by Julianna Wilson

What does the Dec. 28, 2023, court ruling mean for Michigan tree fruit growers who would still like to use chlorpyrifos against labeled insect pests on bearing trees?

In February 2022, the U.S. Environmental Protection Agency revoked all food tolerances for use of the organophosphate insecticide chlorpyrifos in response to a lawsuit advocating for banning its use.

This was despite already identifying 11 uses that could be exempt from this ruling based on risk data they had examined. A second lawsuit against EPA protesting this result caused this revocation to be vacated on Dec. 28.

So, what does this mean?

For Michigan tree fruit growers who have relied on formulations of chlorpyrifos (e.g., Lorsban, Govern, Warhawk) as a dormant spray against sap-sucking insects or a post-bloom trunk spray against borers, it means that for now, all previous tolerances are back for at least the 2024 field season.

In other words, if you still have chlorpyrifos in your spray shed, you can use it according to the label during the 2024 field season in bearing trees. That said, this doesn’t change whatever specific rules your processor, buyer or export market might have in place around use of chlorpyrifos and maximum residue limits.

If you don’t have any chlorpyrifos in your spray shed, you may find it more difficult to obtain because all but a handful of companies have voluntarily given up their product registrations. It is important to note that if a product is no longer registered, it can no longer be distributed or sold, but while tolerances remain in tree fruit crops, formerly registered formulations — such as Lorsban — can still be used.

That said, it is expected that as early as fall 2024, EPA will complete the process of revoking tolerances of chlorpyrifos for all but those 11 food uses. Among these 11 uses, in Michigan at least, chlorpyrifos tolerances are expected to remain for apples, peaches and tart cherries, but not sweet cherries.

So, while it is possible to use chlorpyrifos in these crops for now, it will be important for growers to be thinking about alternatives to its use and possible pest flare-ups, if they haven’t already.

In the spring 2023 issue of the Fruit Quarterly, Volume 31, Number 1, an article titled “Life After Lorsban” described best practices for managing borers and soft-bodied insect pests in orchards without chlorpyrifos.

These include:

Specific products and their recommendations, which are based on years of efficacy trials run at Michigan State University or by colleagues at other research institutions, are listed in the latest Michigan Fruit Management Guide E-154 from Michigan State University Extension.

Wilson is an assistant professor in the Department of Entomology at Michigan State University.

Source: MSU