Question
Hi,my holly bushes have small white grub like infection on the underside of the leaves,and on the stems,the hedge is 6years old and we had three die this year in different area's,I have sprayed with a general pesticide but 2 months later they are still spreading.many thanks John

Answer
Sounds like leaf miners.
Leafminers: Leafminers (Phytomyza species) are common pests of hollies. In South Carolina, the native holly leafminer (Phytomyza ilicicola) is the most common. Leafminers are the larvae (immature forms) of small (about 1/8-inch in length) black and gray flies. The larvae are about 1/16 inch long. The adult female inserts eggs into young leaves through puncture wounds made by her ovipositor. The presence of many punctures can result in deformed leaves. The eggs hatch in about four days. The larvae then tunnel through the leaf between the upper and lower surfaces. The paths they follow turn yellowish brown and typically broaden into a blotch. Their presence inside the leaf protects them from many insecticides. Parasitic wasps and birds are natural predators of these pests. American holly (I. opaca) cultivars are particularly susceptible to leafminer damage.

Control: With a light infestation, homeowners can handpick and destroy infested leaves. Foliar insecticides labeled for use by the homeowner include systemic insecticides, such as acephate (Ortho Japanese Beetle Killer) for larvae in mines in May. As an alternative, imidacloprid (Bayer Advanced Garden Tree & Shrub Insect Control Concentrate) as a soil drench systemic insecticide is effective in controlling the larvae within the leaves. Treat shrubs with imidacloprid in the early spring for season-long protection. Read and follow all label instructions and precautions.