Evaluation of fungicides for the control of downy mildew of impatiens, 2015

摘要

Fungicides alone and in combination were tested for the control of impatiens downy mildew (IDM) at the University of Florida Tropical Research and Education Center in Homestead, FL. The experimental design was a randomized complete block design containing ten single plant replicates per treatment. Plants were grown in a 4-inch pot containing 100% coconut coir fiber in a shadehouse under 73% shade. Plants were fertilized with Osmocote 14-14-14 fertilizer (1 tsp/pot) and watered twice daily using overhead irrigation. There was no visible sign of downy mildew disease when the initial fungicide application was made on 2 Apr. Treatments were applied as foliar sprays to runoff at a volume of 1 fl oz of solution per plant. Plants were not watered for 24-hrfollowing fungicide application. Plants were inoculated with a suspension of Plasmopara obducens sporangia (1 x 106 sporangia/ml). Inoculation was done 24-hr after the first fungicide application using an ULVA+ sprayer on 3 Apr. Severity of downy mildewwas determined on 3, 13, 21, 29 Apr and 6 May, and expressed as the percentage of foliage area affected. Temperature averaged 77°F daily with a low of 68°F and a high of 85°F, and relative humidity averaged 79% throughout the trial. Measured variables were submitted to analysis of variance (ANOVA) using SAS v 9.4, and means were separated using Student Newman Keuls test.