Pyracantha Leaf Miner
The Leaf Miner Phyllonoryceter
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.
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.