HPPD Injury to Soybeans

Chris Boerboom, Extension Weed Scientist

Just a quick reminder that the HPPD-inhibiting herbicides (Callisto, Impact, and Laudis) have postemergence activity on soybeans. Consequently, relatively small amounts of tank contamination can cause visible injury to soybeans (Fig. 1). As these are pigment inhibiting (or bleaching) herbicides, symptoms may range from minor chlorosis to bleaching. Often the chlorosis is interveinal and greater towards the leaf margin. With higher rates, necrotic tissue may occur around the leaf margin. Leaves that develop after the time of the contaminated application will show the greatest injury. 

Certain nutrient deficiencies such as potassium or manganese deficiencies may mimic the symptoms of HPPD tank contamination, but these few key features will likely provide simple clues to distinguish between the two.

1. Chlorosis appears within several days after a herbicide application.

2. Callisto, Impact, or Laudis were applied by the sprayer prior to when the soybean field was sprayed.

3. The chlorosis has a pattern consistent with the spray application. Injury may appear or be more severe in areas where the boom was first charging, in streaks where the boom overlapped, and in overlaps in the headlands or in point rows.

The degree of spray tank contamination will determine the severity of soybean injury. Predicting the final impact on the soybean yield will therefore depend on the severity of injury and how favorable the rest of the growing season is. In most cases, I would expect the soybeans to recover from most of this injury, but some areas with overlaps may suffer some yield loss. Fortunately, these areas should be a smaller portion of the field in most cases.