Dealing with Chafer Grubs
There are two main species of Chafer Grub that cause problems in turf and sports surfaces:
- Garden Chafer Grub (Phyllopertha horticola)
- Cock Chafer Grub (Melolontha melolontha)
The ones shown to the right are the garden Chafer which is much smaller than the Cock Chafer with the larvae growing to 15mm in length.
These will generally last for one season in the soil whereas the much larger Cock Chafer will last up to three years growing to quite a size (up to 30mm in length).
The adults are metallic green and bronze and appear in the spring, generally from May and they will lay eggs in the soil through May and June. The pupae hatch and feed just under the surface on grass roots until the autumn when they tend to burrow into the soil to escape the cold.
Later in the season, the damage is very easy to spot especially in dry weather as the grass suffers from moisture loss due to a lack of roots. In effect, the Chafer Grub detaches the grass from the soil so that it can rolled up like turf.
The bigger issue damage wise is when these juicy grubs are discovered by bird and worse, badgers. Both of these will cause significant damage to a lawn in their efforts to dig up the grubs.
Generally, this occurs in the latter part of the autumn or early spring when the animals are hungry. The picture to the left shows damage caused by birds.
Later in season, the grubs will pupate and emerge as adults in late spring to begin the cycle again.
Historically, we had a substantial range of insecticides which we could use to control this pest, however; over recent years, these have all been withdrawn, mainly as it was suspected that there was a perceived risk to bees and as there is global concern over the decline in bee numbers, these active ingredients have been withdrawn across Europe for the whole of agriculture, amenity and horticulture.
There is a significant amount of work being undertaken to develop new actives, but at the moment we are reliant on biological control in the form of nematodes. These are microscopic worms that naturally occur in the soil and they parasitise the grub by laying their eggs inside them which kills the grub.
They are now very commonly used in food production and do work if they are used correctly. We have to understand that they need good soil conditions to survive in large numbers long enough to be able to find and colonise the host. This means that they need to be applied at the right time and also correctly. After application, they will need to be watered in and the soil kept moist for more than just a day or two. Letting the soil dry completed a few days after application will mean that all the effort has been wasted.
We at Perfect Ground Solutions are more than happy to talk you through the timings and methodology and supply and apply the nematodes for you.
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