Re-evaluating the Economic Injury Level for Alfalfa Weevil (Coleoptera: Curculionidae) Control in Low Desert Irrigated Alfalfa

• Published in: Journal of economic entomology Vol. 114; no. 3; pp. 1173 - 1179
• Main Authors: Harrington, K., Carrière, Y., Mostafa, A. M.
• Format: Journal Article
• Language: English
• Published: US Entomological Society of America 01.06.2021; Oxford University Press
• Subjects: Agricultural economics; Agricultural production; Alfalfa; Alfalfa weevil; Communication; Cropping systems; Crops; Deserts; Economic aspects; economic injury level; economic threshold; Entomology; FIELD AND FORAGE CROPS; Hypera brunneipennis; Hypera postica; Insecticides; integrated pest management; Larvae; Medicago sativa; Arizona; California; United States > US; economic threshold; economic injury level; Alfalfa weevil; integrated pest management
• ISSN: 0022-0493; 1938-291X
• DOI: 10.1093/jee/toab070

Alfalfa (Medicago sativa L.) dominates cropping systems in the Western United States and is first in terms of acreage planted in Arizona. The alfalfa weevil, Hypera postica (Gylenhall) and/or Hypera brunneipennis (Boheman), respectively, is the most destructive pest in terms of yield loss in low desert-grown alfalfa hay. The current economic threshold of 15–20 larvae per sweep, established in California in 1975, is currently not suitable or adopted by growers in the western U.S. low desert. Here, we conducted 4 yr of field trials to re-evaluate this economic threshold. Supporting observations of agricultural growers and professionals in the region, our results indicate that the economic threshold established in 1975 is too high. Specifically, one to three large larvae often cause a significant decrease in yield justifying weevil control based on current hay prices and costs of insecticide application. These results are discussed in the context of sustainable alfalfa production in the western U.S. low desert.