Welcome to my website where I gather information about plant pests and pathogens preying on gardens in my local area in Melbourne. I want to live in harmoney with nature and so I use exclusion techniques and natural predators to protect my edible and ornamental plants instead of using poisonous chemicals...................John Ashworth 27th July 2015.
For the first couple of years my dwarf pear tree was infested with pear slugs, but last year after using a monthly aerated compost tea foliar spray on the plant, the pear slug stayed away.
This may have been a coincidence and some other factor caused the slugs to stay away.
I will take extra precautions this year including:-
Thoroughly cleaning up debris from beneith the tree, to remove pupating sawfly larvae in leaf litter and mulch.
Using horticultural glue to stop the female sawfly from crawling up the trunk to mate and lay eggs.
Why Pear Slug is a Pest.
The pear slug is the larva of the sawfly, Caliroa cerasi. They are not slugs but are a kind of insect of the family Tenthredinidae.
They eat the leaves of pear trees, leaving behind skeletonised foliage. If left uncontrolled, this will eventually lead to a substantial stripping of the trees canopy and decline of the tree's overall health.
The larvae cover
themselves in green slime, making themselves unpalatable to predators.
When the larvae are fully grown, they drop off the tree onto the ground
and pupate underground or in leaf litter/mulch.
The adult sawfly emerges from the cocoon and climbs from the soil to mate. It lays eggs on the leaves of the host plant, completing its lifecycle.
Because the female sawfly climbs the tree to mate and lay her eggs, horticultural glues can be used as a protective barrier.
The simplest think to do with sawfly larvae is to keep washing them of the trees foliage with a hose whilst still imature. This is fine with a dwarf tree like mine, but a bit of a task with a full sized pear tree.
It is good practice to clear
all debris from under the tree in winter. Dispose of the debris in a
hot compost or bury it 500mm under soil where it will not be disturbed
for some time. This will help remove some of the larvae pupating during the colder months.
Apply masking tape to the trunk of the tree about 100mm above the ground and apply a ring of horticultural glue around the tree on top of the masking tape. This stops the adult female sawflies from crawling up the tree to mate and lay eggs.
The masking tape protects the bark of the tree from the glue, and makes it easy to replace the glue when it becomes covered in dust or dead insects.
Spray the foliage with aerated compost tea every month during the growing season. This seems to increase the plants resistance by toughening up the leaves or possibly supplying a microbial predator.
It remains to be seen whether the good results last year were as a result of the compost tea spraying program or some other environmental factor.