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Leaf Blotch Miner Moth

Gracillariidae

Leaf Blotch Miner Moth, Leaf Blotch Miner Moths, Leaf Mining Moth, Leaf Mining Moths

A close up image of a leaf mining moth from the insect family Gracillariidae

Caloptilia azaleella

by Lymantria. CC BY-SA 3.0

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Gracillariidae is an insect family containing some of the Leaf Mining Moths. Several species are important pests of shrubs, trees and herbaceous plants- some of which, are invasive. A female will lay eggs in the host plant (i.e. caterpillar food plant), and when hatched, the caterpillars bore into the leaf. As they feed on the inner plant tissue, it's possible to trace the pattern of movement through the tunnels they leave in their path. There are 95 species in Gracillariidae currently present in the UK and Ireland.
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Traits

Mined leaves are unattractive.
Tree and plant health is unaffected, in most cases.

Appearance

Adults: Moths in the family are tiny (wing length: 2-8mm). When at rest, the wings appear in a steep incline, with each wing coming together to form a roof-like structure. The wing shape is elongate, narrow and long. Colour and pattern can be variable. Larvae: Caterpillar larvae are typically colourless when first hatched. With each successive moult, they turn yellow, orange, white or green, and always slightly translucent. They appear like tiny, ovular maggots. Pupae: The cocoon-like structures look like tiny, brown, ovular pellets. They sometimes appear within the leaf mine, but some stick to the outer leaf beneath a thin membrane and sticky silk, others can drop to the floor; with the remaining pupating within rolled-up leaf margins.

Symptoms

Faded, meandering lines on the surfaces of leaves and pea pods are a tell-tale sign that a leaf miner insect is present. Mines are characteristic of a species, so their qualities are vast. Brown, white, silver, or yellow blisters and patches may be evident on leaves. Some insects can create multiple mines on one leaf; others only create a single mine. Feeding punctures on the surfaces of foliage. Cells begin to die around the mines, resulting in brown patching. Larvae can sometimes be seen in leaf mines when the leaf is held over some light.

Activity

Crepuscular

Personality

Order

Lepidoptera

Family

Gracillariidae

Metamorphosis

Complete

Distribution

Gracillariidae occurs worldwide, excluding Antarctica.

Biological treatment

Dealing with a Leaf Miner infestation can be tricky because the plant leaf itself protects them. Upon detection of a Leaf Mining pest, you should make an effort to remove the damaged leaves, making sure to squish any larvae or pupae before disposal. Always dispose of leaves in with the landfill. Never bin them in compost or food waste bins! Practise crop rotation annually. Pupae can sometimes lie dormant in the soil over winter when conditions are unfavourable. So by rotating your plants, you are making life more difficult for these insects. If you own a greenhouse or are a greenhouse grower, sticky traps are an effective and cheap way to monitor what insects are about. You can use physical barriers to prevent insects from laying eggs on plants. E.g. insect-proof netting can be useful when used on small trees and vegetable plants. On the other hand, using row covers and plastic sheeting can stop any pupae falling into the soil, disrupting the life cycle. Attract beneficial insects into your green spaces by planting indigenous plants, herbaceous-wildflower borders, bug hotels, or just by letting some areas grow a little wild! Likewise, birds are top predators of moths and leaf-mining insects. Incorporate bird feeders to encourage birds into the garden.

Chemical treatment

Unfortunately, no chemical treatments are effective against these insects because the leaf epidermis protects them.

Attracts

This family targets the foliage of trees, shrubs and herbaceous plants.
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