Asparagus beetle adults and larvae feed on the stems and foliage asparagus during the summer months. Extensive defoliation can weaken plants and result in a poor crop in the following spring.
Scientific name Crioceris asparagi
Plants affected Vegetable asparagus, but not ornamental Asparagus species
Main symptoms Presence of adult beetles and grubs. Foliage is eaten and may dry up and turn brown
Most active May-September
What is asparagus beetle?
Asparagus beetle is one of about 250 species of leaf beetle (family Chrysomelidae) found in Britain, they range in size from 1 mm to 18 mm. The family contains many metallic and attractive species and all feed on plants (herbivores).
Both the colourful adult and grey larval stages of asparagus beetle eat the foliage of asparagus, they can also gnaw bark from stems, causing growth above the point of damage to dry up.
- The adult beetles are 6-8mm long (about 1/4in), they are black with six yellow blotches on their wing cases and a reddish thorax
- They can fly and so can reinvade asparagus patches from nearby and from places where it has overwintered
- The adult beetles and their grubs feed on asparagus foliage and bark
- If the bark around the stem circumference has been completely removed, the stem and foliage above dries out and turns yellow brown
Check asparagus frequently from spring onwards so action can be taken before a damaging population has developed.When choosing control options you can minimise harm to non-target animals by using the methods in the non-pesticide section below. Pesticide treatments are likely to kill natural enemies and are only likely to be successful if the entire plant can be reached.
- Small populations are unlikely to affect cropping in subsequent years and can be tolerated
- Hand pick the beetles and larvae from plants when seen from late spring onwards
- Disposing of old stems at the end of the year may destroy some overwintering beetles
- Encourage wildlife in the garden, many animals including birds, frogs and predatory insects such as ground beetles and social wasps will eat the larvae and sometimes adult beetles.
- A biological control is available for asparagus beetle, which contain the nematode Steinernema carpocapsae, suppliers of which can be found in a list of Biological control suppliers.
PesticidesThe RHS recommends that you don't use pesticides. Most pesticides (including organic types) reduce biodiversity, including natural enemies, impact soil health and have wider adverse environmental effects.
Where you cannot tolerate asparagus beetles, manage them using the information above as your first course of action.
Pesticide treatments are likely to kill natural enemies and so reduce the likelihood of natural control and can lead to resurgence of the target animal.
The shorter persistence products (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife.
The pesticides listed are legally available in the UK. This information is provided to avoid misuse of legal products and the use of unauthorised and untested products, which potentially has more serious consequences for the environment and wildlife than when products are used legally.
Always follow the instructions on the products. For edible plants, make sure the food plant is listed on the label and follow instructions on maximum number of applications, spray interval and harvest interval.
Homemade products are not recommended as they are unregulated and usually untested.
Be aware that products such as Neem are not registered for use in the UK and we cannot advise they are used.
- Large plantings, where hand removal is not feasible, can be sprayed with organic contact insecticides containing natural pyrethrins (e.g. Bug Clear Ultra 2, Neudorff Bug Free Bug and Larvae Killer). These pesticides although broad spectrum have a very short persistence and so may require reapplication to keep beetle numbers in check.
- No synthetic insecticides are available to the home gardener for use on asparagus
- Plants in flower should not be sprayed to avoid harming bees and other 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
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
- Asparagus beetles overwinter as adults in sheltered places such as grass tussocks or piles of vegetation. They emerge in May and June and lay elongate black eggs that are attached by one end to the asparagus spears and foliage
- The adult beetles can fly and are very adept at locating patches of asparagus
- The creamy greyish-black larvae reach up to 10mm long (3/8in) when fully grown
- They pupate in the soil
- There are two generations between May and September
- In the autumn, adult beetles seek sheltered places where they overwinter
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