HELP...my hardy geraniums ....normally trouble free, are under severe attack from a tiny caterpillar which I do not recognise. It's about 1 cm. long .....sort of greyish and very skinny and although very difficult to spot,( because so tiny ,so few of them and they tend to curl up ) they are decimating the leaves of some of my hardy geraniums , which are now beginning to look like filigree / lace work. They are eating tiny but plentiful holes in leaves and seem to be starting at ground level and working upwards....have not yet reached new soft growth.....but it won't be long now!!! How do I control them ?.... they are so tiny and elusive that picking them off is not an option. Would prefer an organic solution if possible since I do not want to affect beneficial insects if it can possibly be helped. Urgent suggestions needed please!!