Pear and Cherry Slugworm
Pear and Cherry Slugworm, Pear Slugworm, Cherry Slugworm, Slugworm
Caliroa cerasi is a species of sawfly closely related to wasps; however, they lack a typical 'wasp waist'. Adult sawflies look like large, slender flies; whereas the larvae, look a little bit like small, slimy black slugs, which is where this insect gets its name. The larvae of this sawfly will readily demolish the leaves of cherry and pear tree but have been known to infest hawthorn and plum too. These larvae graze the upper surfaces of leaves, exposing the inner tissues. Following feeding the leaves soon dry out and turn brown.
Larval grazing dries and kills the leaves.
Adult sawfly are pollinators.
Adults become active in June. They look like black-slender flies, these only grow as large as 0.5cm. Larvae look like black slugs. They're club-shaped and appear slimy. There can be as many as three generations a year.
Larvae graze leaf surfaces, leaving only the inner tissues. Leaves quickly dry-out, turning brown. This type of damage is known as window paining. You may see slimy black larvae on the leaves of hosts, which may appear unsightly. In worst cases the tree may become slightly defoliated.
Europe and North America
It's known that the damage caused by these pests is tolerable. Trees can survive infestations even when they're especially heavy, and tree health is almost always sustained. These caterpillars have natural enemies which help control their numbers. If feasible, these insects can simply be picked off and placed on an elevated surface for the birds.
It's not recommended to treat plants with Caliroa cerasi present. Infestations are seldom severe, and larvae are a resource for wildlife. Organic pyrethrums are proposed as more environmentally benign than synthetic insecticides. The active compound is acquired from Chrythsanthiums; it's unselective to the insects who ingest it. Synthetic pyrethroids are more aggressive in their mode of action but can be applied to plants less frequently. They are analogues of organic pyrethrums, tending to persist longer in the environment. They generally contain compounds deltamethrin and cypermethrin. Please consider if chemical control is essential. If a chemical option is sought, check with your local garden centre and please take care to follow the manufacturers' instructions. Check with your local regulating body for guidance on active ingredients and their authorisation for use. Feel free to as the Candide community if you ever feel unsure.
Larvae will readily eat the leaves of cherry, pear, hawthorn, plum and Cotoneaster.