INFLUENCES OF THE RHIZOCTONIA DISEASE ON PRODUCTION OF THE RUSSET BURBANK POTATO

Pentachloronitrobenzene (PCNB) treatment (20 lb/A - 22.4 kg/ha) showed significant reduction of Rhizoctonia (Rhizoctonia solani Kühn) symptoms on potato. The PCNB treatment increased the number of non-girdled stolons as compared to untreated plots by 50, 34, and 30% at respective seedpiece spacings of 6, 9, and 12 in (15, 23, and 30 cm). Numbers of non-girdled stolons in PCNB-treated plots at 9- and 12-in spacing did not differ significantly from those in untreated plots at 6-in spacing. Yield differences (either total or U.S. #1) among treatments were not observed, but size differences were evident. Closer spacing or PCNB treatment or both increased the number of small U.S. #1 potatoes and decreased the number of large U.S. #1 potatoes (over 7 oz. - 199 g). Although the number of smaller potatoes was increased by 27% with PCNB treatment, the percentage of malformed tubers was reduced by 50%. Tuber size was reduced as the number of non-girdled stolons was increased (P =.001). Results suggest that Rhizoctonia control may benefit the fresh potato packer and seedgrower by potentially reducing seed requirement/acre, by increasing capacity for single-drop seed production, and by greater control over U.S. #1 size. © 1979 Springer.