Survival of Hessian Fly (Diptera: Cecidomyiidae) puparia exposed to simulated hay harvest conditions, location and windrow dying in Washington and California

Authors: Yokoyama, Victoria; Cambron, Sue

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2013
Publication Date: 6/13/2013
Citation: Yokoyama, V.Y., Cambron, S.E. 2013. Survival of Hessian Fly (Diptera: Cecidomyiidae) puparia exposed to simulated hay harvest conditions, location and windrow dying in Washington and California. Journal of Economic Entomology. 106: 1164-1172.

Interpretive Summary: Hessian fly is a regulated pest of concern in hay produced in the western states and exported to foreign markets in Japan and other Asia-Pacific and western Asian countries. Quarantine treatments and strategies are continuously under development to ensure trade partners that Hessian fly would not be accidentally introduced through U.S. hay imports. Hay harvesting procedures such as drying have great potential to kill Hessian fly puparia, the insect stage of concern, but thorough testing was needed to confirm such control. More than 96,000 insects were subjected to drying conditions in environmental chambers in the laboratory, and on location in Washington and California with open air exposures and in windrows of harvested hay. The tests showed that Hessian fly is very susceptible to drying in short periods of time and hay harvesting would largely destroy pests contaminating fields of timothy, alfalfa, and grass hays. The work is made available to trade partners and ensures the continuous shipment of 2.7 to 3 million tons of U.S. hay valued at $675-750 million each year into Japan, Korea, United Arab Emirates, China, Vietnam, and other Asian countries.

Technical Abstract: Hessian fly, Mayetiola destructor (Say), puparia are of regulatory concern in exported hay, and drying after harvest was evaluated as cultural control technique for bales shipped from the western states. A total of 16,836; 31,122; and 48,051 puparia were tested under drying conditions in environmental chambers, open air on location, and hay windrows, respectively, in the Kittitas Valley and East Columbia Basin of Washington and the San Joaquin and Imperial Valleys of California. Puparia were exposed in environmental chambers to conditions on simulated hay harvest dates based on historical weather data in major forage production areas. The rate of adult emergence from puparia exposed to drying for 1-8 d decreased with exposure duration, the later the harvest date, and the further south the location. In open air drying on location for 1-7 d, total percentage of puparia surviving to adults for all exposure days was 0.4 % for 18 June in the Kittitas Valley; 1.2 % for 15 May in the San Joaquin Valley; and 0 % for 16 July in the Imperial Valley, and significantly different between controls and exposure durations. In hay windrow drying for 1-6 d, total percentage of puparia surviving to adults for all exposure days was 5.4 % on 28 June and 24.2 % on 7 September in timothy in the Kittitas Valley; 3.8 % on 28 June in timothy in the East Columbia Basin; 2.2 % on 20 July in alfalfa in the San Joaquin Valley; and 6.3 % on 21 July in Sudan grass in the Imperial Valley. The number of puparia surviving to adults in open air drying and in windrows was significantly different between controls and exposure durations for all test dates and locations. Puparial survival in field tests was related to mild temperatures and high humidities. Hay drying is discussed in relation to a systems approach for quarantine control of Hessian fly in exported hay.