EPA announces phase out of Guthion on almonds by 2007

By Marni Katz

Special to "California Almonds"

U.S. EPA announced June 9 a proposal to phase out all uses of azinphos-methyl (AZM), an OP insecticide known by its trade name Guthion, which has been under regulatory scrutiny for several years. Use on almonds, Brussels sprouts, pistachios, walnuts, and nursery stock is to be phased out in 2007 and other remaining uses are to be phased out in 2010. During the phase out, EPA is proposing additional restrictions, including reduced annual application rates, additional worker monitoring, and larger buffer zones to help minimize ecological risks.

Guthion is highly valued by almond growers for control of Navel Orangeworm (NOW), one of the most serious pests in almonds. NOW causes direct damage to the mature nuts. Damaged nuts are locations where the mold, Aspergillus, can gain a foothold and produce aflatoxins. 

“Part of what made Guthion good was the long residual activity which provided extended protection against the protracted third or fourth flights of NOW shortly before harvest.” said Gabriele Ludwig, Almond Board of California’s Senior Manager, Global Technical & Regulatory Affairs. “This was critical to provide protection for the different varieties of almonds as they are harvested at different times and it is not possible to get in to spray once harvest starts.”

Guthion, a popular choice among almond growers for control of navel orangeworm, is scheduled to be phased out by 2007, according to a June announcement from U.S. EPA (Photo by UC Statewide IPM Project)

Guthion went through re-registration at EPA in the late 1990's. At the time EPA found serious worker exposure concerns, though partly because they could not use data from intentional human dosing studies. The long residual was a problem from a worker safety standpoint, especially if workers needed to come in contact with the foliage. EPA had no data for dust from nut harvesting so assumed it was similar to hand harvesting. EPA made a difficult decision at the time to maintain some uses based on the economic benefits (or lack of alternatives) available then. In 1999 some Guthion uses were phased out, with other uses to be phased out in 2005. Additional uses, including tree nuts, were to be reviewed in 2005. They also required that the registrant provide more data on actual worker exposures.

In response to the worker exposure concern, however, EPA extended the re-entry interval (REI) from 14 days to 30 day for almonds.  New labels with the extended REI finally reached the market in 2004, and instantly reduced the number of almond acres treated with Guthion. Guthion use plummeted from some 50,000 acres treated in 2003 to some 4,000 acres in 2004, a drop from about 10% of the almond acreage to 1%.

“The impact of the 30-day REI was immediate - with growers choosing not to deal with the onerous personal protection equipment requirements for early re-entry, even if just to irrigate.” noted Ludwig.

In 2004 the United Farm Workers and others sued EPA over their decision to continue to allow the uses of Guthion and Imidan despite the worker exposure concerns. In January 2006, EPA signed a settlement agreement that they would review the worker safety issues by August 3, 2006.  Guthion’s worker exposure risk assessment has also been affected by controversy over the ethics of studies where humans are intentionally dosed with pesticides. If human studies data is used, then the worker risk concerns for Guthion are largely removed.

 During the 2005 review, EPA also focused more on the environmental effects with concerns for aquatic species being the risk driver, along with concerns for birds and small mammals.  Essentially, any use of Guthion posed a risk to non-target species based on the EPA ecological risk assessments.

Between the lawsuit, the ecological risk, the decision not to use human studies for Guthion, and the sense that a number of lower risk alternatives were available to most users of Guthion, the agency proposed to eliminate all remaining uses of Guthion by 2010, and uses for nut crops in 2007. As a result, an important option for integrated pest management programs in almonds will no longer be available.

“While almonds do have several alternatives available, none are the equivalent to Guthion.” explained Ludwig. Knocking down mummy nuts to remove over wintering sites for NOW is an important control tool. However, in some years, and especially in the southern San Joaquin Valley, there may not be enough moisture to break down the nuts before spring.

One of the main alternatives is Imidan (phosmet), which EPA reassessed in parallel with Guthion. EPA has not changed the REI for nut crops, but has proposed to extend the REIs for other crops.   The main other alternative is Intrepid (methoxyfenozide) which is lower risk. Both Imidan and Intrepid are not as effective as Guthion, especially under high pest pressure. Other alternatives include Lorsban (chlorpyrifos) and Pounce (Permethrin) “which both provide short term knock down, but have environmental issues of their own, or worsen other pest problems.” noted Ludwig. 

EPA is inviting public comments by Aug 8, 2006 before issuing a final decision. The ABC plans to provide comment. The Federal Register notice is available on EPA's Web site at http://www.epa.gov/fedrgstr/EPA-PEST/2006/June/Day-09/p8929.htm.

Comments may be submitted electronically at http://www.regulations.gov