Crambus cypridalis (Hulst) (Lepidoptera: Crambidae) is widely distributed throughout the western United States (Crawford & Harwood 1964; Powell & Opler 2010). The larvae probably feed on grasses, as do congeneric species (Robinson et al. 2002), but it is not reported as a crop pest.
Monitoring of wheat head armyworm moth Dargida (= Faronta) diffusa (Walker) and the sibling species Dargida (= Faronta) terrapictalis (Buckett) in eastern Washington resulted in serendipitous captures of male C. cypridalis in sex attractant-baited traps (Landolt et al. in press). This result led us to test the hypothesis that C. cypridalis males are attracted to the combination of (Z)-11-hexadecenyl acetate (Z11-16Ac) and (Z)-11-hexadecenal (Z11-16Ald). We also report new information on the seasonal timing of captures of C. cypridalis in sex-attractant traps, which was not included by Landolt et al. (2011).
Chemicals were dispensed from red rubber septa (West Co., Lionville, Pennsylvania) and tested in UniTraps (Agrisense Inc., Pontyprid, United Kingdom) with a 6 cm2 piece of Vaportape® (Hercon Environmental, Emigsville, Pennsylvania) placed within each trap bucket. Traps were attached to stakes at the edges of wheat fields.
In 2009 and in 2010, 31 and 13 traps, respectively, were baited with septa loaded with 1 mg Z11-16Ac plus 100 µg Z11-16Ald for trapping the wheat head armyworm moth (Landolt et al. in press). Of those traps, 16 in 2009 and 13 in 2010 were maintained long enough through the season to capture C. cypridalis. Other traps in that study were withdrawn earlier in Sep in response to the end of captures of Dargida sp. Each trap was placed in a different wheat field in Grant and Lincoln Counties, Washington. We report on captures of C. cypridalis in the 16 traps in 2009 that were maintained from late May through Sep, and on the 13 traps in 2010 that were maintained from the first week of May through Sep. Traps were checked weekly, and lures and Vaportape® were replaced monthly. None of these traps were accompanied by control traps because the objective of the study was to determine the presence of Dargida sp moths, not to test the hypothesis of sex attraction.
A subsequent experiment then tested the hypothesis that C. cypridalis is attracted to the wheat head armyworm sex attractant, and determined if both chemicals are necessary for attraction. Four trap treatments were used: 1) a control with no lure, 2) a septum with 1 mg of Z11-16Ac, 3) a septum with 100 µg of Z11-16Ald, and 4) a septum with the combination of 1 mg Z11-16Ac and 100 µg Z11-16Ald. A randomized complete block experimental design was used with 6 replicate blocks. Each block of traps was placed at a separate wheat field in Grant and Lincoln Counties, Washington. Traps were maintained and checked each wk from 7 Sep to 5 Oct 2010.
Voucher specimens of C. cypridalis were deposited in the M. T. James Entomological Collection of Washington State University, Pullman, Washington.
In 2009, male C. cypridalis were captured in 14 of the 16 traps that were baited with Z11-16Ac plus Z11-16Ald, and that were maintained through Sep (14.2 ± 3.7 males per trap). In 2010 male C. cypridalis were captured in all 13 of the same sex attractant traps (4.8 ± 1.3 males per trap). In both years, all C. cypridalis moths were captured during the last 2 wk of Sep. We do not know when the moth flight ended because these traps were not maintained long enough into Oct.
In experiment 2, most male C. cypridalis were captured in traps baited with Z11-16Ac plus Z11-16Ald (Table 1). None were trapped with Z11-16Ac alone, and only 3 moths were trapped with Z11-16Ald alone. These moths were captured from 14 Sep until 5 Oct, when traps were taken down.
Male C. cypridalis consistently responded to the combination of Z11-16Ac plus Z11-16Ald, with no response to the unbaited traps in the second study, or to either Z11-16Ac or Z11-16Ald alone. This is a first report of an attractant for trapping C. cypridalis, and the second report of a sex attractant for a Crambus sp; Booij and Voerman (1984) captured 25 male Crambus nemorella (Hübner) in traps baited with Z11-16Ac.
Males of the glassy cutworm moth, Apamea devastator (Brace), are also attracted to Z11-16Ac plus Z11-16Ald (Steck et al. 1977; Underhill et al. 1977; Landolt et al. 2011). The glassy cutworm co-occurs in eastern Washington wheat fields with D. diffusa, D. terrapictalis and C. cypridalis. All are attracted to this same combination of chemicals, raising the question of how they might avoid inter-specific sexual interactions. There is a seasonal separation in their flight patterns, which should provide some reproductive isolation among them, with the 2 Dargida species flying in late spring (May/Jun) (Landolt et al. 2011), the glassy cutworm flying in summer (July/Aug), and C. cypridalis flying in early autumn (Sep/Oct). There may be additional chemicals present in the female sex pheromones of these moths that contribute to reproductive isolation. Steck et al. (1977) indicated a role of (Z)-7-dodecenyl acetate in sex attraction of C. devastator, as well as Z11-16Ac and Z11-16Ald. There are no reports however of characterization of pheromones produced or emitted by females of any of these 4 moth species.
MEAN NUMBERS OF MALE CRAMBUS CYPRIDALIS CAPTURED IN TRAPS BAITED WITH THE SEX ATTRACTANT COMPOUNDS Z11-16AC AND Z11-16ALD. GRANT AND LINCOLN COUNTY, WASHINGTON, SEP 2010.
The late season capture of male C. cypridalis in sex attractant traps in 2009 and 2010 is not consistent with other reports of the seasonality of occurrence of the adult. Powell & Opler (2010) indicate that this moth flies in mid summer; and Crawford & Harwood (1964) reported the flight of the same species in late summer. Perhaps the moth flight period varies with latitude and altitude, or there might be unresolved taxonomic issues with this species.
Males of C. cypridalis were consistently captured in traps baited with Z11-16Ac plus Z11-16Ald. The consistent presence of C. cypridalis in eastern Washington wheat fields suggests the possibility that it infests wheat, but additional study is needed to determine its host plant(s), abundance, and any pest significance in this habitat. These moths were trapped in late Sep and early Oct, which differs from prior reports of activity. This report provides a new sex attractant for potential use in monitoring this species, as well as new information on its seasonality and geographic distribution.
Attractant lures were made by Daryl Green and Bonnie Oehler, and traps were maintained and checked by Robin Garcia. This project was supported in part by funding from the Washington Wheat Commission provided to Washington State University. The identity of C. cypridalis was confirmed by Dr. Alma Solis, Systematic Entomology Laboratory, ARS, USDA, Beltsville, Maryland and U.S. National Museum, Washington, DC. USDA is an equal opportunity provider and employer.