Cleorina leaf beetles

Cleorina spp.

Beetles feeding on walnut leaves

Crops: Apples, walnut

Why is it a problem? Cleorina leaf beetles are not normally a serious problem in apples but can cause localized damage to developing apples and occasionally completely defoliate young trees.

Where and when is it a problem? This beetle can be commonly found in all apple and walnut growing areas. They can appear quite suddenly from late May onwards, but rarely in sufficient numbers to cause significant damage. They usually disappear in late July.

IDENTIFICATION

Damage to apple fruit
Damage to walnut fruits
Leaf dying caused by damage by beetles

Cleorina leaf beetles typically have a distinct, often metallic, coloration and a compact, oval shape common to many leaf beetles. There are two species, but they look very similar and are managed in the same way. Adult beetles are quite small, slightly larger than the head of a match stick. They are blackish-blue or dark metallic green. Beetles are very active and fly away as soon as the tree is disturbed. Alternatively, they drop down when provoked. Both species are gregarious and can be seen in small groups on leaves. Larvae have never been found in association with apple or walnut trees.

SYMPTOMS

These beetles are gregarious leaf-feeders that are normally only seen on young apple trees. They usually start feeding on young leaves on the tips of branches, ultimately skeletonizing them (leaving just the veins). They also feed on the outer skin of marble-sized apples. Heavily attacked apples will turn completely brown and rough and will eventually drop.  Because of their gregarious behavior, only a small number of the available apples (up to 20–30) are normally damaged. They can’t feed on mature apples as the skin is too hard.

In walnut trees, the leaves are very sensitive to the damage caused by the beetles as they dry up, starting from the edges, and turning black.

Confusion with other pests: Other pests also attack developing apples, including the flat spiny caterpillar and the green apple weevil. Two-spotted beetles also skeletonize leaves. However, the Cleorina leaf beetle adults are distinctive.

BIOLOGY

Lifecycle: Beetles occur in large numbers from late May onwards on the foliage of apple and walnut trees, probably coming in from adjacent forests. They usually disappear in late July. Their lifecycle is unknown.

Dispersal: Cleorina leaf beetles don’t breed on apple or walnut trees. Adults, therefore, fly in from their breeding hosts each May.

When can damage be expected? Damage is only seen from late May to late July.

Hosts: Adults are known to feed on apple and walnut trees. The breeding host is unknown.

MANAGEMENT PRACTICES

The Cleorina leaf beetle is one of several pests that can affect young orchards and developing apple fruit. The pest is transitory, but regular monitoring and rapid response are necessary to prevent significant losses if pest numbers are high.

Monitoring

Beetles can appear quite suddenly, so monitoring should be regular (three times per week) from May to July as part of broader monitoring of orchard pests (including the flat spiny caterpillar and apple fruit borer). When monitoring multiple trees, as the pest is often aggregated: just because one tree is heavily attacked doesn’t mean other trees are.

Effect of variety

Not known.

Non-chemical management

  • Manual control (removing and destroying adults) is possible if only a small number of trees are affected, but it will need to be repeated for quite some days. Adults are easily disturbed, so avoid allowing them to drop to the ground and escape.

Chemical management

  • The use of insecticides in orchards should be minimized at all times to prevent outbreaks of new pests such as red spider mites. Apple trees should never be sprayed with insecticides during flowering.
  • Spraying may be necessary for young apple trees if many leaves have small groups of beetles and the skeletonizing of the leaves starts. Also, on adult trees, large numbers of beetles can be seen feeding on large numbers of small apples.
  • Only a single spray is generally needed, as the pest is transitory.
  • Spraying should only be conducted early in the morning when these beetles are still slow and do not fly or drop away.
  • Use Chlorpyrifos (4 ml in 1 liter of water) or Cypermethrin (1 ml in 1 liter of water)

Version: NPPC 2017. Cleorina leaf beetles V1.0. Bhutan Pest Factsheet. www.PestsofBhutan.nppc.gov.bt. Date produced: 14 April 2017. Late date modified: March 1 2024 Contact: nppcsemtokha@gmail.com

Image acknowledgements: NPPC.

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