Pyracantha Leaf Miner

Disease Information

Pyracantha Leaf Miner

The Leaf Miner Phyllonoryceter leucographella

DESCRIPTION OF THE PEST

Pyracantha(Firethorn) Leaf Miner Phyllonoryceter leucographella is the larvae of a moth of the Gracillariidae

This moth lays their eggs on the midrib of leaves of Pyracantha. They are pale green, about 0.2 mm long, and only just visible to the naked eye. Usually there is only one egg, but if the infestation is heavy there can be many eggs per leaf.

Symptoms and damage

As the eggs hatch the larva mines the leaves of Pyracantha and other rosaceous bushes. The larvae starts by eating either side of the midrib of the leaf. When they are ready they spin a cocoon inside the mine and pupate, during this time the leaf may curl up which may hide the larvae and mine. The adult emerges leaving the empty pupal case sticking out of the now deserted leaf-mine. There can be three or more generations per year. They also overwinter in the mines of the leaf.

Management

Leaf miners are difficult to control since they spend most of their life inside the leaf protected by the epidermis cells of the leaf.

Timing of insecticide sprays is essential if control is to be obtained and must be done before the larvae enters the leaf surface (normally in early April). Picking off infested leaves the spring if the infestation is not too heavy will reduce subsequent attacks. Leaf miners populations vary greatly from year to year and they do not kill the tree, but do make the leaves look bad. Once inside the leaf only systemic insecticides will get to the miners.

Spraying the plant with insecticidal plant oils should prevent many eggs from hatching if done early enough. Two or three applications may be needed in a season, being careful not to spray when beneficial insects are around. Companion planting can reduced or prevented Leaf miner infection by planting trap crops near the plants to be protected. Some leaf miners may be trapped by pheromone fly traps hung around the plant.

 



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