Microsoft word - 051212 managing the control of rhizoctonia root rot -may 2012

Managing The Control of Rhizoctonia Root Rot: Quadris Timing and Mixing  
Rhizoctonia root rot has reared its ugly head as being one of the more devastating production problems that the sugar beet industry has had to address on an annual basis. Rhizoctonia solani survives in the soil for many years. Rhizoctonia solani attacks seeds of plants below the soil surface, but can also infect roots, leaves and stems. . An infected seedling can survive early season damping off and yet will express deterioration symptoms later in the plants life. This is why we will observe distinct symptoms of sugar beet plants infected by Rhizoctonia solani during the root development stage as is shown in the picture below. The devastating effect observed below and the impact on sugar beet storage is why the control or suppression of rhizoctonia root rot is so important. There are various environmental conditions that put the plant at higher risk of infection due to Rhizoctonia; the pathogen prefers warmer wet climates for infection and growth. The fungus has a wide host range. Strains of Rhizoctonia solani may differ in: the hosts they are able to attack, the virulence of attack, selectivity for a given host ranging from nonpathogenic to highly virulent, the temperature at which the attack will occur, the ability to develop in lower soil levels, the growth rate, and the survival in a certain areas. These factors may or may not show up given the environment and host that Rhizoctonia attacks.  The cropping rotation of the Southern Minnesota Beet Sugar Cooperative growing area does not allow for a break
in the pathogen cycle for Rhizoctonia solani. Corn, soybeans and sugarbeets are all host to Rhizoctonia solani
and specifically the AG 2-2 IIB strain which is most common in the SMBSC growing area. The data presented in
Table 1 shows the influence of fungicides applied in the presence of Rhizoctonia solani strain AG2-2 IIB. Refer
to the SMBSC annual research report for more information on the efficacy of fungicides for control of
Rhizoctonia root rot
Southern Minnesota Beet Sugar Cooperative – May 10, 2012 Table 1. Rhizoctonia Control as Influenced by Fungicide and Variety
Buf alo Lake, 2011

Ext. Suc.Per Revenue
Product *
Application criteria
Variety type
Acre (Lbs.) % of Mean
* Proline + (NIS) + Supertin + Gem w ere applied sequentialy in all treatment for cercospora leaf spot control The following points are responses to recent questions we have received in reference to managing Rhizoctonia root rot in sugarbeets with Quadris and the mixing with other products. Growers should realize that Quadris is not the only product available for control or suppression of Rhizoctonia root rot as shown in table 1. However the following points will concentrate on Quadris fungicide since this product has been the basis for most of the questions addressed to the SMBSC Agricultural staff. Southern Minnesota Beet Sugar Cooperative – May 10, 2012 Notes: Quadris applied alone and with other products for control of Rhizoctonia root rot in 2012.
1. Quadris should be applied at the recommended rate of 14.3 oz. per acre in a 7 inch band. The maximum labeled rate of
Quadris is 15.5 oz. per acre regardless of whether the application is made in a band or broadcast. Remember that a broadcast
application is the equivalent of a 1/3 application rate relative to the recommended 7 inch band application rate.
2. Band vs. broadcast Quadris: Many fungicides when applied for root diseases are labeled for use rates based on ounces per 1000 ft. of row in a specific band width. Quadris labeled rate for Rhizoctonia root rot control is based on a 7 inch band per 1000 ft. of row. For this reason the broadcast rate and the band rate are the same rate per acre. Applying Quadris to a wider application such as 11 inch or broadcast does not change the application rate of Quadris. 3. Application in a 7 inch band should be made in a mix of Quadris and water at an equivalent of 20-25 gallons per acre broadcast 4. The agitation in the spray tank should be kept at a medium to low level to avoid precipitation. 5. Products can be mixed with Quadris with some reservations a. Insecticides can be mixed with Quadris, however avoid using products with high loads of emulsifiable concentrate. Lorsban Advanced and Mustang Max insecticides have reduced levels of emulsifiable. Asana insecticide has a higher load of emulsifiable concentrate and is a cotton seed oil based EC. Asana and Mustang Max have been used in the Michigan Sugar area in mixtures with Quadris. We spoke with Syngenta reps. and all three products should be o.k. to use with Quadris. Typical precautions to reduce potential injury should be observed, such as applications later in the day. b. Mixing sequence should be that Quadris should be added first and alloed to go in to solution and then add other products. c. Glyphosate products can be mixed with Quadris; however do not add an NIS or any oil based adjuvant. You can and should add an ammonium product to enhance the glyphosate product efficacy. You should realize by not adding the NIS or oil based adjuvant the efficacy of the glyphosate product may be reduced. d. You can add a grass herbicide, however you should not use a product with an emulsifiable concentrate or surfactant added (example: Select Max contains a surfactant and Select does not, so use Select). e. You should not add Outlook or Dual Magnum to the Quadris spray mix. Note that you can apply a two-way mix of Outlook
or Dual Magnum with glyphosate products.
6. Application of Quadris or any other fungicide for control of Rhizoctonia solani should be made prior to when the soil temperature reaches 65o F at the 4 inch depth. You can view the soil temperatures from the SMBSC weather stations on the SMBSC website.  The soil temperatures can be accessed on the SMBSC website at   Look under the Agronomy tab for a link to the Soil Temperature Graph.  Click on this link and you will be taken to the graph.    7. SMBSC is recommending that you make the application of a fungicide for control of Rhizoctonia root rot as soon as you
are able to get into the fields and no later than the middle of next week (approximately May 18th). You need to remember
that the fungicides need to be applied prior to the Rhizoctonia spore germination. Since the growth of the Rhizoctonia Solani
occurs at approximately 65o F you should apply the fungicide when the soil temperatures reach approximately 62o F. Soil
temperatures are currently in the upper 50 degree area and have peaked above 60 degrees. The forecast for early next week is for
highs in the lower 70’s which should drive the soil temperatures to peak close to or above 65o F.
8. Rhizoctonia is a difficult disease to control and no single treatment can be expected to provide 
adequate control when used alone.  Be sure to utilize a program approach using several control 
options to effectively manage this disease.

Southern Minnesota Beet Sugar Cooperative – May 10, 2012


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