Dealing with 'least toxic pesticides'
Recommendations and decisions to use “least toxic pesticides” and “pesticides as a last resort” have flourished in the last decade, but according to three scientific organizations – the Weed Science Society of America (WSSA), the American Phytopathological Society (APS) and the Plant-Insect Ecosystems Section of the Entomological Society of America (P-IE ESA) – these are not the correct approaches to the pesticide component of an Integrated Pest Management program.
The three organizations have joined to take an objective look at the problems associated with “least toxic pesticides” applied as a “last resort” and today issued the following statement:
IPM is Fundamental Wherever Pests Must Be Controlled
It is essential to practice IPM, whether managing weeds, insect pests or plant diseases – on the farm, on commercial sites, on public lands, or in or around the home. Key components of IPM include making the habitat unfavorable for pests, excluding pests where feasible, using proper sanitation practices, monitoring the infestation level, knowing the pest tolerance level for the specific situation and implementing the necessary management practices.
Judicious use of pesticides is a critical component of many IPM programs. Judicious (careful) use refers to various practices – following all label directions and making all appropriate stewardship decisions required in the particular situation. This includes applying a product registered for the target pest(s) after accurate pest identification, and consideration of the level of infestation and the potential for economic, health or other negative pest impacts. Careful use extends beyond pesticides to household chemicals, automobiles, medicines, alcoholic beverages, and countless other products that are part of our daily lives.
The Problem with Selecting Only “Least Toxic Pesticides”
- “Least toxic” implies there are pesticides available for every pest spectrum that are least toxic to everything else. This is not true. The toxicity of a pesticide depends on what is being evaluated – short-term or long-term toxicity – and who or what may be affected (e.g. applicators, farmworkers, livestock, wildlife, pets, birds, fish, beneficial insects, earthworms, sediment-dwelling organisms, crops). It is also important to remember that toxicity is not the same as risk, which is dependent on both toxicity and exposure.
- The risk associated with the use of pesticides and other chemicals is managed by establishing safe exposure levels based on the toxicity specific to each product. Assigning a “most” or “least” toxic rating does not equate to actual risk when the product is properly applied. For example, the label of a pesticide product that may cause skin irritation will also contain requirements for personal protective equipment that safeguards the skin, while a product that may affect fish will contain use directions, precautions and possibly even restrictions intended to protect fish. This is why the EPA-approved label instructions must be followed.
- All pesticides – including those referred to as “least toxic,” “organic” and “natural” – are toxic to one or more pests and possibly humans and other organisms as well. Use of these terms can lead to false security regarding the need for careful handling of pesticides and proper environmental stewardship.
- Over-reliance on a “least toxic” pesticide can cause new problems. For example, glyphosate is considered a “least toxic” herbicide choice, but overreliance on it has led to significant weed resistance problems. Over-use or misuse of any pest management tactic can cause problems – for example, cultivation to control weeds on hilly land can cause soil erosion, and excessive hand-hoeing can cause back injuries and increase the risk of skin cancer.
- Often, “least toxic” products do not work as well on the pest(s), leading to the need for re-treatment with another pesticide on larger and/or harder-to-control pest infestations. This can result in higher costs, reduced control and undesirable environmental effects attributable to the pest.