Gooseberry Sawfly

Gooseberry Sawfly

Our Pests (Late May2017)

From Royal Horticultural Society

Gooseberry sawfly

The common gooseberry sawfly is one of several sawfly species that can attack gooseberry and red/white currant during spring and summer.

Common gooseberry sawfly (Nematus ribesii) on Gooseberry (Ribes uva-crispa). Credit: RHS/Entomology

Quick facts

Common name Common gooseberry sawfly, spotted gooseberry sawfly and small gooseberry sawfly
Scientific name Nematus ribesii, Nematus leucotrochus and Pristiphora appendiculata
Plants affected Gooseberry, red and white currants
Main symptoms Foliage is rapidly devoured by caterpillar-like larvae that are green with black dots
Most active April to September

Symptoms

  • Severe defoliation of the bushes can be caused by the caterpillar-like larvae of one of three species of sawfly
  • Larvae of the common gooseberry sawfly are up to 20mm (almost ¾in) long, pale green, with many black spots, and black heads  The adults are winged insects;  females are 5-7mm (up to ¼in) long and are yellow with black heads and black markings on the thorax; males are similar but more extensively marked with black, including the upper surface of the abdomen
  • Larvae of the pale spotted gooseberry sawfly are slightly smaller than those of the common gooseberry sawfly and have pale green heads. It has one generation a year with larvae present in May and June
  • The small gooseberry sawfly can have up to four generations of pale green larvae from late April onwards
  • The larvae of some moths may also eat the foliage of gooseberries and currants

Control

Non-chemical control

  • Regularly check the plants from mid-April onwards for sawfly larvae and pick them off by hand
  • A biological control (pathogenic nematode), sold as Fruit and Vegetable Protection, can be watered onto infested plants. The nematodes enter the bodies of the sawfly larvae and infect them with a bacterial disease. This nematode is available from some garden centres or via mail order. The nematode should be applied during cool damp weather

Chemical control

  • Spray when young larvae are seen, with an insecticide approved for use on the appropriate food plant. Make sure that the manufacturer’s instructions regarding maximum number of applications and harvest interval are followed
  • Suitable insecticides include the contact pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), deltamethrin (e.g. Bayer Provado Ultimate Fruit & Vegetable Bug Killer) or an organic pesticide such as pyrethrum (e.g. Defenders Bug Killer)
  • Plants in flower should not be sprayed due to the danger to pollinating insects
  • Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

Biological control suppliers (Abode Acrobat pdf)

Biology

  • The common gooseberry sawfly is the most troublesome pest of gooseberries. It can have three generations a year, with the larvae active in late April to June, July, and August to September
  • The female sawflies lay eggs on the underside of leaves, low down in the centre of the bush, so the young larvae go unnoticed until they have eaten their way upwards and outwards, devouring the leaves as they go
  • Defoliated plants are weakened and may produce a poor crop the following year
  • When the larvae are fully fed, they go into the soil, where they spin silk cocoons and pupate
  • The pale spotted gooseberry sawfly only has one generation a year with larvae present in May and June
  • The small gooseberry sawfly has up to four generations a year with larvae present from late April

Nematus leucotrochus is a species of sawfly in the family Tenthredinidae, known as the pale-spotted gooseberry sawfly. Widespread throughout central and northern Europe, this insect is best known as a pest of gooseberries. The larvae feed on the foliage of the plant, defoliating it. Unlike Nematus ribesii, the common gooseberry sawfly, the species has a single brood. Adults appear in early May and larvae in May and June

 

 

 


Advise

To prevent gooseberry sawfly caterpillars, pick a bucket of foxglove leaves and pour over two pints of boiling water, leave for two days, strain and spray on gooseberry plants before any caterpillars are seen.

Foliar drenches of Nemasys Caterpillar Killer, carefully timed in early May and July, will apparently solve the problem. Supplies from, among others, Green Gardener (01603 715 096; www.greengardener.co.uk)

I used Pyrethum powder (Py?) which helped kill them off, but the caterpillars pupate in the soil over winter then crawl up the “trunk” the following year, (or something like that!)  anyway I put weed membrane down which interrupts this lifecycle

I’d fork gently over the root area in the autumn to expose the over-wintering pupae to hungry birds.

If you’re picking them off the plant, spread newspaper underneath first.  They respond to vibration by dropping off onto the soil, where you can’t find them…

As soon as I spot them, I spray the bush with thick soapy water and squish them all dead !

The traditional way is to turn the family chickens into the fruit garden over the winter to scratch around in the soil and get the pupating grubs.  I don’t keep chickens any more, and luckily we’ve escaped the sawflies in this garden.

I’ve made up a spray of neem oil and as soon as all the leaves are out in April I drench each bush. Any spare solution goes onto the soil below the plant as the earthworms are supposed to love it. I do a second drench at the end of May (just in case) and have had great crops since.

Neem is totally organic and although it stinks a bit is easy to mix up and apply . I got mine off ebay …. wasn’t expensive for a big bottle which will last ages. At room temperature it is solid, but goes liquid again with a couple of hours in the airing cupboard.

Am using this year on the lilies as the dreaded beetle has now put an appearance in Scotland.

Just a shame it doesn’t work on slugs ….

http://www.discoverneem.com/neem-repellent.html

See this link for how to make the spray.

http://www.discoverneem.com/neem-insect-spray.html

I start when the leaves first come out which is usually April round here …. and I give them a good dousing every 4 weeks or so until end August. It’s a quick job  … and also seems to stop them getting attacked by aphids.