- First, the established threshold is 0.5 to 1 larvae per stem. This number is obtained by sampling 100 stems in multiple locations in the field. Distribution of larvae is not always uniform across a field so make sure you sample at several locations within the field.
- The second thing to consider is what stage of crop development your field is in. Generally, we are concerned with damage through the soft dough stage. Some fields I have seen are past this stage others have not yet reached it.
- The next thing to consider is what percent of the field is showing leaf damage. Typically, we don't treat unless 10% leaf damage or greater is present. Also keep in mind that the upper most leaves are responsible for grain fill. We need to protect the flag leaf and one or two leaves below for grain fill.
- Next , we need to look at the yield potential of the crop. This is where the price of your wheat comes into play. At this stage of the game many advise that we need to be looking at protecting fields with 60 bushel or more yield potential. Keep in mind we also need to consider how much wheat will be damaged by running across the field with a sprayer at this stage of crop development.
As you can see this is not necessarily an easy decison to make at this point in time for some growers. This is a photo of cereal leaf beetle damage in wheat taken by Penn State Entomologist Dr. John Tooker.