Wireworms
What are wireworms and should we be worried about them? Find out, in our guide.
Wireworms are the soil-dwelling larvae of the click beetle, and live predominantly in undisturbed grassland. In gardens they can sometimes cause problems by eating the roots of seedlings and older plants, as well as burrowing into root vegetables. There are around 60 species of click beetle in the UK and only a handful of their larvae cause problems, yet all of them are a source of food source for creatures such as birds and small mammals. In general, wireworms may only be a problem in ground that has been converted from lawn or grassland into a vegetable plot, particularly when root vegetables such as potatoes are grown.
Identifying wireworms
Wireworms are orange brown in colour and have long, narrow, segmented bodies with three pairs of legs behind the head. This gives them a wire-like appearance, hence their name. They are only 1-2cm long and 1-2mm across, so are quite hard to spot in the soil. In the UK wireworms are predominantly active from March to May and September to October. They can live for up to four years.
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Wireworms may eat the roots and tubers of many different plants. The damage caused by wireworms is visible on root vegetable crops, particularly potatoes, where wireworms tunnel into the root and cause brown or black areas. However, wireworms may not be the only culprit as other creatures such as slugs or carrot root fly may have made the initial holes, and the wireworms then enter the root or tuber. If there’s only small amounts of damage, simply cut out and discard these parts when preparing food for cooking, but do not store damaged roots as they will quickly rot. Lifting root crops as soon as they are ready is a good approach, rather than leaving them in the ground, where they are susceptible to attack. Wireworms can cause the collapse and death of seedlings, and can also eat away at the roots of larger plants, causing them to grow with reduced vigour.
How to get rid of wireworms
Plants growing in ground that has recently been brought into cultivation from lawn or grassland are most likely to be at risk, so avoid growing susceptible root crops and seedlings in new ground in the first few years. You can control wireworms naturally by regular cultivation to reduce wireworm populations. The spherical, translucent eggs, 0.5 mm across, are laid in clusters just below the soil surface, so a light hoeing brings them to the surface where they dry out, to be eaten by birds and other wildlife. Encourage birds, hedgehogs and other creatures, which feed on the larvae.
There are no chemical pesticides suitable for gardeners to use to combat wireworms. The best product to kill wireworms is a biological control: the nematode Heterorhabditis bacteriophora. As biological controls are living organisms, applying at the right time and according to instructions is important: generally, between spring and early to mid-autumn, when soil temperatures are between 12 and 20֯C. However, be aware that this control may be unnecessarily killing other harmless soil-dwelling larvae, so only apply if there is a clear problem with wireworms.
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