Greenbug reproduction is temperature dependent. They can reproduce at temperatures between 40 and 95 degrees F. It takes seven days of continuous temperatures of less than 20 degrees to significantly reduce their populations, and we normally do not see these kinds of temperatures here.
Mild temperatures have allowed the greenbugs to increase, but it is still too cold for the small parasitic wasp that is their primary natural enemy. We cannot expect much help from this wasp until the daytime temperatures routinely reach 65 degrees, and that is not likely for at least two to three weeks.
Growers should scout all of their fields to determine the need for an insecticide application. A “down and dirty” technique is to drive around the perimeter of the fields and look for areas where leaves are beginning to turn yellow or yellowish orange. These off color areas are usually caused by one of three factors: low fertility, plant disease, or greenbugs.
If large colonies of greenbugs are found in these areas, growers should carefully inspect the rest of the field to determine the extent of the infestation. As greenbug density increases, more plants will begin to show the typical damage symptoms.
When high numbers of greenbugs and their characteristic damage can be easily found throughout the field, an insecticide application is suggested. Populations in excess of 100 greenbugs per foot of row are cause for concern, especially in younger wheat.
A number of insecticides will effectively control this pest, but Lorsban and dimethoate are most commonly used in this area. We may reach a “damage threshold” in some fields before topdressing time, so a separate application might be necessary.
Jim Swart is an Extension IPM specialist with Texas A&M University.