Pest and disease Factsheet - Turf pests - Risks posed by leatherjackets and chafer grubs

Soil-dwelling larvae of chafer beetles and crane flies are serious turf pests, feeding unseen in the topsoil layer beneath lawns, golf courses and sports fields.

Chafer grub larvae - image: iStockphoto
Chafer grub larvae - image: iStockphoto

Chafer grubs also feed on roots of young trees, herbaceous perennials and nursery stock. Adults eat the foliage and flowers of some ornamental trees.

The most common chafers are the garden chafer (Phyllopertha horticola), which is the most serious pest on turf, Welsh chafer (Hoplia philanthus), most often found in sandy soils, and summer chafer (Amphimallon solstitialis).

Cockchafer (Melontha melolontha) is most often associated with deciduous woodland and can be a pest on neighbouring nurseries.

Rose chafer (Cetonia aurata) adults damage plants, feeding on rose flowers and foliage. The larvae feed on organic matter, such as dead wood.

In the USA, Japanese beetle (Popillia japonica) is the most destructive member of the chafer family. Larvae attack grass roots and adults damage various ornamental and agricultural plants. It is still a quarantine pest in the EC.

There are two main pest species of crane fly, Tipula paludosa and Tipula oleracea. Larvae, commonly known as leatherjackets, cause significant damage in cereals, amenity grass areas and nursery liner pots.

How to recognise them

Chafer larvae are white to light brown with a brown head and biting mouthparts. They assume a typical C-shape and look similar to vine weevil larvae but have three pairs of brown thoracic legs close to the head - vine weevil larvae are legless.

Welsh chafer is the smallest adult, at 8-11mm long, with a black head, thorax and legs. Garden chafer and summer chafer are similar in size as adults at about 12mm, although some say summer chafer can reach 18mm. Summer chafer is entirely brown and hairy, while Welsh chafer and garden chafer have a metallic blue-green head and thorax. Rose chafer is larger, at up to 20mm long, and metallic green all over.

Cockchafer is the largest chafer beetle, at 25-30mm long as adults and 40mm as larvae. Adults have brown wing cases, white markings on the abdomen and feathered antennae.

Leatherjackets are uniformly grey-brown and wrinkled, with no distinct head. They are legless and their tapered bodies are 4-5cm long when fully grown. Adult crane flies are long-legged and narrow-bodied with one pair of transparent true wings.

Biology

Chafer beetles Adult chafer beetles are active from late spring. After mating, the female lays eggs in soil during early summer. Larvae feed on roots through summer until autumn, overwintering as larvae in cells made further down in the soil. Mature larvae pupate in spring. Some species, such as garden chafer, pupate within the year. Larvae of other species may take several years to develop before pupating. The cockchafer has a three-year life cycle.

Garden chafer adults emerge from the soil within a few days of each other in late May to early June. In badly infested areas, newly emerged male beetles can be seen swarming, looking for females.

Crane flies Adults of Tipula paludosa emerge from pupae from late July to September. Females lay eggs in the soil close to the stem bases of grasses, which hatch into 2mm-long larvae in a couple of weeks. Larvae feed on roots, stem bases and, on damp evenings, basal leaves during autumn and milder winter periods, growing more quickly in spring, when the most damage is done. Infestations are favoured by damp, mild autumns.

Tipula oleracea adults can be found during the spring and summer. Females lay eggs over a longer period and fly further than those of Tipula paludosa.

Symptoms

Grass weakened by chafer larvae thins out, yellows and turns brown in dry weather. Weeds tend to colonise patches where grass has been killed. The larvae can easily be found just under the turf and are targeted by birds, badgers or foxes, which in turn seriously damage the turf as they seek them out.

Badly maintained turf or, on golf courses, well drained sandy soils and less disturbed areas, such as the sides of bunkers, are more susceptible to attack. Injury to saplings results in stunted growth, premature leaf drop and sometimes sudden wilting.

Newly hatched chafer larvae are only damaging if present in high numbers. Damage is at its worst when larvae are fully grown, which is in the autumn in the case of garden chafers.

Young plants attacked by leatherjackets yellow and wilt or can be severed, with symptoms similar to damage caused by cutworms. Damage to lawns resembles that caused by chafer larvae, with yellowing in dry weather and secondary damage caused by birds hunting for leatherjackets.

Severity of damage is related to the pest population and the condition of the sward - stressed, shallow rooted or slow-growing grass is less likely to recover from attacks. Areas that are newly cultivated tend to be worst hit.

Treatment: biological control

Nematode products are available for leatherjackets (Steinernema carpocapsae and Steinernema feltiae) and chafer larvae (Heterorhabditis megidis). To improve results, apply in the evening and irrigate grass or turf before and after application. A minimum of 12 degsC soil temperature is required for effective control and soil must be kept moist for at least two weeks during treatment.

Chafer beetles are a food source for ground beetles and natural populations will help keep pest numbers down.

A fly parasite, Bucentes geniculata, can provide some leatherjacket control in garden and amenity situations. It has been found naturally on a number of sites in southern England.

There are two generations - one in spring and one that overwinters in larvae and feeds on these infected leatherjacket bodies during the cooler months before emerging in the spring.

Treatment: cultural control

Chafers Infestations may be avoided if turf is watered and fed. A heavy rolling in late spring may also reduce adult emergence.

Leatherjackets Larvae favour moist ground so good drainage should restrict pest populations.

Small, high-value areas such as golf greens can leave tarpaulin or cardboard on the ground overnight to bring leatherjackets to the surface, where they can be removed.

Treatment: chemical control

Three active ingredients are approved for use in various situations for the control of leatherjackets or chafer larvae:

1. Chlorpyrifos such as Clayton Pontoon 480EC (Clayton), Cyren (Headland), Equity or Dursban WG (both Dow).

2. Imidacloprid such as Merit Turf (Bayer Environmental) and Clayton Divot (Clayton).

3. Methiocarb such as Decoy Wetex or Draza Forte (both Bayer CropScience). End purchase date of all products 18th September 2014.

Go to www.pesticides.gov.uk for the latest approvals.

Fully updated by Dove Associates.

Use plant protection products safely. Always read the label and product information before use. Dove Associates shall in no event be liable for the loss or damage to any crops or biological control agents caused by the use of products mentioned.


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