The Price of Oversight: Avoiding Phytotoxicity in Greenhouse Crops
Greenhouse growers face constant challenges in pest management, but one of the most preventable issues is phytotoxicity caused by improper pesticide use. A notable example involves seed geraniums sprayed with the active ingredient Spirotetramat, demonstrating the critical importance of carefully reading and following pesticide labels. The insecticide label specifically warns against use on geraniums and other sensitive species, yet accidental foliar spray application resulted in significant plant stress, including distorted and chlorotic (yellow) to bleached (white) leaves.
Phytotoxicity can manifest in various ways, such as necrotic (dead) flecks, leaf edge burn, discoloration, distorted growth, leaf or flower drop, and stunting or death of growing points. Injury can also occur from indirect exposure, such as runoff or leaching from treated hanging baskets onto sensitive crops below. It's worth noting that if the injury is not severe, plants may eventually grow out of it, though marketability will depend on the severity and timing of the application.
To avoid such incidents, it's essential to always read the label thoroughly before application, checking for specific warnings about plant sensitivity and environmental factors that might increase the risk of phytotoxicity. For instance, Spirotetramat is not recommended for use on several plants besides geraniums, including orchids, hoya, Dracaena, Cordyline, Schefflera, neanthebella palm, and ferns.
Additionally, calibrating equipment to ensure proper dosage, testing new products on a small scale, and keeping detailed records of all applications are crucial practices. Before using any new product, growers should test it on a small number of plants for phytotoxicity prior to widespread use.
By adhering to these guidelines and respecting the warnings on pesticide labels, growers can prevent costly mistakes and maintain the health and quality of their crops. This incident serves as a reminder that the label is not just a guideline – it's the law and your best resource for safe and effective pest management.
W. Garrett Owen
Assistant Professor of Sustainable Greenhouse and Nursery Systems, The Ohio State UniversityW. Garrett Owen is an Assistant Professor of Sustainable Greenhouse and Nursery Systems in the Department of Horticulture and Crop Science at The Ohio State University. He has an appointment in research, teaching and Extension. His area of expertise is plant nutrition; plant growth regulation; and production problem diagnostics.
