The following is information on foliar nematodes in perennials. Be on the look for this pest in the last weeks of summer.
Foliar nematode injury will increase as perennial foliage ages and we get more leaf wetness from dew and rain. Be on the lookout for symptoms of this nematode pest causing premature dying of foliage in the garden. It is easily overlooked or misidentified. The main symptoms are the angular spots on the leaves limited by the vein pattern of the leaf. The wet weather will be getting aids in movement of the nematodes over the leaf surfaces since they swim in a film of water then enter the leaves through stomata. The host range is very large including popular plants such as hosta, peony, anemonies, ferns, bugbane, plumbago, and many others. Remove infected leaves and destroy them. We still do not have any effective chemical controls for the home or commercial landscape.
Information from Bob Mulrooney, Extension Plant Pathologist, UD