PEST
 
   NAME
     Pear and Cherry Slug
     Caliroa cerasi
 
   ORDER
     Hymenoptera
 
   FAMILY
     Tenthredinidae

Description of the Pest
The adult is a glossy black sawfly, up to 8mm long; females have an ovipositor that cuts a slit in the leaf and deposits small flat eggs, which hatch within two weeks. Newly-hatched larvae are white, and are progressively covered as they feed by a dark olive-green, slimy exudate. They resemble small slugs. At each moult they shed the slimy coat and, on maturity, they revert to their original orange-yellow colour. Larvae have chewing mouthparts.

Appearance and Distribution of the Pest
This pest appears worldwide in cool moist climates. It is distributed by flying with the assistance of wind over large areas with the first generation appearing in early summer followed by a second in summer with some of the lava overwintering underground before pupating.

Life Cycle
This insect has a Holometabolous life cycle, ie. When metamorphosis is observed during the pupal stage.
The female uses a saw-like ovipositor to cut slits into leaves, in which the eggs are deposited. Two or more generations may appear annually. Mature larvae pupate in small earthen cells under the soil.

Period of Activity
Most active from spring through to late autumn and prefers cool moist conditions.

Damage Caused
Larvae skeletonise the leaves by feeding on the upper surfaces; damaged leaves curl up and look burnt. Plants may be defoliated but rarely killed. Only young plants or trees under stress may die as a result of attack and the slug will not attack the fruit. 

Susceptible Plants
Cherries trees are most susceptible to attack but pears, peaches, plums, quinces, cotoneasters are also attacked.

Cultural Control
Remove by hand. Bare rooted plants are preferred purchases in areas of infestation, because of the risk of pupae in soil. For the same reason, bare soil beneath infested plants may be covered with fly netting, to prevent sawflies from emerging, or the soil may be cultivated to disturb and destroy pupae. 

Biological Control
There is a predator wasp (Polistes Paper Wasp) that carries the slug to its nest for its lava to feed on. Several species of bird also feeds on the lava but both wasps and birds tend to feed on heavily infested plants. This is not going to save the appearance of the damaged plant.

Chemical Control
Normally spraying is not required and spraying will kill the wasps that are helping to control the pest. If spraying is required Maldison or Carbaryl may be used. 
Note
Always read the label for registration details and direction of use prior to application of any chemicals.