A new method of controlling codling moth has been developed at WSU where timing of the sprays is altered to take advantage of the slow start of egg laying.
WSU experience with the codling moth (CM) degree-day model shows that first fruit injury is detected at 425 degree-days past January 1 (250 DD past biofix). The hatching of deposited eggs starts off slowly and in the first 10-15 days (100 DD) only about 12-15% of the total egg hatch occurs. The rate of egg hatch then becomes more rapid and in the 21 day period between 525-825 DD (350-650 DD after biofix) almost 70% of the eggs hatch. After this period of peak activity, the rate of egg hatch slows and the final 15-20% of the first generation egg hatch occurs over about a two-week period. A potential problem with a traditional larvicide application strategy is that the most active residues from the first application are in the orchard at a time when relatively little CM egg hatch is occurring. Applying an ovicide (Esteem, Intrepid, Rimon, or Altacor) prior to the onset of the egg-hatch period kills eggs that would begin hatching at 425 degree-days (250 DD after biofix). As a result growers can delay the first larvicide application until 525 degree-days (350 DD after biofix), which puts the most active residues at the beginning of the period of peak egg-hatch activity. This strategy also shortens the period of time that larval control is necessary. (PMTP Team, WSU-TFREC)