Topsin M Section 18 request for blueberries denied by EPA
After seven years of granting emergency exemptions for the use of the fungicide Topsin M (thiophanate methyl) as a replacement for Benlate (benomyl) in blueberries in Michigan, the Environmental Protection Agency (EPA) has not granted our emergency exemption request for the 2008 season. Of the Topsin M Section 18s originally issued to multiple states for blueberries, the only remaining applicant in 2007 and 2008 was Michigan, indicating that growers in other states had found alternatives among the currently registered products.
The reason for the denial of the Topsin M Section 18 request this year was the need for a strong emergency rationale and avoided loss picture in light of the registration of a number of new fungicides directly labeled for the diseases of concern. This made it very hard to argue that this year’s request could meet even the minimum requirements for significant economic loss (i.e., 20 percent yield or gross revenue loss, or 50 percent net operating revenue loss). The EPA did listen to our concerns for maintaining a resistance management program for the future, but to reasonably narrow the emergency exemption program to "urgent and non-routine" situations, the Section 18 program is geared only to cases of demonstrated fungicide resistance that result in significant economic losses. In addition, new data regarding the toxicological status of Topsin M did not favor this product in its review by the EPA. It is my understanding that if and when an emergency situation does develop, the EPA will reconsider our request.
Since we cannot use Topsin M this year, and its fate regarding full registration for blueberries is unclear, we need to consider alternative fungicide options. Michigan blueberry growers have done very well in rotating different fungicide chemistries, which is important for fungicide resistance management. Topsin M has a different chemistry from all other fungicides in our arsenal. Therefore, we have to be careful to not overuse the remaining fungicides since both the strobilurins and sterol inhibitors are at risk of resistance development in target fungi.
Good alternatives for control of Phomopsis and mummy berry are Pristine (pyraclostrobin + boscalid), Indar (fenbuconazole) and Orbit (propiconazole), whereas Bravo (chlorothalonil), Ziram (ziram), and Captan (captan) have moderate efficacy as protectants. It is important to remember that Indar and Orbit belong to the same chemical class (sterol inhibitors) and have a 30-day PHI. Serenade (Bacillus subtilis) is also an option for mummy berry control. Alternatives for control of anthracnose fruit rot are Abound (azoxystrobin), Cabrio (pyraclostrobin), Pristine, Switch (cyprodinil and fludioxonil), Bravo, Captan, Captevate (captan + fenhexamid), and Ziram. Botrytis blossom blight is controlled well by Captevate, Elevate (fenhexamid), Switch, and Pristine. Table 1 lists various fungicides and their efficacy against blueberry diseases.
Table 1. Effectiveness of fungicides for blueberry disease control.
|Fungicide||Mummy berry||Phomopsis twig blight and canker||Fusicoc-um canker||Alter-naria
|Botrytis blight and fruit rot||Phytoph-thora|
|Abound||+ / ++||+ / ++||++||?||++||++++||+||?|
|Topsin M + Captan or||++||++||+++||+++||+||+++||+++||0|
|Ziram||+ / ++||+ / ++||++++||?||++||+++||+++||0|
|Cabrio||+ / ++||+ / ++||+++||?||++||++++||+||?|
|Captan||+||+ / ++||++||+||+||++ / +++||+||0|
|Lime sulfur||++ / +++||+||++*||?||?||+ / ++||+||0|
|Serenade||++ / +++||++ / +++||+ / ++||?||?||0||?||?|
|Switch||+||++||+ / ++||?||++++||+++||++++||?|
|Ziram (3 Ib)||++||+||++||++||+*||++||+||0|
|Ziram (4 Ib)||++||++||+++||++ / +++||++*||+++||++||0|
0 = not effective, + = poor, ++= fair, +++ = good, ++++ = excellent, ? = not known. Ratings are based on published information and observations in Michigan and other states.