|SCHWARTZ, HOWARD - Colorado State University|
|Gent, David - Dave|
|FICHTNER, SCOTT - Western Farm Service|
|OTTO, KRIS - Colorado State University|
|BOATENG, CHARLES - Colorado State University|
|SZOSTEK, STEPHANIE - Colorado State University|
|CRANSHAW, WHITNEY - Colorado State University|
|MAHAFFEY, LINDA - Colorado State University|
Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2014
Publication Date: 12/31/2014
Citation: Schwartz, H.F., Gent, D.H., Fichtner, S.M., Otto, K., Boateng, C., Szostek, S., Cranshaw, W., Mahaffey, L. 2014. Thrips tabaci (Thysanoptera: Thripidae) and Iris yellow spot virus associated with onion transplants, onion volunteers, and weeds in Colorado. Southwestern Entomologist. 39(4):691-704.
Interpretive Summary: Onion thrips are one of the most important pests of onion. Onion thrips may vector Iris yellow spot virus, which is an emerging disease of increasing important worldwide. In this research, we sampled onion transplants produced in the southwestern U.S. and found that transplants may arrive to other onion production regions contaminated with both thrips and Iris yellow spot virus. We also found that volunteer onion and various weeds commonly found in and around onion fields may be a source of both thrips and the virus. Confirmation that Iris yellow spot virus and viruliferious thrips overwintered in volunteer onions, and some common winter annual and perennial weeds emphasize that volunteer onion and weed management are important components of management of iris yellow spot, in addition to planting transplants free of thrips and the pathogen.
Technical Abstract: Thrips tabaci infestation was determined on onion transplants received in Colorado during March and April from out of state sources (Imperial Valley, near Phoenix Arizona, and southern Texas) during 2004 to 2008. In the five years of the study, 50% to 100% of the transplant lots sampled were found to arrive infested with thrips. Among infested transplant lots, the overall numbers of thrips averaged between 0.15 to 0.63 thrips/plant, with infestations in some lots up to 4 thrips/plant. Thrips tabaci (Lindeman) was the dominant thrips species found in all seasons and locations of transplant origin. In addition, 19 of 83 (23%) tested lots had plants determined to be positive for Iris yellow spot virus (IYSV). IYSV and T. tabaci were detected in volunteer onion plants as early as May 1, a few weeks after the summer onion crop was planted, suggesting a possible role of infected volunteer plants in perennation of the virus between onion crops. IYSV and T. tabaci were detected in many common weeds in and near onion fields including blue mustard (Chorispora tenella), common purslane (Portulaca oleracea), field bindweed (Convolvulus arvensis), flixweed (Descurania sophia), prickly lettuce (Lactuca serriola), and redroot pigweed (Amaranthus retroflexus), collected during early spring near onion fields in Colorado during 2006 to 2009. Confirmation that IYSV and IYSV-infective thrips overwintered in volunteer onions, and some common winter annual and perennial weeds emphasize that volunteer onion and weed management are important components of management of iris yellow spot, in addition to planting transplants free of thrips and the pathogen.