Effects of Insecticides on Gas Exchange, Vegetative and Floral Development, and Overall Quality of Gerbera
by James D. Spiers, Fred T. Davies, Jr., Chuanjiu He, Carlos E. Bogran, Kevin M. Heinz, Terri W. Starman, and Amanda Chau
This study evaluated the influence of insecticides on gas exchange, chlorophyll content, vegetative and floral development, and plant quality of gerbera (Gerbera jamesonii Bolus ‘Festival Salmon’). Insecticides from five chemical classes were applied weekly at 1x or 4x their respective recommended concentration. The insecticides used were abamectin (Avid), acephate (Orthene), bifenthrin (Talstar), clarified hydrophobic extract of neem oil (Triact), and spinosad (Conserve). Photosynthesis and stomatal conductance were reduced in plants treated with neem oil. Plants treated with neem oil flowered later—and at 4x the recommended label concentration had reduced growth, based on lower vegetative dry mass (DM) and total aboveground DM, reduced leaf area, thicker leaves (lower specific leaf area), higher chlorophyll content (basal leaves), and reduced flower production. Plants treated with acephate at 4x the recommended label concentration were of the lowest quality due to extensive phytotoxicity (leaf chlorosis). Plants treated with 1x or 4x abamectin or spinosad were of the highest quality due to no phytotoxicity and no thrips damage (thrips naturally migrated into the greenhouse). The control plants and plants treated with 1x bifenthrin had reduced quality because of the thrips feeding damage; however gas exchange was not negatively affected.