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Peanut and Corn Disease Update

kemerait peanuts

Peanuts

Area peanut growers are now beginning to consider protecting their crop with fungicide applications.  However there have been some reports of a shortage of Chlorothalonil (Bravo, Echo, Chloranil, and others) this season.  Here are some recent comments from UGA Extension Plant Pathologist Dr. Bob Kemerait on the current Peanut Disease control situation:

1. Current conditions (warm weather with developing afternoon thunderstorms) create favorable conditions for leaf spot diseases and white mold.

2.  As mentioned in my previous e-mail, it appears that chlorothalonil (Bravo, Echo, Chloranil, etc.) will be “short” in our supply chain this year and I am already getting many calls and questions about it.

3.  Here are our UGA strategies for dealing with the shortage of chlorothalonil in peanut production:

A.  Consider using a strong leaf spot fungicide like “Headline” (9 fl oz/a, 45 days after planting) to initiate an excellent leaf spot program and to replace potentially 2 applications of chlorothalonil (30 and 44 days after planting).

B. Reduce the rate of chlorothalonil used in a leaf spot applications by partnering with another fungicide.  Examples include mixing chlorothalonil (1 pt/A) with Tilt (propiconazole, 2 fl oz/A) or  Alto (cyproconazole, 5.5 fl oz/A) or Topsin-M (5 fl oz/A).

PEANUT Rx: Using “prescription” fungicide programs based upon risk assessment in the field may also be an excellent strategy to reduce use of fungicides in general.

Corn

 

Also Southern Corn Rust has been confirmed in the area for some time now and many growers have already made a fungicide application on their corn crop.  Here are some comments from Dr. Kemerait on the disease situation in this year’s corn crop:

1.  Rust is widespread (and early) this year and found in fields that have not yet reached the tassel stage. (See our current map at http://scr.ipmpipe.org/).

2.  Sporadic afternoon and evening thunderstorms are likely to further move rust spores and also provide the moisture important for infection.

3.  I believe that this is the most significant threat of southern rust in Georgia in the past 10 years.

4.  Southern corn rust (SCR) reduces the photosynthetic capacity of infected leaves. More importantly, a field where SCR is not controlled may develop extensive lodging problems as the stalk is cannibalized for nutrients to feed the ear.

5.  Dr. Dewey Lee and I agree that protecting a crop from rust though the dough stage is beneficial.

6.  I recommend that growers spray by tassel growth stage and then again 2-3 weeks later, depending on the product used in the first application.

7.  On corn where rust is a severe problem, we have seen fungicides protect 25+ bu/A.