Hymenoptera – Sawflies and Horntails

In the order Hymenoptera are sawflies and horntails (a type of wasp) which as a group are pests that cause a lot of damage to trees, shrubs, grasses (both residential and agricultural), raspberries and roses. The only exception are the sawflies in the family Orusidae, who themselves are parisitoids and attack wood borer beetles and horntails. These beneficials are found in many forested areas of California and help control these pests.

Life Cycle
Female sawflies deposit their eggs in slits cut into the foliage of trees or shrubs, but a few attack grasses, raspberries and roses. Sawflies are usually plant specific. Once the larvae emerge, they begin to feed on the leaves, pollen, or buds, causing unsightly damage. The larvae look like large caterpillars with more than 5 pairs of legs and only 2 simple eyes. They may be brightly marked with spots or stripes. Many of those that feed on conifers build webs or tents in which to feed. After feeding for three to four weeks, mature larvae spin a cocoon that turns brown and resembles a bud tip. Most fall to the ground. The adult will emerge from the pupal case and start the life cycle again. Most sawflies have one generation a year; some have two.

Sawfly and Horntail Control

• Trees and shrubs tolerate moderate defoliation.
• Prune damaged foliage and stems.
• Parasitic wasps, predaceous beetles, or fungal and viral diseases commonly kill sawfly populations. If damage is not severe, you may need to do nothing. Monitor the situation.
• Insecticidal soap or Horticultural Oil kill exposed sawfly larvae but may damage blossoms.
• BioNeem and other Neem oils will stop the larvae if you spray early enough; they will need to be absorbed by the plant and then be ingested by the larvae to be effective.
• Apply Entrust as directed to control sawfly

Monitor areas with traps to warn of adult sawfly presence and to predict possible presence of larvae, especially with conifers or if wheat fields may be at risk. View Borer Control Products.