Pear and Cherry Slugworm

Caliroa cerasi

Pear and Cherry Slugworm, Pear Slugworm, Cherry Slugworm, Slugworm

Caliroa annulipes 2 beentree by Beentree (CC BY-SA 3.0)
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A close up of Caliroa annulipes oak slug sawfly larvae eating away at the surface of a leaf
Caliroa annulipes 2 beentree by Beentree (CC BY-SA 3.0)
1 of 3
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.

Traits

Larval grazing dries and kills the leaves.
Adult sawfly are pollinators.

Appearance

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.

Symptoms

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.

Activity

Diurnal

Personality

Order

Hymenoptera

Family

Tenthredinidae

Metamorphosis

Complete

Distribution

Europe and North America

Biological treatment

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.

Chemical treatment

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.

Attracts

Larvae will readily eat the leaves of cherry, pear, hawthorn, plum and Cotoneaster.

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