December 10, 2019

Why insecticides?

Every year, approximately 100 million acres of American farmland are treated with lethal insecticides, killing or harming an estimated 3.5 quadrillion insects—according to our new report.

It’s currently uncertain whether insects can feel pain at all. But the sheer number killed by insecticides—and the potentially excruciating nature of those deaths—means that making pesticides more humane has a good chance of preventing large amounts of wild animal suffering.

Pesticide reform also has the advantage of being relatively easy to implement responsibly.

One of the biggest challenges to most wild animal welfare interventions is figuring out the net effect on all the species in the community. This is especially true when population sizes change. For example, falling wolf numbers might lead to rising coyote numbers, leading to falling fox numbers, leading to rising mouse numbers, leading to rising tick numbers—or they might not.

If we can replace one insecticide with another that kills the same number of insects less painfully, we can reduce suffering without changing the total insect population. That significantly narrows the range of possible unintended consequences.

The goal of this report is to lay a foundation for future projects to improve wild insect welfare by promoting more humane insect pest management practices.

Key takeaways

1. The evidence supporting insect sentience is sufficient to argue that, in combination with the large number of insects, we should afford some consideration to insect welfare.

2. Agricultural pest insect management practices may be a particularly tractable avenue for improving the expected welfare of a large number of insects.

3. At this point, key unknowns make it difficult to recommend a particular insecticide or non-insecticidal pest control method as more humane. However, nerve and muscle agents (such as organophosphates and carbamates, or pyrethroids and pyrethrins) are faster-acting than insecticides with other modes of action (such as insect growth regulators, or Bt toxins).

4. Non-insecticidal methods of pest control may be gaining popularity and should be considered when developing more humane pest insect management practices. The net welfare impact of non-lethal methods is dependent on ecological factors and the specific organisms involved.

Next steps

In addition to the report itself, I developed two tools to facilitate further research.

The first is a database of insecticidal compounds, their modes of action, and their insecticidal mechanisms. This database is under development and may be expanded to include pests targeted, brand names, and chemical fact sheets where available.

I have also developed a rough impact estimate table outlining a method for using a pest control literature review to calculate the minimum number of insects affected by U.S. agricultural insecticide use.

As part of our upcoming strategic planning and inter-organization coordination process, Wild Animal Initiative will be evaluating the course of our future research on insect welfare. Currently, it looks like the most promising direction would be to fill in the gaps necessary to evaluate specific insecticide interventions:

• What are the economic injury levels (EILs) for particular crop-pest pairs?

• Can EILs be used to generate estimates of the number of insects affected by pest management?

• On which insect species and crops are particular insecticides or pest management methods used?

In the process of creating this report, many more questions arose than were answered. Despite this, the report provides an overview of the insect welfare landscape and the potential avenues for further intervention research.