The aim of control is to stop defoliation before it becomes too extensive. When sawfly larvae are present in high numbers, sprays are justified to protect tree health. To control sawfly larvae, spray infested evergreens with insecticides such as Orthene, Diazinon or Sevin. Even though the larvae are caterpillar-like, the natural insecticide Bt, or Bacillus thuringiensis, isn't effective on larvae or adult sawflies. Apply the spray at the beginning of an attack, while the sawfly larvae are young.
Complete coverage is important for control.
Sawflies may be seen on one tree and not others nearby. Spray ONLY the infested trees, but occasionally examine other trees for possible additional outbreaks. Sawflies are more prone to attack single landscape trees that are planted out in the open, rather than trees in a forest-like setting. Permission is hereby given to duplicate this Plant talk Colorado TM script as is if credit is given to the sources.