02/03/2022
Imidacloprid Insecticide for home gardeners and plant enthusiasts.
I am a licensed pesticide applicator and certified arborist with a M.S. in biology and over 20 years’ experience in Commercial Nursery and Grounds Management. One of the focuses of my thesis research was the impact of imidacloprid on the reproductive success of plants which yielded some interesting data. I often find myself at odds with plant enthusiasts over the use of imidacloprid and other neonicotinoids. I was asked by someone in one of the plant groups to provide the reasoning behind my criticism of their practice. So, this is my professional opinion on the use of neonicotinoids.
What it is:
Imidacloprid is a synthetic formulation of ni****ne that acts as a pesticide by interfering with acetylcholine receptors in the central nervous system causing paralysis and death. It is sold under the trade name Merit®and is marketed for homeowners as Bayer Advanced Tree and Shrub®or 3in1®. It is no longer under patent and can be found in many other products and formulations as well.
How it works:
Imidacloprid and other neonicotinoid products can function as a contact insecticide, but more importantly, as a systemic product that is taken up and distributed throughout the entire plant. Insects that feed directly on plant tissues or fluids will uptake the chemical and become paralyzed. This chemical can be applied as a liquid foliar spray, a soil drench, trunk injection, or granular soil application to control a wide range of insects.
The Good:
These products work extremely well for controlling plant pests, are easy to apply, can be purchased without special licenses, and have long residuals that reduce the number of applications necessary. Application and mode of action allow for targeted application with minimal “off-target” dispersal. These pesticides are invaluable for controlling pests such as adelgid in large evergreens (Hemlock, Spruce, Fir, Pine).
The Bad:
Neonicotinoids are systemic products that are distributed throughout all parts of the plant. These are non-selective pesticides, which means that they will kill pretty much anything that contacts or consumes them including pollinator insects, larval foliar feeders, and even birds that consume fruit, pollen, or nectar. Even non-lethal exposure has been shown to alter the behavior of some organisms. Flowering plants attract insects and even trees that are “wind-pollinated” and don’t produce showy flowers are still heavily visited by insects for pollen. It lasts a LONG time. Some of these products (imidacloprid) can have an effective residual presence in evergreen trees, such as hemlock, for 5-10 years. Deciduous trees cycle faster, but the product is present from the time of treatment through leaf drop, at least. It doesn’t work for everything. Imidacloprid does not kill mites, they are not insects, and treatment is often followed by severe mite outbreaks. It also does not kill armored scale, which is very common on hemlock. Dinotefuran, another more expensive neonicotinoid, is effective on armored scale, but costs much more to purchase. Widespread use and misuse of these products in agriculture, home garden, and pest control have led to serious environmental impact concerns that have resulted in banning these products in several countries.
The point:
Pesticides are a necessary part of horticulture and agriculture but are also directly associated with declining insect populations, aquatic habitat degradation, and human health issues. We, as pest control professionals and plants people, have an obligation to use them responsibly and be aware of the impacts that they may have. Pest control should identify the pest and plant, select a treatment that will be most effective with the least collateral impact, and follow label guidelines explicitly. The label is the law, and failure to follow label guidelines is a violation of state and federal law (US), and environmentally irresponsible.
T.L.W.
