Question
My question is I placed mounts of horse manure on the edges of my crape myrtles and found some grub worms and after doing research on line I'm wandering what to put on my trees and grass to kill the grub bugs.... so that the grub worms hopefully die... can you help me?

Answer
All lawns have a low population of white grubs but usually the numbers are low and do not damage the lawn. White grubs (grubworms or simply, grubs) are the C-shaped larvae of a large group of beetles called scarabs. Many species of scarabs are found in the United States and several of these attack turfgrasses. The most important species are: Japanese beetle, Popillia japonica Newman; May or June beetles, Phyllophaga spp.; northern and southern masked chafers, Cyclocephala spp.; and black turfgrass ataenius, Ataenius spretulus (Haldeman). Other, more localized, white grub pests are: European chafer, Rhizotrogus majalis (Razoumowsky); the Asiatic garden beetle, Maladera castanea (Arrow); and the green June beetle, Cotinis nitida (Linnaeus).

Since white grub occurrence is rather sporadic, applying pesticides for control of anticipated grub populations is not recommended. However, in areas where adult activity has been observed or perennial infestations have occurred, preventive applications may be warranted. Currently, imidacloprid (=Merit), isofenphos (=Oftanol) and isazophos (=Triumph) are the only registered products which seem to have extended activity. In field trials, imidacloprid and isofenphos generally perform best when applied before mid-August, or when white grub egg laying is underway.