Evaluation of fungicides for the control of Rhizoctonia stem rot on garden mum, 2011

摘要

The purpose of this study was to test the experimental fungicide CGA173506, a wettable granular formulation of Hurricane, for control of Rhizoctonia stem rot. Fifty rooted ‘Goldcrest Yellow’ chrysanthemum cuttings were planted in 6-in. azalea pots containing custom Fafard Growing Mix 1-P (Fafard, Agawam, MA) on 25 and 26 May. Plants were grown in a poly-covered greenhouse with 70°F day and 60°F nights and were watered to saturation as necessary. Ten single-plant replicates, per treatment, were arranged in a randomized complete block on a greenhouse bench. On 27 May, Hurricane and CGA173506 were applied as sprenches (4 fl oz per pot) using a handheld sprayer. Plants were inoculated 14 days after the fungicide application by placing two grains ofwhite rice, colonized with Rhizoctonia solani, 0.75-in. from the crown of each plant and lightly watering each plant to increase the relative humidity beneath the canopy. Topsin M was applied as a sprench when the first symptoms of stem discoloration were observed on 24 Jun and was re-applied on 4 Jul. Plants were rated 8, 22 Jul, and 5 Aug for the percentage of the canopy displaying foliar symptoms including wilting and browning of leaves on a discrete stem, or stems, with corresponding rot at the soilline.