Lorsban/Pilot (Chlorpyrifos) is Back for Pennsylvania Tree Fruit in 2025

We thought the insecticide chlorpyrifos (trade name Lorsban, Pilot, Warhawk, and others) first registered in 1965 was effectively killed for use in US agriculture when, in August 2021, the US-EPA issued a 'final rule' prohibiting the use of the organophosphate insecticide chlorpyrifos on all food or animal feed crops after February 28, 2022. This ruling was challenged by a registrant of the insecticide and various grower groups, and a review by the U.S. Court of Appeals for the 8th Circuit found that EPA was 'arbitrary and capricious' in this action because it did not allow for a public comment period or for an interagency review with the US Department of Agriculture.

The USDA Office of Pest Management Policy (OPMP) scientists believed, based on EPA's own documents, that EPA could retain certain uses of chlorpyrifos that met EPA's safety standards on 11 different crops, including apple, cherry, and peach, that were worth $59 billion in annual sales. On November 2, 2023, the ban on chlorpyrifos was revoked by the 8th Circuit Court of Appeals, which found the ban placed a severe economic strain on American growers and distributors and that EPA had not followed proper procedures when it banned all food uses of chlorpyrifos. A new Federal Register Notice from the EPA reinstating the food tolerances for chlorpyrifos is forthcoming very soon. But as of December 28, 2023, all previously existing food tolerances have been legally reinstated by Court mandate.

The bottom line for US agriculture is that all uses on all agricultural crops, such as fruits and vegetables, can be used according to the prior labels in 2025 for products that remain registered. The exceptions are the states of California, Hawaii, Maryland, New York, and Oregon, which have all banned chlorpyrifos use on food crops grown sold in their state jurisdictions, and those bans will remain in effect unless they change them at the state level. Additional restrictions on chlorpyrifos use are in place for some large buyers, such as Whole Foods, meaning that packers such as Rice Fruit Company will not be able to accept fruit treated with Lorsban.

Two years since the 'final ban' on chlorpyrifos, numerous manufacturers, including Corteva, have stopped producing various chlorpyrifos products. Only Gharda Chemicals (with a local office in Newtown, PA and based in India) and Drexel are still producing chlorpyrifos products, such as Pilot 4E, Pilot 15G, Chlorpyrifos 4E, Chlorpyrifos 15G, etc. which will be sold locally through Helena and Nutrien, but with possibly limited stocks for this season. Companies that have already submitted voluntary cancellation requests to the EPA cannot undo those requests, so it is doubtful that Corteva or any others would gear up for chlorpyrifos production again in the future.

It should not be overlooked that this 2025 season will also be a good year for growers to use up existing stocks of chlorpyrifos products for other uses, such as cherries, grapes, vegetables, etc., which will not remain legal beyond the 2025 season. Just follow the label restrictions on those products before using them.

Future of Chlorpyrifos

The USDA Office of Pest Management Policy (OPMP), in public comments to the EPA, recommended continuing the safe use of chlorpyrifos by US-EPA standards for the following crops: alfalfa, apple, asparagus, tart cherry, citrus, cotton, peach, soybean, strawberry, sugar beet, spring wheat, and winter wheat. These uses come with additional regional restrictions, meaning not all uses are national. For example, use on cherries going forward would only be for Michigan and only for tart cherries, not sweet cherries. And even when future use of chlorpyrifos becomes limited to this small list of crops, the EPA will still continue registration review and may decide to impose additional restrictions based on risks to applicators, ecological exposure to endangered species, etc. Therefore, the longer-term outlook beyond 2025 remains uncertain for chlorpyrifos (as well as for other OP chemicals like diazinon, phosmet, etc.). Keep in mind that the ultimate registration review deadline for EPA's entire pesticide portfolio is now set for 2026. If the remaining chlorpyrifos uses can be shown to be safe, it is possible that uses will remain legal for a longer time, but all of this is uncertain as of now.

Safety

Chlorpyrifos labels have already been heavily restricted to reduce or eliminate the ingestion of residues on fruit and worker exposure. In apple, only early-season dormant sprays well before bloom and fruit development are allowed to prevent consumer ingestion (especially children) of harvested fruit. The current Pilot label allows for its use on the apple, cherry, and peach trunks mid-season for moth and beetle borers if the foliage and fruit are not contacted during the application. From personal experience, I believe such sprays in the middle of the season will contact the fruit and should not be used. Worker exposure safety has been addressed by stricter personal protective equipment (PPE) requirements requiring applicators to wear protective Tyvek suits and respirators in a tractor cab with additional filters.

Pests Controlled by Chlorpyrifos by the Allowed Dormant Spray in Tree Fruit

Borer Pests: The most critical use of this insecticide in tree fruit is for moth and beetle borer pest control. The very early season dormant chlorpyrifos application at the highest 2 lb. active ingredient on apple, peach, plum, and cherry has been shown to control these important pests five months after application, midseason (mid-August). I would only recommend spring dormant sprays rather than the post-harvest applications in October/ November, as the residues from that application would have to last up to another five months before contacting borer eggs and larvae the next season. Although this early spring dormant spray can be applied by airblast sprayer at dormant for San Jose scale and other foliar/fruit pests, borer control will be much better with a targeted high-volume handgun application to the trunk to thoroughly cover the trunk and kill both eggs and larvae mid-season. Dormant sprays by handgun or airblast on grape are allowed as well for the grape root borer, but chlorpyrifos at this time will also effectively control the overwintering eggs of the invasive spotted lanternfly (SLF). This ovicidal activity by chlorpyrifos for lanternfly eggs was only found after the cancellation, so it does not have SLF currently on the Pilot or any other formulations, but we will work with the registrant and the Pennsylvania Department of Agriculture to obtain a 2(ee) label amendment to add this pest.

San Jose Scale Control and Residual Control of Other Pests: airblast applications at dormant with high water volume and complete applications will give excellent San Jose Scale (SJS) control at the full label rate, but some farms are suspected of having resistance to this product. Rosy apple aphid (RAA) is another pest that appears almost completely resistant to chlorpyrifos and pyrethroids. Complete coverage is critical for SJS control of the immobile scale at this time and will aid in killing the mobile SJS 'crawler' later in the season with its residues (see table). SJS has generally increased in most commercial orchards since the chlorpyrifos cancellation, as has plum curculio and tarnished plant bug, possibly for the same reason.

Control with Chlorpyrifos Alternatives

• Lesser peach tree and Peach tree borers – pheromone mating disruption (MD), not best for smaller orchards. Thiodan was also effective for borer trunk sprays but was canceled at least ten years ago.
• American plum borer – two generations/season and no MD commercially available.
• Dogwood borer – MD effective and available, problems with mating outside of alternate hosts (oak galls) and on small scale.
• San Jose scale – Centaur, Esteem, Movento.