Sawflies are a type of insect that can infest gardens and cause damage to plants. They are part of the Hymenoptera order and are not actually flies, but rather relatives of wasps and bees. Sawflies can infest a wide range of plants, including fruit trees, shrubs, and ornamental plants. The larvae feed on the leaves and stems of plants, causing significant damage if not controlled.
Symptoms
- Irregular holes or notches in the leaves of infested plants
- Distorted, curled, or wilted leaves
- Large amounts of leaf debris under infested plants
- Black, sticky, sooty mold on leaves or fruit
- Clumps of sawfly larvae, often in groups, feeding on the leaves
- Stunted growth or defoliation of infested plants
- Yellowing of leaves or branches
- Presence of pupae or cocoons near or on infested plants
- Increased plant stress and reduced flowering or fruiting.
What is a Sawfly
- Body: slender, worm-like body, usually about 0.5 to 1 inch in length
- Color: Depending on species, sawflies can be green, yellow, black, or a combination of these colors
- Head: small, with chewing mouthparts and short antennae
- Wings: Transparent, with two pairs, folded when at rest
- Legs: Six, with spiny appearance to help with grasping and crawling on plants
- Abdomen: elongated, segmented, and tapered
- Ovipositor: Sawflies have a long, serrated “saw” at the tip of their abdomen used for laying eggs in plant tissue.
Note: The appearance of sawflies can vary depending on the species and stage of development. In the larval stage, sawflies resemble caterpillars, while adult sawflies resemble flies or wasps.
Treating a Sawfly Infestation
It may be necessary to use multiple methods to effectively control sawfly infestations in a garden. For example, a combination of physical removal and biological control may be effective in reducing the population, while chemical control may be necessary to eliminate a heavy infestation. Each garden and situation is unique, and it is best to consult a local gardening expert or extension service for specific recommendations for your area.
Physical removal
- Handpicking: Look for sawfly larvae and eggs on the undersides of leaves and pick them off. Place them in a bucket of soapy water to kill them.
- Water blast: Use a strong spray of water from a hose to knock sawfly larvae off of plants. This is best done in the morning when larvae are more sluggish.
- Sticky barriers or tape: Wrap sticky tape around tree trunks or place sticky barriers on plants to trap adult sawflies before they can lay eggs.
Biological control
- Encouraging predators: Provide bird feeders, nesting boxes, and water sources to attract birds and other predators to the garden.
- Parasitic wasps: Purchase and release parasitic wasps, such as Ichneumon wasps, that specifically target sawflies.
- Nematodes: Apply nematodes, which are tiny beneficial worms, to the soil to attack sawfly larvae.
Chemical control
- Insecticidal soap or horticultural oil: Apply an insecticidal soap or horticultural oil to the leaves and stems of infested plants, making sure to cover both the top and bottom of the leaves. Repeat applications may be necessary.
- Systemic insecticides: Apply a systemic insecticide to the roots of plants, which will be absorbed by the plant and provide long-term protection against sawflies.
- Broad-spectrum insecticides: Use a broad-spectrum insecticide, such as pyrethroids, to kill both sawfly larvae and adult sawflies. Be sure to follow the label instructions carefully and avoid applying when honeybees are actively foraging.