C.O.R.N. Newsletter: 2014-07

At the regional soybean disease workers meeting in Florida earlier this month, colleagues from Kentucky and Indiana both reported the presence of the fungus,Cercospora sojina, that are resistant to the strobilurin fungicides.  This fungus causes frogeye leaf spot on soybean.  There are lots of Cercospora species that cause disease on a number of different hosts (gray leaf spot on corn; Cercospora on beets etc.) To date we have not identified any Cercospore sojina isolates that are insensitive to these fungicides.  More monitoring will take place in 2014. 

Also at that meeting – there was quite a bit of discussion about kudzu.  Much of it was killed back, but unfortunately it had been dry in some parts of the south, so the rust spores had survived in some areas.  Predictions on soybean rust for 2015 will depend on how long it will take for the kudzu to leaf out – which will be delayed this year; and then how long it will take rust to begin to develop on the kudzu.  Lots of discussion and as always lots of interest.

Two new videos are out on soybean rust.  The videos include highlights from numerous research and Extension projects carried out by land-grant university researchers from around the country involved in soybean rust research and monitoring efforts.  They were produced with support from the American Public Land Grant Universities Association, Cooperative Extension, the Experiment Station Committee on Organization and Policy (ESCOP), the U. S. Department of Agriculture’s National Institute of Food and Agriculture, and the United Soybean Board.

The first video (http://youtu.be/m07iu6HaQpc) provides an overview of soybean rust, its impacts, its spread in the U.S., and how responding to this disease has changed the way researchers, Extension educators and farmers now approach soybean diseases in general.

The second video (http://youtu.be/8NQW7YAmEBE) deals with efforts undertaken across the country to model, predict and forecast soybean rust through the use of “sentinel plots.”

Among its many accomplishments, the team has identified management strategies for soybean rust; made efforts to test and register fungicides for use in the U.S., giving soybean producers more options for controlling the disease; and established an extensive network initially of over 2,300 sentinel plots, helping farmers know more precisely where the disease is likely to occur and when and what types of fungicides to use.

A new fungicide which has activity towards Oomycetes was labeled this month.  INTEGO Solo is the name of the product from Valent, but much of the initial field testing was done in Ohio.  The active ingredient ethaboxam, provides similar or greater efficacy towards the diversity of watermolds that attacks soybean and corn seed and seedlings in Ohio.  This will give an added benefit to many of the areas in the state that continue to struggle with replanting issues.

Pelletized lime has been on the market for over ten years in Ohio. It consists of finely ground limestone held together by some form of binding agent to make a pellet. Since it requires more processing than traditional ag lime it often costs considerably more than bulk ag lime. However, since it is in a pellet form it can easily be blended with other fertilizers and applied with regular dry fertilizer equipment.  

University research has shown that pelletized lime does not raise soil pH faster than high quality ag lime. This should not be a surprise since high quality ag lime includes a large portion of material this has been finely ground.  

Pelletized lime is one of the many sources of lime available to producers in Ohio. When evaluating a pelletized-lime source ask for the analysis sheet to obtain the Effective Neutralizing Power (ENP) value. Ohio lime regulations require liming materials sold in Ohio to have the ENP listed on the analysis sheet. This value should be given as pounds of ENP. The ENP for pelletized lime would be determined on the lime source prior to the pelletizing process.  

Effective neutralizing power takes into account all the components that determine the quality of the lime, i.e., neutralizing ability, particle or grind size, and water content. This value will allow a producer to determine the actual price per pound of neutralizing ability for a lime source and also to calculate how much of a source will be needed to equal a ton of recommended lime. For example, if the lime recommendation was for two tons (one ton = 2000 pounds), a lime source with an ENP of 1000 pounds would require an application of four tons to satisfy the two ton lime requirement since for every ton of this lime source it only provides an effective neutralizing ability of 1000 pounds. If the lime source had an ENP of 1500 pounds, it would require an application of 2.7 tons to fulfill the requirement of two ton recommendation of lime. These calculations would also be true for pelletized lime source.  

Once a producer knows how much lime needs to be applied for a source they can compare price based on ENP. In other words, a producer can determine how much effective neutralizing material they are actually buying in a source. Also remember if adding lime this spring, consider the following management practices: 

1)      2 ton applications may be made anytime during the cropping season

2)      Applications > 2 tons should be split applied

3)      Do not apply more than 8 tons in one season

4)      Urea forms of N fertilizer should not be surface applied where lime has recently been surface applied to prevent volatilization losses. 

In summary pelletized lime is one of many sources available to Ohio producers. Its ENP value will allow comparisons to other lime sources. Additional information on lime may be found in Soil Acidity and Liming for Agronomic Production Bulletin AGF 505, (https://agcrops.osu.edu/specialists/fertility/fertility-fact-sheets-and-bulletins/AGF505.pdf)  the Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa (http://ohioline.osu.edu/e2567/). Possible effects of lime on spring applied herbicide performance can be found at (http://corn.osu.edu/newsletters/2010/2010-02).