Alfalfa is a cornerstone of the agricultural economy of the pacific northwest, with idaho ranking first in U.S. Production annually

The Department of Agriculture National Institute of Food and Agriculture awarded the Regents of the University of Idaho $548,008 on September 1, 2026, under the Alfalfa Seed and Alfalfa Forage Systems Program (CFDA 10.330) to evaluate integrated pest management strategies for aphid-vectored viruses in alfalfa production.

The project will assess the efficacy of combining selective soft insecticides with mineral crop oils to reduce transmission of alfalfa mosaic virus, bean leafroll virus, and pea streak virus over a full three-year production cycle. The research will characterize virus prevalence in commercial alfalfa fields across Idaho and Oregon, relate infection patterns to production and management practices, and measure effects on aphid vector densities and beneficial arthropod populations. The strategy adapts an approach previously used in seed potato studies, employing mineral crop oils to interfere with aphid probing and virion binding.

Period of performance runs through August 31, 2029, with work performed at Moscow, Idaho. The project addresses a gap in understanding yield and quality effects of pervasive viruses in alfalfa, a cornerstone crop of Pacific Northwest agriculture with Idaho ranking first nationally in production. Results are intended to enhance economic profitability of growers while advancing sustainable integrated pest management practices in the region.

As a perennial crop typically grown for four or more years, alfalfa serves as a sentinel host that accumulates insect-transmitted pathogens over multiple growing seasons. Despite the importance of alfalfa, little is known about yield and quality effects of pervasive, aphid-vectored viruses such as alfalfa mosaic virus (AMV), bean leafroll virus (BLRV), and PEA streak virus (PESV). Our group recently found that conventional insecticides can reduce vector densities, but often fail to reduce virus prevalence or improve forage yield and quality in established stands. This project proposes a novel integrated management strategy combining selective soft insecticides with mineral crop oils to suppress virus transmission. This approach, successfully used in our seed potato studies, uses mineral crop oils to interfere with aphid probing and virion binding. Our primary objective is to evaluate the efficacy of integrated mineral oil and selective insecticide rotations in reducing virus prevalence, suppressing aphid vector densities, and preserving beneficial arthropods over a full three-year production cycle. We will also characterize the prevalence of AMV, BLRV, and PESV in commercial alfalfa fields in idaho and oregon and relate virus infection to production and management practices. This research will enhance the economic profitability of growers while advancing sustainable integrated pest management strategies for alfalfa production in the pacific northwest.