Evaluation location: Idaho, United States
In 2008, the USDA-ARS sugarbeet program in Kimberly, ID, in cooperation with the BSDF created an artificial curly top epiphytotic through the release of viruliferous leafhoppers at the USDA-ARS North Farm in Kimberly, ID. The Curly Top Nursery was conducted at the USDA-ARS North Farm, which had been in beans in 2008. The field was plowed in the fall, fertilized (75 lb N/A and 75 lb P2O5/A) on April 22, 2009, sprayed with Ethotron (2 pt/A), and roller harrowed. The field was planted (density of 142,560 seeds/A) on May 18 in two row plots 10 ft long and 22 in row with two replicates in a randomized complete block design. The fields were sprinkler irrigated and hand weeded as necessary. The plant populations were thinned to 47,520plants/A. The plants were inoculated at the 4-6 leaf growth stage on June 23 with 6 viruliferous beet leafhoppers per plant. The beet leafhoppers were moved twice a day (right after sunrise and just before sunset) for one week. The plants were sprayed with Lorsban 4E (1.5 pints/A) on July 7 to kill the beet leafhoppers. The plots were rated for symptom development using a scale of 0-9 (0 = healthy and 9 = dead; described in Plant Disease 91:1459-1463). Disease development was very good at both sites allowing for good separation on all rating dates and data from the last (July 27), most severe rating were used. The temperatures were below normal early in the growing season but warmed up around beet leafhopper release.