Thought these might help:
http://www.syngenta-crop.co.uk/NR/exeres/5D749023-FE95-4C85-9A85-987D4D63E7A8,frameless.htm
http://www.dgsgardening.btinternet.co.uk/wireworm.htm
http://www.organic.aber.ac.uk/library/wireworm%20control%20and%20brassica%20green%20manures.pdf
HDRA Factsheet (available online to members only):
Wireworm
Often troublesome in newly cultivated ground, wireworms are the larvae of various species of click beetle. The two most common are the garden click beetle, Athous haemorrhoidalis and the common click beetle, Agriotes lineatus. Wireworms attack the underground parts of plants, damaging roots, tubers, corms and stems. Favourites are potato, beetroot and carrot as well as corms and tubers of anemone, dahlia, and gladioli. Damage to roots of strawberries, brassicas, beans, tomatoes and many seeds and seedlings can occur where infestations of wireworm are high.
Typical Symptoms
Damage can occur all year but most damage is in spring and autumn. Damage is often most severe on newly cultivated land, but wireworm larvae may remain in the soil for many years before pupating to adults (see life cycle below).
Tubers and root crops: Small, knitting needle sized entry holes 2-3mm across are seen on the outside of the tuber or root. On cutting open, a network of tunnels may be evident, often invaded and enlarged by other pests such as slugs or woodlice. Further bacterial and fungal rots may develop making them unsuitable for storage.
Corms: Similar damage to tubers above.
Seedlings: Stems are bitten through at or below soil level.
Roots and stems: Roots may show small blackened pits where feeding has occurred; plants may suddenly wilt and die. On fleshy stemmed plants such as tomato and chrysanthemum, wireworm may tunnel into the stems and upwards into the pith. On crops such as maize, stems may be chewed and frayed just above the old seed.
Description of the pest
Wireworm larvae are tough skinned, cylindrical, golden yellow to orange brown in colour and reach up to 25mm in length when mature. Three pairs of thin small legs are located behind the head.
Life cycle
The female click beetle lays her eggs just below the soil surface from May to June, favouring grassland and weedy soil. There may be several sessions of egg laying resulting in a patchy infestation throughout the area. A month later the larvae will hatch and feed on both living and dead plant material in the soil for up to five years. The larvae move through the soil profile in response to changes in moisture and temperature. In warm soils (above 10°C) the larvae feed close to the soil surface. Hotter or much colder temperatures cause the larvae to descend deeper, seeking more favourable conditions. This is why most crop damage occurs in the late spring/early summer, and early autumn. Eventually the larvae construct pupal cells at about 20cm depth in the soil, pupate and emerge during the following summer and early autumn to mate.
Prevention and control
Cultural control: Thorough cultivation, before planting and after harvesting will help to expose the wireworm to natural predators such as birds, frogs, hedgehogs and rove beetles. Remove host grass weeds, where the beetle is known to hide.
Check compost heaps: Expose home-made compost and turf stacks to birds and other predators before use, if they are infested with wireworm.
Harvest early: To limit damage to potatoes and other root crops, lift them early if wireworm is known to be present.
Traps: In infested spots in the garden or greenhouse, place a feeding trap. Spike wire through chunks of raw potato or carrot and bury under the soil surface, approximately 10-14cm down. Best done in spring or autumn, check regularly and destroy any wireworm larvae found.
Bury a pot or net of pre-soaked grain. Wheat or corn are especially useful. Soaking the grain, a day in advance to trapping, promotes seed germination and increases the baits’ attractiveness to wireworm. Cold soils (<10°C) can be warmed up by covering with a sheet of black plastic. Dig up regularly and remove the pest.
Green manure: Growing mustard, Sinapsis alba as a winter intercrop is said to speed up the life cycle of wireworm in the soil, reducing population levels especially in new grassland.
Lois
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