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Apple sawfly

Apple sawfly larvae can damage apple fruits at the fruitlet stage in late spring to early summer, affected fruits usually drop off in June. This should not be confused with 'maggoty' apples in late summer which are due to  codling moth.

Internal damage caused by apple sawfly larvae.

Quick facts

Common name Apple sawfly
Latin name Hoplocampa testudinea
Plants affected Apple fruits
Main symptoms Holes in fruitlets that fall from the tree in early summer; elongate ribbon scars on mature fruits
Caused by Caterpillar-like larvae of a sawfly
Timing Late April-June

What is apple sawfly?

The caterpillar-like larvae of apple sawfly initially tunnel beneath the skin of developing apples, causing a scarring, before burrowing into the fruit. Adult apple sawflies are small winged insects with blackish brown heads and thorax and brown abdomens. Sawflies are in the same order of insects as bees, ants and wasps (Hymenoptera).

Symptoms

Signs of apple sawfly include:

  • In late May and June, damaged fruitlets have obvious holes with the larva’s blackish-brown excrement pellets spilling out
  • Each larva can damage several fruit
  • Affected fruitlets usually drop off the tree as part of the June drop (when apple trees shed excess fruits)
  • Fruitlets that suffered only initial feeding damage by a sawfly larva can stay on the tree and develop as fruits. These fruits are usually misshapen and have a long ribbon-like scar about 4mm wide, often starting at the eye end of the fruit and extending around the circumference. The fruit is usually still edible when this occurs

Control

Apple sawfly is as widespread as codling moth. However, the presence of apple sawfly can usually be tolerated and in years when there has been a heavy fruit set, a bit of fruit thinning caused by apple sawfly can be beneficial.

Some cultivars, such as ‘Worcester Pearmain’, ‘Charles Ross’, ‘James Grieve’ and ‘Ellison’s Orange’, seem to be particularly susceptible to apple sawfly. Apart from ‘Early Victoria’ and ‘Edward VII’, cooking apples are rarely affected.

Check apples once fruit has begun to set so action can be taken before a damaging infestation has developed. When choosing control options you can minimise harm to non-target animals by starting with the methods in the non-pesticide control section. If this is not sufficient to reduce the damage to acceptable levels then you may choose to use pesticides. Within this group the shorter persistence pesticides (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife than those with longer persistence.

 

Non-pesticide control

  • Where possible tolerate populations of sawfly
  • Encourage predators and other natural enemies of sawfly in the garden, such as birds and ground beetles
  • Pick off damaged fruitlets when they are seen to prevent the larvae moving to other fruitlets or going into the soil to pupate.

Pesticide control

  • If damage has been heavy in previous years, a spray within seven days of petal fall with the contact pyrethroid may control the newly hatched larvae. Spraying at dusk is likely to give the best results
  • Organic contact insecticides containing natural pyrethrins (e.g. Bug Clear Gun for Fruit & Veg, Neudorff Bug Free Bug and Larvae Killer). Several applications of these short persistence products may be necessary to give good control
  • More persistent contact insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Bug Killer) and deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer, Provanto Sprayday Greenfly Killer)
Follow label instructions when using pesticides. Make sure apple or all fruit and veg is listed on the label and follow instructions on maximum number applications, spray interval and harvest interval

Plants in flower should not be sprayed due to the danger to bees and other pollinating insects

Inclusion of a pesticide product does not indicate a recommendation or endorsement by RHS Gardening Advice. It is a list of products currently available to the home gardener

Download

Pesticides for gardeners (downloads pdf document outlining pesticides available to home gardeners)

Biology

Adult apple sawflies are active in late April-May and can be seen visiting the open blossom. They are 4-5 mm long, the head and thorax are blackish brown and the abdomen is brown.

Eggs are laid at the base of the flowers. After petal fall, the eggs hatch and the caterpillar-like larvae start feeding. Initially the larvae tunnel beneath the skin of the developing fruitlets. Later they bore into the core of the fruitlets, and this feeding damage causes affected fruit to drop in early summer. If the larva dies before reaching the core, the fruit can survive and develops but has a ribbon-like scar on the skin where the early feeding took place.

When fully fed, the larva is about 10mm long and has a brown head and white body. Each larva can damage 3-5 fruitlets before it completes its feeding and goes into the soil, where it overwinters as a non-feeding larva and pupates in the following spring.

See also...

Big Garden Sawfly Survey (External link)


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