Mary K. Corp

Trap Response of Dargida terrapictalis (Buckett) (Lepidoptera: Noctuidae) to a Sex Attractant in Wheat-Growing Areas of Eastern Washington and Neighboring Oregon

Abstract Traps in eastern Washington and northeast Oregon wheat fields, baited with a sex attractant for the moth of the wheat head armyworm Dargida diffusa (Walker), captured the congener moth Dargida terrapictalis (Buckett). When the two components of a sex attractant for the wheat head armyworm were tested singly versus together in a trap, nearly all D. terrapictalis captured were in traps baited with the combination of (Z)-11-hexadecenyl acetate and (Z)-11-hexadecenal, indicating synergy of the two compounds as attractants. Traps baited with this sex attractant and maintained through the growing season captured D. terrapictalis primarily in May in Umatilla County, Oregon, and in June and early July in eastern Washington. Small numbers of D. diffusa were present also in these traps, largely coincident in time with D. terrapictalis captured. This is the first demonstration of a sex attractant for D. terrapictalis and confirms the presence of D. diffusa in the states of Oregon and Washington through the identification of trapped moths.

Categorization of Putative Factors Against Rhopalosiphum padi (L.) (Heteroptera: Aphididae)

Abstract The bird cherry-oat aphid, Rhopalosiphum padi (L.) (Heteroptera: Aphididae), causes heavy losses to wheat crops worldwide by direct damage and virus transmission. This study was conducted to identify putative resistance mechanisms in four wheat varieties (Bobtail, Ladd, Stephens, and Skiles) and one advanced line (YS434) where R. padi was subjected to choice and no-choice tests. Antixenosis, antibiosis and tolerance studies were conducted in controlled environmental conditions at temperature of 20 ± 5°C, 50–65% RH, and a photoperiod of 14:10 (L:D) h. Based on the antixenosis test, the variety Skiles was found susceptible to R. padi, while the line YS434 showed a significant level of resistance; the varieties Bobtail, Ladd, and Stephens showed intermediate response. In the antibiosis experiment, R. padi produced less progeny on the variety Skiles as compared with other varieties, but the developmental time for nymphs was also significantly shorter on Skiles and recorded higher intrinsic rate of natural increase (rm) values as compared with the varieties YS434, Bobtail, and Ladd. In the tolerance tests, the variety Ladd showed significantly lower tolerance index value than YS434, followed by Skiles, Bobtail, and Stephens. The plant resistance index value was greater for the variety Ladd, followed by Stephens, YS434, and Bobtail. In conclusion, this study provides baseline information that will contribute to the identification of putative resistance factors for a future breeding program against this aphid.

One-pass Tillage for Summer Fallow Under Arid Summer Conditions

Millions of acres of cropland with as low as 6 inches annual precipitation are used for production of winter wheat (Triticum aestivum L.) in the Pacific Northwest of the USA. Despite soil conservation advances, soil erosion continues to be a problem. This on-farm study analyzed seed-zone soil water under farmerimplemented fallow tillage practices to find out if very low-disturbance systems are possible. A low-disturbance, wide-blade undercutter sweep treatment was similar or superior to the farmer’s more intensive conventional tillage system. A subsequent test at four paired no-till-conventionally-tilled summer-fallow sites demonstrated that a single pass of an undercutter sweep in the no-till field could preserve seed-zone moisture comparable to the more intensive multiple-pass conventional tillage. Despite conventional wisdom, summer-fallow soil mulches do not need to be finely pulverized or repeatedly tilled to be effective.