Fungicide Phytotoxicity: Check the Fungicide Applied Prior to Blaming SDS

Severe phytotoxicity associated with a foliar fungicide application.

Several products can produce a phytotoxic response on soybean plants following a fungicide application.  Based on trials conducted over the past two seasons in Starkville and Stoneville a total of six fungicides have been observed to produce phytotoxicity following the application (Fungicide phytotoxicity).  The response on the plant can vary not only due to the particular variety planted, but also due to the environmental conditions at the time of application.  However, additional fungicides may produce a phytotoxic response.  The list I have included only presents the fungicides I have personally observed to result in a phytotoxic response.

Presently, the phytotoxicity associated with a fungicide application is not believed to result in a yield reduction.  However, little effort has been made to attempt to correlate a yield reduction to the potential phytotoxicity associated with particular fungicide products.  Trials conducted during 2013 suggested that even products that produced severe phytotoxicity (> 50% of the plot affected) still produced a yield greater than the average of the fungicides applied in small plot trials.  The attached figures present a scatter plot of the phytotoxicity (% phytotoxicity) versus yield (bu/A).  The majority of the fungicides applied at the two locations included in figures did not result in fungicide phytotoxicity and therefore the phytotoxicity result will be a zero, as observed on the far left of the figure.

2013 Starkville, MS R5 fungicide trial.

2013 Stoneville, MS R5.5 fungicide trial.

Trials are ongoing this season with similar fungicide product combinations.  Additional data will be available this fall and winter regarding products that result in phytotoxicity.