MSU is an affirmative-action, 

equal-opportunity employer. 

College of

Agriculture and

Natural

Resources

Department of

Plant, Soil and

Microbial Sciences

1066 Bogue St.

A286 Plant and Soil

Science Bldg.

Michigan State University

East Lansing, MI

 48824-6254

517-355-0271

Ricardo Jones 

Chemical Review Manager 

Risk Management and Implementation Branch I (RMIB 1) 

Pesticide Re-evaluation Division (PRD) 

Office of Pesticide Programs 

US Environmental Protection Agency 

Dear Mr. Jones October 5, 2014 

This a letter to support maintenance of the current recommended 

application rates for Chipco Signature (fosetyl-Al), which currently is 

applied twice monthly, or at a rate of 17.6 lbs active ingredient (AI) per 

acre per month. My understanding is the EPA is looking to reduce the 

amount of fosetyl-Al. Since most turfgrass managers are well aware of 

the fact that other phosphite products, sold as fertilizers, can substitute 

for Chipco Signature, there would be an increase in the use of 

unregulated phosphite products if fosetyl-Al were rendered ineffective 

due to low application rates. Would it not be better for the EPA to have 

some control on the amount phosphite products used for disease control 

as is the case with Chipco Signature? 

I find it hard to understand the EPA recommendation for reduction in the 

use rate of Chipco Signature. The product is, in reality, a phosphite. It 

has low mammalian toxicity and low environmental impact. It is also 

primarily used on putting greens, which normally amounts to around 2 1⁄2 

acres of an entire golf course. 

Chipco Signature is one of the mainstays of many disease and plant 

health programs on golf putting greens. Whereas the fosetyl-Al has a 

direct effect in controlling Pythium blight, caused by Pythium 

aphanidermatum, it has also been shown to provide the plant with 

induced systemic resistance (ISR). This allows for other fungicides to be 

used at lower rates or extended application intervals thus reducing the 

environmental impact of more toxic fungicides. Chipco Signature also 

contains a green pigment that reduces the stress on the turfgrass plant. 

By reducing the stress on the plant, it makes the turfgrass plant healthier 

and less likely to be susceptible to minor diseases. This can also reduce 

the fungicide load put into the environment. 

Fungicide resistance is becoming huge problem on golf courses for 

important diseases like dollar spot, caused by Sclerotinia homoeocarpa, 

and crown rot anthracnose, caused by Colletotrichum cereale. S. 

homoeocarpa has become resistant to the benzimidazole, dicarboximide 

and DMI chemistries of fungicides while C. cereale has become resistant 

to the benzimidazole, QoI and DMI classes. Of these chemistries, only 
the DMI chemistries can still be used for these diseases because the 

resistance expressed to the DMIs is a shortening of the interval of 

control. This requires the DMI fungicides to be applied more frequently 

and, often times at higher rates, to achieve adequate control. There is 

also resistance to mefenoxam by the Pythium blight pathogen, Pythium 

aphandermatium, which Chipco Signature effectively controls at current 

application rates. There has never been any reported resistance by any 

turfgrass pathogen to Chipco Signature. It is important for golf course 

superintendents to have fungicides like Chipco Signature where 

resistance is not a problem. 

For the sake of the turfgrass industry, I would like to ask you to 

reconsider your potential recommendation and allow Chipco Signature to 

be applied at its current application rate of 17.6 lbs. AI per acre. 

Sincerely yours, 

J M Vargas Jr. Ph. D 

Professor 

Dept. of Crop, Soil, and Microbial Sciences 

Michigan State University