The caterpillar like larval stage of two species of sawfly can feed on Geum in spring and summer.
Latin names Claremontia waldheimii and Monophadnoides rubi
Plants affected Geum species
Main symptoms The foliage is eaten by pale green caterpillar-like larvae
Caused by Larvae of sawflies
What are Geum sawflies?
Sawflies are a group of insects suborder (Symphyta) of the Hymenoptera (bees, ants and wasps). There are about 500 species of
There are two species of geum sawflies they have pale green larva, with small white spines. The larvae reach 15 mm in length that eat the leaves of Geum plants in the spring and summer. The adult insects are about 6 mm long and mainly black.
Geum sawfly larvae initially feed concealed between the folds of unexpanded leaves. As they grow they consume large irregular holes and damage can occur very quickly and defoliation can be extensive. Signs of geum sawflies include;
- Pale green caterpillar-like larvae with small whitish spikes up to 15 mm long
- Leaves can be reduced to a network of the larger leaf veins, affecting the appearance and vigour of plants
- Affected plant often recover with no long term effects
Geums can cope with low numbers of larvae and damage can usually be tolerated and the presence of these insects treated as part of the biodiversity a healthy garden supports.
Check geums frequently from spring onwards so action can be taken before a damaging population has developed. When choosing management options you can minimise harm to non-target animals by starting with the methods in the non-pesticide control section and avoiding pesticides. Within pesticides the shorter persistence products (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife than those with longer persistence and/or systemic action. Pesticide treatments are likely to kill natural enemies and are only likely to be successful if the entire plant can be reached.
- Where possible treat this sawfly as part of the biodiversity a healthy garden can support, plants usually recover from defoliation
- Encourage predators and other natural enemies of sawfly in the garden, such as birds and ground beetles.
- Check plants regularly in May and June for the presence of larvae and remove by hand where practical
The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.
- If numbers of larvae are too high for hand picking, control may be achieved by spraying with pesticides. Spraying at dusk is likely to be more effective
- Organic contact insecticides containing natural pyrethrum (e.g. Bug Clear Ultra 2, Neudorff Bug Free Bug and Larvae Killer). Several applications of this short persistence products may be necessary to give good control
- More persistent contact-action insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer, Provanto Sprayday Greenfly Killer) and cypermethrin (e.g. Py Bug Killer)
- A systemic containing the active ingredient Flupyradifurone (Provanto Smart Bug Killer) is available for use on ornamentals and selected edibles
- The systemic neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra) is also available
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.
Pesticides for gardeners (pdf document outlining pesticides available to home gardeners)
The larvae of geum sawflies (Claremontia waldheimii and Monophadnoides rubi) feed on the foliage of cultivated and wild Geum species.
There is one generation a year with larvae active during late May and June. They initially feed concealed between the folds of unexpanded leaves. The larvae of both species are pale green with rows of bifurcated (divided into two) whitish spines on the dorsal surface. When fully grown in late June they go into the soil where they spin silk cocoons, where they overwinter. The adults are 5-6mm in length, black in colour and emerge between late April and early June.
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