Stahnke's chemical trials of crane fly controls over the years have allowed her to devise three different treatments, one for different times of the year and different larval sizes. It is important, once the presence of crane flies is established, to get in the habit of monitoring them and determining which of the three control methods to use. If the last 45 years are any indication, this will continue to be a long-term problem.
The first control option takes place during the adults' oviposition phase in the fall. In her location, Stahnke says this is about September 15. There are two interchangeable insecticides that have proven to give 75 percent control of larvae at this point: imidacloprid (Merit) and thiamethoxam (Meridian). These are "least-toxic" formulations that give good control at labeled rates and have a short residual period. Stahnke points out that this treatment will not work if they are used at one of the other time periods. A 75 percent control level works out pretty well, as she calculates that birds eat about 30 percent of the larvae in any case.
The second control window is around November 15, when the larvae of the ECF are at the second instar level. Dursban used to be Stahnke's insecticide of choice here, but it is no longer registered for home and commercial lawns. At this point she recommends four insecticides. The first is bifenthrin (Talstar in formulations FL, PL and EZ; as well as Onyx and One), and the second, although it may go off the market in the future, is carbaryl (Sevin SL). At this time of the year those two chemicals have been shown to give control in the 85 percent range in her tests. The last two formulations, a mix of clothianidin and bifenthrin (Aloft), and clothianidin by itself (Arena), provided 95 percent control and 75 percent control, respectively.
The third control period is from February to mid-March, when the ECF is in its fourth instar and the CCF is in its third instar. Again carbaryl (Sevin SL) will achieve 60 percent control even at a low application rate, which is generally adequate with birds feeding on the larvae. Another chemical effective at this time is bifenthrin (Talstar), which has given her almost a 90 percent control rate in her trials. A third is indoxacarb (Provaunt), and a fourth is chlorantraniliprole (Acelepryn). The last two are new products that both provided about 95 percent control.