout the mid‐South and Southeast portions of the US cotton belt.