Response of several potato cultivars to metribuzin and diquat

Foliar application of metribuzin resulted in severe foliar injury to potato cultivars Atlantic, Norchip, and Hilite Russet, reduced yields for Butte, Norchip, and Hilite and had no effect on AC Novachip, NorWis, Century Russe t, Frontier Russet, and Ranger Russet over 2 yr. Diquat application to 14 c ultivars over a six year period resulted in 73-97% foliar and 63-97% stem d esiccation. Ranger Russet, at 63% had the lowest rating for stem desiccatio n. Tuber sprout weight was not affected, except for the cultivar Shepody, w here it increased when diquat was applied. Application of diquat significan tly increased the amount of tuber stem end discolouration for AC Novachip, Atlantic, Norchip, NorWis, Butte, Century Russet, Frontier Russet, Hilite R usset, and Ranger Russet in one study but levels were very low. The present study was conducted to determine the response of new cultivars to metribuz in, applied either pre-emergence or post-emergence, and to diquat applied e ither at in single or split application, of the maximum labelled rate, and to determine any effect on tuber yield. The results of this study suggest t hat some new cultivars may respond differently to the application of metrib uzin and diquat and their response needs to be determined before use recomm endations are made. (C) 2001 Published by Elsevier Science Ltd.