Sorry it is taking you so long to get an answer Dennis but these nasty click beetle larvae are rather difficult to control. The first thing is good garden hygiene that is keep the soil clean of weeds and dead plants then a 'possible' organic answer is to use a garlic spray.

Blend 100 grams of grated and crushed garlic cloves, 0.5 litres of water and 10 grams of soap (Use potash based soft soap that is used for washing dishes and not the modern washing powders that contain caustic soda which will harm plants). Mix well. Strain the mixture through a fine cloth. Dilute the solution in 5 litres of water. How to use: Mix the solution well before applying to the affected plants. Use as a spray or sprinkle using twigs or grass tied together to form a whisk. For best effect, use the mixture immediately.

Years ago, my late father got a real infestation and had to soak the ground with Jeyes fluid to get rid but you should note that not only is Jeyes an insecticide but is also a herbicide and it has been illegal to use it for this purpose for some years.