Project Number: 8010-22000-032-002-I
Project Type: Interagency Reimbursable Agreement
Start Date: Apr 1, 2022
End Date: Mar 30, 2023
Wheat and barley are major crops in the US that together have annual values during the last decade of $9-19 billion from 49-63 million acres planted. The Russian wheat aphid, Diuraphis noxia (Hemiptera: Aphididae), invaded the US from Eurasia in 1986, spread to 17 western states, and became a major pest of wheat and barley, infesting up to 2 million acres and costing up to $274 million per year. The Russian wheat aphid is seldom a pest in Eurasia, where parasites and predators limit its abundance. However, native parasites and predators in the US had little impact on the Russian wheat aphid during its invasion. Aphelinus (Hymenoptera: Aphelinidae) species are among the most important Eurasian parasites of the Russian wheat aphid. Aphelinus atriplicis, collected in the Caucasus region of southern Russia, was introduced into the US in 1991 and has since become a major natural enemy of this aphid. Nonetheless, the aphid remains a sporadic pest, and Aphelinus hordei, a parasite of the Russian wheat aphid in Europe with a narrow host range, is a promising candidate for introduction. The North American Plant Protection has approved a petition for its release to control this pest, and APHIS-PPQ has issued an Environmental Assessment and Finding of No Significant Impact. ARS expects to receive an APHIS-PPQ permit for field release in Colorado soon. In this project, the objective is to control the Russian wheat aphid in wheat fields in Colorado by releasing Aphelinus hordei. This control would significantly reduce control costs for the Russian wheat aphid, as well as greatly reduce environmental impacts.
ARS will rear Aphelinus hordei in several subcultures that will be maintained at a population size >200 with about equal number of females and males. Parasitoids will be reared on the Rusian wheat aphid on wheat in plant-growth chambers at 20oC and 16:8 h (L:D) photoperiod. Every generation, ARS will put ~200 parasitoids into each cage enclosing potted plants with several thousand aphids. Each cage produces several thousand adult parasitoids, and ARS can keep 60 of these cages (>120,000 parasitoids) in a single plant-growth chamber. Initial releases will be done in wheat and barley fields with abundant Russian wheat aphid near Fort Collins, Colorado, and both within-season reproduction and over-wintered establishment will be monitored. ARS will monitor wheat fields at the release sites and grasslands near the release sites to determine whether A. hordei has established. ARS will use both morphological and molecular traits to identify any Aphelinus species found during sampling. Once A. hordei has established near Fort Collins, we will extend sampling to cover a greater geographical area.