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Agronomic Crops Network

Ohio State University Extension


Acceleron® Challenge – I lost

During the past dozen or so years, we have been recommending the highest rates of metalaxyl or mefenoxam for soybean seed that is planted in Ohio’s Phytophthora sojaecountry.  We have a lot of data collected during this time period to support this.  There are a couple of things in play here at the moment. 

1.       We have increasing number of fields in Ohio that have populations of another oomycete, Pythium spp. that are highly insensitive to metalaxyl/mefenoxam (more on this later) and;

2.       A growing number of new seed treatment compounds have recently entered the market  where other active ingredients also have efficacy for Phytophthora and many of these Pythium spp. 

One of the seed treatment compounds is Acceleron®, as marketed during the 2014 season, it had the following rate of metalaxyl (0.375 oz/cwt), pyraclostrobin (0.6 fl oz/cwt), fluxapyroxad (0.24 fl oz/cwt), and the insecticide imidacloprid (2 fl oz/cwt).  We evaluated this base treatment and the base plus another full rate of metalaxyl (1.5 fl oz/cwt) in three fields with a long history of stand losses from Phytophthora sojae or P. sojae plus Pythium spp.. 

The short story here is that the extra metalaxyl  in the Acceleron package was not needed in all 3 locations where this study took place in 2014. 

There was no significant difference in stand between the two varieties that were used in this study nor in the seed treatments.  For all three locations, there was no significant difference in yield for the seed treatment.  However, the two varieties were different, the variety with the best resistance package for P. sojae yielded 6 to 7 bu/A more that the variety with the “middle of the road” resistance package.

Based on this data – we will adapt our recommendations for the 2015 season for those areas in the state that have the highest disease pressure from Phytophthora sojae.  The Acceleron package that was marketed in Ohio during 2014, the base with the 0.375 fl oz/cwt combined with pyraclostrobin was enough to manage Phytophthora sojae and the Pythium spp. that cause seed and seedling damping-off.

1.       This is another example of where the best resistance is going to win every time, so choose the best resistance package – a Gene (Rps1c, 1k, 3a, 6, or 8) and the highest partial resistance (field tolerance).

2.       Growers/Seed Dealers will not have to add additional metalaxyl to the Acceleron treated seed bound for Ohio.  Based on these 3 field sites with very high, moderate, and low disease pressure for the 2-weeks after planting, we did not see a benefit of the added metalaxyl. 


Wood (OARDC)

Van Wert


AG2933 – Acceleron Base




AG2933 – Base plus 1.5 fl oz metalaxyl




AG3432 – Acceleron Base




AG3432 -  Base plus 1.5 fl oz metalaxyl




P value for Seed treatment




P value for Variety





Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.