Magazine - Chafer Grub - The Organic Solution

By Samantha Cassidy in Consultancy on 27th Aug 2010 8:00

So far, the weather in 2010 has presented many challenges for both greenkeepers and groundsmen - an extremely cold winter, late spring and early summer drought have made the management of high quality turf as challenging as ever!

This year's weather has also had a big impact on the behaviour and potential impact of one of the most damaging turf pests - the Garden Chafer (Phyllopertha horticola).

During the winter the larvae of the garden chafer move deeper into the soil, so they were well adapted to survive this year's prolonged cold and frozen soil conditions. The late spring certainly had an impact on adult emergence, as soil temperatures slowly increased the garden chafer pupae moved closer to the surface and the adult beetles emerged later than normal in early June; anybody who attended Derby Day on Epsom Downs will know this all too well. The Times reported that the main challenges for spectators on the famous Epsom Hill on Derby Day was to negotiate the twin challenges of flying beetles and sun stroke!

This year the adult beetles reproduced in perfect early summer conditions, the early summer drought had already started to impact the turf and, in most of the country, fairways and outfields soon burnt off resulting in thinner turf cover than normal. This provided perfect and easy conditions for the adult females to burrow into the turf and lay their eggs.

So what does this mean to the threat of damage this autumn directly by the root feeding larvae of the garden chafer or by secondary damage from birds and large mammals?

All indications are that there will be higher than normal populations of garden chafer larvae this autumn, and there is a higher potential that they will directly or indirectly cause significant damage to turf surfaces.

Direct feeding by the larvae on turfgrass roots could contribute to poor recovery of already drought damaged turfgrass, and secondary damage could be even more disruptive than normal due to foxes and badgers being able to rip up more the thinner turf than normal in search of larvae.

So what can be done to prevent the damage potential?

Firstly, as with all pest and disease management, good observation is critical

• Check areas where garden chafer larvae have been noted before and assess populations.
• Look for areas of turf that are slower to recover from the recent dry conditions, areas that continue to appear to be suffering from drought stress, these could be areas where larvae are feeding on the roots. A quick inspection below the turf will confirm if garden chafer larvae are present.
• As soon as secondary damage is noted, check the area to see what pest is being searched for, if birds are pecking for larvae, this can be a good indication and it is better to treat the area quickly before potentially more damaging secondary feeding by larger mammals

Secondly, if control measures are required the most effective contact control of garden chafer is by the use of beneficial nematodes. August until the beginning of October, when the grub is actively feeding, is the optimum time for nematode treatment:

• The contact action of this biological control means that the applied insect parasitic nematodes are effective immediately after application.
• Once the nematode comes in contact with the garden chafer larvae, they will enter the larvae and start to feed and reproduce, the garden chafer larvae will stop feeding in 2 - 3 days after infection and will be killed in 2 to 3 weeks following infection.

As with all plant protection product applications, care with application is critical, for the best results adequate soil moisture to the treated area should be maintained after application to ensure nematode survival and the most effective performance from the treatment.

Chafer Lifecycle:

Read more articles in Consultancy, by Samantha Cassidy or from August 2010.

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