Several calls were received from consultants, advisors and Extension agents last week concerning grasshopper control.
Reports indicate that numerous early instar grasshoppers and nymphs are present in reduced-tillage fields that are receiving burndown herbicides.
There are also reports of large adult grasshoppers present in wheat in the southern area of the state.
Based on experiences during the past 10 or so years, it is suggested that where grasshoppers have been a concern in reduced-tillage fields of seedling cotton, the best time to control is when applying winter weed burndown.
Grasshoppers are a “risk” insect when cotton is in the seedling stage. With today’s seed and technology costs at planting, we must manage this risk just as we manage our in-season insects.
I do not know of any established thresholds. This problem is much greater in reduced-tillage in the central and southern areas of Alabama.
The immature stage of grasshoppers are much easier to control in March and April than the adults will be in May. Most all labeled cotton insecticides, at the lower labeled rates, give good control of immature grasshoppers.
Control can be achieved for as little as 50 cents to $1 per acre with some chemistries, by mixing with the burndown herbicides. If that window is missed, broadcast applications behind the planter would not be too late if planting in April.
The addition of Dimilin, at 2 ounces per acre, would give residual control when applications are made in March or early April.
Dimilin would provide control of later emerging grasshoppers or those that might migrate from field borders.
No highly effective controls have been found for adult grasshoppers that may be present in May.
Cotton is susceptible to grasshopper chewing on the stalk, just above the soil line, until plants reach the fifth to seventh true leaf stage.