Effects of pesticide application on the cold hardiness of Itea virginica L. 'Merlot'
Navazio, Mariya Merritt
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Pesticide applications can have a significant negative impact on the cold hardiness of nursery plants. Groups of 32 mature Itea virginica L., a woody perennial, were treated with the synthetic pesticides chlorfenapyr and soil-applied imadacloprid, the neem products, clarified hydrophobic extract of neem oil and azadirachtin, and a water control. The plants were then tested for cold hardiness once a month between October and February of 2004-2005. All of the treatments caused the plants to be significantly less cold hardy then those treated with the control. The plants treated with imadacloprid decreased the plants’ hardiness the least overall. The insecticide with the most impact on hardiness overall was the neem-based azadirachtin. The relative loss of cold hardiness between treatments was extremely variable over time, making the timing of cold injury in a particular location of importance in selecting a pesticide. Index words: Cold Hardiness, Biorational Pesticides, Itea virginica