Pear Fruit Sawfly
Pear fruit sawfly (Hoplocampa brevis) is an insect whose larvae feed exclusively inside pear fruitlets in early spring. It should not be confused with a pest of a similar name, the pear sawfly (Caliroa cerasi), which feeds on foliage in the summer.
Pear fruit sawfly adults appear fly-like, but are actually small wasps that are about 3/16-inch long, and reddish-yellow in color. The larvae are also small, and are cream to yellowish-grey, with a red-brown to dark black head. When mature, they measure 1/3-inch long.
The pear fruit sawfly is an invasive insect that is native to Asia. The adult population is mostly female, and they reproduce parthenogentically (without mating). In spring, females lay a single egg within the epidermis of up to 40 pear flowers. After one to two weeks, the larva hatches and tunnels into the pear fruitlet to feed. One larva can enter and exit multiple fruits over a period of 20 to 34 days.
Once mature, the larva drops to the ground, burrows into the soil, and forms a silky cocoon. The sawflies remain underground until spring, when they pupate and emerge as adults. Approximately 25% of larvae remain in the soil an additional year. There is only one generation per year.
Only fruits are affected:
- Deformed and swollen shape
- Blemished skin
- Round hole near the calyx
- Black decay and wet frass
- Premature fruit drop
Some general practices include the following:
- Start monitoring the pear orchard for adult sawflies in March or April at three-day intervals, and continue through bloom.
- In general, the decision on whether to treat depends on the previous year’s damage, the current crop load, and the presence of adults at flowers.
- If the crop load is high, anecdotal evidence suggests that damage from pear fruit sawfly will be “absorbed” by crop thinning, and therefore, intervention may not be necessary.
- Where applicable, autumn plowing and disking between tree rows can kill larvae in the soil that are preparing for overwintering.
There are no products specifically labeled for this pest in Utah. Pear growers have reported that a thorough dormant oil plus insecticide (carbaryl, pyrethroids, diazinon) application targeting other pests reduced their losses from the pear fruit sawfly by about 90% over the prior year.
For organic control, use oil alone at the delayed-dormant stage (bud swell). The use of entomopathogenic nematodes may also be used as they target the larvae in the soil. Applying a mix of Heterorhabditis bacteriophora and Steinernema carpocapsae to the soil just before larval drop (late May to early June) can reduce adult sawfly emergence the following year. Nematodes require consistent soil moisture, however, so this practice may not be effective in Utah.