2 Pests: The Chafer Grub

Pests: The Chafer Grub

By Laurence Gale MSc


What is a pest? By definition a pest is a living organism that negatively impacts on agriculture/sports turf operations and/or wildlife habitats. This includes plants, noxious weeds, insects, diseases, birds, animals and rodents, in fact anything that affects the performance and well being of natural turf is considered a pest by groundsman. This may also include the actions of fellow human beings who sometimes accidentally damage the turf whilst carrying out maintenance operations.

However, in general, the term 'pests' relates to insects, birds and mammals.

Problems occur when there is an inbalance in nature and these pests become dominant in a given environment. Luckily, for us in the UK, turf grass pests are indeed very few. However, what pests we do have can cause considerable damage to turf by the impact and relationship these pests have with one another, usually influenced by the feeding chain of these species.

For example, the chafer beetle in its adult form does not cause much damage in turfgrass situations. It is when this insect is in the larvae stage of its life cycle that it becomes a problem. The larvae remains in the ground at a depth of around 80-150mm and feeds on the root tissue of plants. Large infestations can destroy large areas of turf. The problem is compounded when mammals and birds begin feeding on the larvae resulting in heavy surface damage.

In the coming weeks we will feature and identify a number of turf pests, detailing their life cycle, activities and ways you can control them.

Understanding the life cycle and feeding habits of pests will help you reduce the impact and damage that can result from their activities.

This week's Pest is: The chafer grub (Phyllopertha horticola)

Scientific name

Common Name

Life cycle

Phyllopertha horticola

Garden Chafer grub

One year life cycle (egg , larvae, pupae , adult)

Introduction

Chafer grubs can cause serious amounts of damage, particularly in fine turf situations such as golf greens, tees, fairways and bowling greens.

During the larvae stage,the grub is actively feeding on plant root tissues. The severity of the feeding will and can result in turf decline or death.

Damage can be devastating especially when predators of the chafer grub, namely badgers and birds, are feeding. In their quest to find the grubs they end up digging and damaging the turf surfaces.

Eggs

As soon as the female has mated (June time) she will re-enter the ground to lay her eggs. The eggs are laid in groups of 2-6, with a total between 10-50 eggs laid 10cm below the soil surface.

The eggs hatch out four to five weeks later into larvae.

Larvae

Over the autumn and winter the larvae feed on root tissue below the ground. During this time they will go through three instars (growing stages) getting bigger at each stage. The third and final instar sees the larvae prepare itself for hibernation in March. The larvae can grow up to 1.8cm long. No feeding takes place between hibernation and pupation.

Pupae

Pupation of the chafer beetle is usually in May, and after four weeks the adult beetles will begin to emerge.

Adult

Adult beetles are about 9mm long with brown wing cases and a green head. The adult beetles emerge and are seen in June, however, this will be dependant on air temperatures. Adults generally emerge over a period ten days. Male adults may swarm during sunny conditions whilst looking for emerging females.

Females mate as soon as they emerge and then burrow back into the soil to lay eggs. Once the female has laid her batch of eggs, she will re-emerge from the ground, feed herself and then lay another clutch of eggs.

Adult chafers eat the leaves and flowers of many deciduous trees, plants and shrubs, but rarely cause any serious damage in the UK.

Habitat

The beetles require grassland, amenity and sportsturf on a sandy/loam and free draining soil environment to lay their eggs and for the larvae to feed.

Symptoms

The damage to the grass is seen as patches of dead and dying grass coupled with yellowing of the turf especially during dry periods. Where there has been severe infestations of grubs the sward will be weakened to such an extent that the turf can easily be damaged by wear and tear from play or feeding birds and animals.

Most turf damage is caused by other creatures that feed on the grubs. Moles, badgers and birds are the main predators. A badger can do severe damage to any area that is infested with the grubs.

Cultural Control

Good cultural practices will increase the sward's ability to overcome damage from root loss. A strong, healthy plant is able to recover quickly and develop new rooting structures to compensate for any damage caused during the feeding.

Chemical Control

Chemical control is available but its efficiency can be compromised by many factors:-

  • The timing of applications.

  • The choice of chemicals available.

  • The condition of the soil.

  • Severity of the infestation and instar stage.

  • Depth of the grubs.

Use pesticides as a last resort, but when you do ensure you use and apply in accordance to the manufacturer's instructions and at the correct dosage. Applying inappropriate doses will lead to the pest becoming resistant to the active ingredients of the pesticide.

The choice of chemicals for controlling chafer grubs is limited. Many of the most effective ones have been taken off the market. We are now are left with a number of products that are designed for other pests, namely, leather jackets and fruit fly but, in the right conditions, have been successful in controlling chafer grubs. The active ingredients used in most formulations available are chlorpyrifos and thiophanate-methyl.

Current products available:-

For a list of current products availble contact a BASIS pesticide advisor 01902 440250.

The long awaited launch of the new chafer grub control product from Bayer Environmental Science was confirmed at BTME 2005. Although the name has not yet been announced, the product will be available in April 2005. The product is a granular formulation, making it more environmentally friendly than spraying applications and can be mixed with top dressings or sand to employ a preventative control programme.

Ensure you follow manufacturer's directions, health & safety and product data sheets, and comply with COSHH regulations when using chemicals.

Pesticides are an effective tool where high quality turf is desired. However, they must be applied with care and accuracy and in the context of a good overall turf management programme. Before using any pesticide, carefully view the label for conditions of use including rates, methods of application and precautions.

Be careful not to pollute water courses or endanger other wildlife when using pesticides, only use on its intended target.

Other controls

Other methods have been used to control Chafer grubs in the form of bacteria and other organisms such as Nematodes.

Although not all that easy, try and prevent mammals and birds from feeding. Methods may be influenced by the fact that the bird or mammal is protected under legislation, badgers for example. You need to seek advice on how to deal with badger activity.

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