Although the cool season is over, damage from cool season mites is beginnig to appear. I
found this cherry laurel with extensive mite stippling. On the leaves there were no active mites just lots of eggs. This is the last stand of southern red mite for the summer. They spend the hot months as eggs then come out again in fall. They feed in spring but often the damage does not become apparent until the plants face some stress in hot weather. So be sure to monitor these plants in fall. Horticultural oil may help smother the eggs but be careful in hot weather.
In North Carolina, the most important cool season mites are the spruce spider mite (Oligonychus ununguis) and southern red mite (Oligonychus ilicis). These are among the earliest and most damaging pests in nurseries and landscapes. As their name implies, cool season mites are active in spring and fall when they suck fluid from cells on plant leaves and needles. In hot summer months these mites are dormant. However, it is summer when their damage becomes apparent as chlorophyll bearing cells die. Thus, by the time plants exhibit aesthetic damage the mites are gone and treatment is wasted.
Scout plants that had mites or mite damage the previous year as they are likely to have them again because the mites have overwintered as eggs. You can identify plants that had mite last year by looking for fine stippling damage on the old leaves. Turn them over and look with a hand lens for silk webbing, shed skins, and mites. On broadleaf evergreens, look on the underside of leaves for the southern red mite. The most efficient method of scouting for cool season mites (and other mites) is to hold a piece of white paper or a paper plate below a branch and strike it with a pencil or stick to dislodge arthropods. Spider mites will appear as tiny moving specks about the size of the period at the end of this sentence.
Read our recent article about spider mites
from Nursery Management. For more information and control options consult the NCSU Insect Note.