Holly leaf miner larvae mines out the leaf middle leaving yellow or brown trails. Use Diazinon or Orthene when the mines are first noticed. Scales of various types may infest holly. Crawlers can be controlled with Orthene, Diazinon, or malathion. Two to three sprays may be needed at 7 to 10 day intervals when Orthene is used. The other two chemicals are used when ever the crawlers are present. 
Spider mites cause discoloration and speckling of holly foliage. Use sprays of Orthene.

Diseases

Tar spot may occasionally cause small yellow spots on the leaves in summer. Eventually the spots turn reddish brown with narrow yellow borders. Leaves may not drop prematurely but the infected areas drop out leaving holes in the leaves. Gather up and destroy badly infected leaves. 

Many different fungi cause leaf spots on holly. Reduce the injury caused by leaf spots by keeping trees healthy. Should a leaf spot become serious, identify the causal fungus before spraying. Dispose of diseased leaves. 

Cankers caused by several different fungi lead to sunken areas on stems and plant dieback. Keep trees healthy and prune out infected branches. 

Spine spot is small gray spots with purple margins and is caused by spines of one leaf puncturing an adjacent leaf. 

Chlorosis symptoms are light green or yellowish leaves with darker green veins. This problem is due to a high pH leading to iron deficiency. Use acidifying fertilizers and chemicals to bring down the pH. Sprays of iron chelate will green up plants until the pH can be lowered. 

Hollies scorch during the late winter due to rapid and wide temperature fluctuations. Shade plants during the winter to prevent the problem. 

Purple blotches on the leaves are caused by some environmental factor such as nutrient deficiencies, drought, and winter injury.