Phytotoxicity from the insecticide Spirotetramat on geraniums. Photo: Thomas G. Ford
While the label is considered to be “the law” we often see growers try to stretch the pesticide label to meet pest control challenges that they are facing in their greenhouse, field, or orchard. While in many cases this practice on non-food crops is often ignored by regulators and the industry, it can lead to significant crop damage when the label is totally disregarded.
Recently, I visited with a grower that had utilized the OHP Insecticide/Miticide, Kontos. Kontos is an excellent systemic insecticide that is both xylem and phloem mobile. The grower decided to use their 1:100 fertilizer injector to apply the product to the various floriculture crops that they were growing in their greenhouse operation. Utilizing the existing fertilizer injector to apply pesticides often seems like a great practice, but over 75% of the fertilizer injectors that I have tested for growers over the last eighteen years were not working properly and were either metering out too much product through the irrigation water or too little product. When too much product like an insecticide goes out through the irrigation system and is applied to a crop there are obvious concerns about phytotoxicity and plant injury. When too little product is applied through the system, a sub-lethal dose may be delivered to the target which results in poor efficacy and a greater potential for pest resistance to develop.
The Kontos label specifically warns growers that the product is not recommended for use on geraniums (Pelargonium spp.), orchids, hoya, Dracaena, Cordyline, Schefflera, neanthebella palm, and ferns. The label also states that only one application per season can be made to Hydrangea spp., Impatiens spp., crotons, Fuchsia hybrids, Petunia, Peperomia, stocks, or cyclamens. The grower in this case applied Kontos to all of their floriculture crops which led to a significant level of phytotoxicity in their geraniums. The probability of plant injury in this case was made more likely because of the use of an older uncalibrated injector, the inability of the grower to meter out a precise dosage based on container size, and a crop with known sensitivity issues to the compound.
While the lesson learned in this case may be a bitter pill to swallow, it reinforces the concept that we all must read, understand, and follow the pesticide label thoroughly. It also alerts us to the plant injury potential that can be observed when an improperly maintained piece of equipment is used in the field or greenhouse to apply pesticides.