Lawn eating Chafer Grubs

Last September on inspecting a dry patch of lawn. I found an infestation of chafer bugs. I could just roll up my turf, like a carpet, the bugs had eaten all the roots. I removed a large area of turf and revealed just hundreds of the bugs. I dug over the area and removed as many of the bugs, as seen. I treated the area with Provado lawn grub killer, and again in June after seeing just hundreds of the the chafer beetles. I collected and destroyed all beetles seen. I see, on my lawn, an area of small blow holes and small piles of soil, with a hole in the centre, can you identify these ?
 
I am interested in nematodes, would you please advice me when is the best time to apply, or any alternative treatment?
 
Regards

Margaret Grainger 

We are approaching the time when you can apply nematodes for the control of Chafer grubs. They are normally applied late July - Sept. The Chafer grubs need to be in the lawn i.e just under the grass surface. You need to ensure the lawn is moist and water it afterwards for a number of days. This ensures that the nematodes can move through the soil to infect and kill the chafer grubs. You will most likely have to do the treatment each year for a few years until the local population is reduced. Harrod sell the product as Nemasys Chafer Grub Killer. I hope this helps.

Regards

Julian