Evaluation location: Colorado, United States
Rhizoctonia root rot done by Earl Ruppel and Lee Panella at Fort Collins, Colorado 1997. One-row plots, planted in mid-May, were 4.3 m (14 feet) long with 56 cm (22 inches) between rows and 20- to 25-cm (8-10 inches) within-row spacing in 5 replications. Fertilization and weed control were based normal growing practices. Plots were thinned to 8 in spacing between beets starting about 6 wk after planting. Stand counts were made on all plots the week before inoculation and inoculation with dry, ground, barley-grain inoculum (3.0 g m-1) of Rhizoctonia solani isolate R-9 was performed on July 10th. Immediately after inoculation, a cultivation was performed to throw soil into the beet crowns. Beets were harvested on August 20th and 21st. Each root was rated for rot on a scale of 0 to 7 (no rot to dead), and plot means for disease index were calculated. These were transformed to a 1 to 9 scale for reporting here. Ample rainfall early in the season, followed by protracted high temperatures and more heavy rain in July and August, led to an extremely severe root rot epidemic in our 1997 nursery. Mean DIs across all tests this year for the highly resistant, resistant, and highly susceptible controls were 3.8, 4.2, and 6.5, respectively. Data was taken on a 0-7 scale and adjusted to the 0-9 scale by multipling by 1.3.