Pear slug sawfly: how to recognise and treat it

Pest

Pear slug sawfly — Photo: Didier Descouens, CC BY-SA 4.0, Wikimedia Commons

Symptoms

Slimy, slug-like dark larvae up to about 10 mm long on the upper side of the leaves.
The upper leaf surface is grazed away between the veins.
The grazed patches dry up and turn brown or grey.

Organic treatment

Pick off the larvae by hand or knock them off with a strong jet of water.
Spray insecticidal soap, neem oil or horticultural oil, wetting the larvae thoroughly.
Bacillus thuringiensis does not work, because the larvae are not caterpillars.

Chemical treatment

Spinosad, not on plants in flower because it is toxic to bees; follow the label dose and pre-harvest interval.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

Check the leaves from April onward, as there are two or three generations a year.
Tolerate light damage; it rarely harms the tree or the crop.
Encourage birds and ground beetles that eat the larvae.

Plants it affects

Sources

Figures checked against these sources.