Evaluation of fungicides at different application intervals for the control of powdery mildew of dogwood, 2018

摘要

Flowering dogwood (Cornusflorida) cultivar Cherokee Princess seedlings were potted in no. 1 nursery containers in Morton's no. 2 Grow Mix on 15 May. Each plant was top-dressed with 0.5 oz of 18-6-12 Osmocote Classic controlled release fertilizer on 1Jun. Four single-plant replications per treatment were arranged in a randomized complete block design in a greenhouse at the Otis L. Floyd Nursery Research Center in McMinnville, TN. Flowering dogwood plants were watered twice per day using an overhead irrigation system. Treatments were applied to run-off using a backpack CO2-pressurized sprayer at 40 psi on a 14- or 21-day interval. Control plants were sprayed with water. The severity of powdery mildew was evaluated on 14, 21 and 28 Jun, and on 5, 12 and 19 Jul using a scale of 0-100% foliage area affected, and the area under the disease progress curve (AUDPC) was calculated. Plant quality was evaluated on the same dates using a scale of 1-9 where 1 is dead, 7 is commercially acceptable, and 9 is a perfect plant. Plant height and width were measured on 19 Jul. Average maximum temperatures for 14-30 Jun and 1-19 Jul were 81.2 and 83.0°F, respectively; average minimum temperatures were 59.5 and 58.9°F, respectively. Analysis of variance was performedusing the general linear models procedure with SAS statistical software and means were separated using Fisher's least significant difference test.