Evaluation location: Idaho, United States
The curly top evaluation was conducted at the USDA-ARS North Farm in Kimberly, ID which has Portneuf silt loam soil and had been in barley in 2010. The field was plowed both in the fall and the spring, fertilized (80 lb N and 120 lb P2O5/A) on 20 Apr 11, sprayed with Ethotron (2 pt/A), and roller harrowed. The germplasm was planted (density of 142,560 seeds/A) on 16 May. The plots consisted of two rows 10 ft long with 22-in row spacing, arranged in a randomized complete block design with two replicates. The field was sprinkler irrigated and hand-weeded as necessary. Plant populations were thinned to about 47,500 plants/A on 19 June. Plants were inoculated at the four to six leaf growth stage on 27 June with approximately six viruliferous beet leafhoppers per plant. The leafhoppers had been reared in the greenhouse on viruliferous sugar beet plants. The beet leafhoppers were moved twice a day (right after sunrise and just before sunset) for 1 week by dragging a tarp through the field. The plants were sprayed with Lorsban 4E (1.5 pints/A) on 11 July to kill the beet leafhoppers. The plots were rated for foliar symptom development on 18 July using a scale of 0-9 (0 = healthy and 9 = dead; Mumford 1974). Curly Top development was uniform and no other disease problems were evident in the plot area. The test was evaluated while disease pressure was moderate and good symptom development occurred in the more susceptible lines. The experiment was rated only 3 weeks after inoculation, because of the severity of the epidemic; some of the more susceptible entries had died by 4 weeks and thus some of the differences among entries were no longer apparent.