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Sawflies - forwardone - 11-29-2006 01:17 AM

Look for

Leaves that become skeletonised or transparent with just their veins remaining tend to be the work of sawflies, which eat through the tissue of the leaf until it has almost completely disappeared. The larvae can often be seen around the edges of the leaves and most curl up into an S-shape when disturbed. Larvae will also bore into developing fruits causing them to become scarred and exude sticky liquid.

Plants affected

* Sawflies affect a number of different plants but different types tend to affect different crops. Some of the most common are the apple sawfly (hoplocampa testudinae), the common gooseberry sawfly (Nematus ribesii), the turnip sawfly (Athalia rosae) the pear and cherry 'slugworm' (Caliroa cerasi), the rose slug sawfly (Endelomyia aethiops), also known as the rose 'skeletoniser'.

About sawflies

* Adult sawflies are usually inconspicuous flying insects with two pairs of wings and often dark coloured bodies and legs. They resemble flying ants but have no 'waist' between thorax and abdomen.
* They're often seen flying on warm sunny days in spring at blossom time when they usually feed on pollen and nectar.
* The adults live for about two weeks, during which time they mate before the females start laying eggs into plant tissue.
* Eggs are inserted into cuts on the leaf surfaces that the female makes with her saw-like ovipositor.
* Eggs hatch into larvae that resemble moth caterpillars, although they have more pairs of 'pro-legs' on their abdominal segments.
* The larvae usually feed in groups on leaves and fruit of plants.
* When disturbed, the larvae of most sawfly species adopt an S-shaped pose, often raising their rear ends and waving them about.
* At least 400 different species of sawfly have been recorded on plants in Britain.
* Larvae usually feed for about four to five weeks before pupating in the soil.
* Infestations of sawfly larvae often defoliate plants although infestations are usually localised and rarely devastating.
* Two or three adult generations may develop during the growing season with the third generation overwintering as pupae that emerge in the spring

Treatment:-

Chemical

Products containing the following chemical ingredients are all effective on sawflies:

Rotenone
Pyrethrum

Note: It is important to read manufacturers instructions for use and the associated safety data information before applying chemical treatments.

Organic

* Inspect bushes every week from April/May onwards for the signs of sawfly infestation then search for the larvae and remove by hand.
* Tell-tale signs include transparent patches on leaves where young larvae are feeding; seeping sap, where the insects have damaged plant tissue as they lay eggs; areas of defoliation or skeletonised leaves.
* Position susceptible plants in an open position where birds can easily feed on the larvae.

Prevention

* There's no sure method for preventing infestations. However, regular checking and spraying with a rotenone-based chemical can reduce severity of an attack.
* Select varieties that are reported as less susceptible to attack, particularly roses and apples.