Monday, June 17, 2013

Pest News for Week of June 17th


From: Steve Frank, Extension Entomologist

Fungus Gnat Larvae

This week we had reports of fungus gnats forming long lines on sidewalks and driveways. This happens after a lot of rain or heavy irrigation. In the landscape larvae feed on plant roots and live in areas with a lot of thatch or organic matter. You can read more and see a picture of the larvae-snake in an insect note at

Tea Scale Crawlers are Active

Tea scale, Fiorinia theae, is common on camellias. It is an armored scale that lives on the underside of leaves. You can find it on almost any camellia by looking for inner leaves that have yellow spots on top. When you turn it over you will see tan canoe-shaped scale covers and some white fluff from the males. These are tough to treat because the heaviest infestations are often deep within the foliage of large bushes. To find an insect note with more information and recommendations:

Cottony Cushion Scale Activity

Cottony cushion scale, Icerya purchasi, is active much of the year. This week I found young crawlers that were being aggressively tended by fire ants on cherry laurel. The scale is most easily recognized by its oblong cottony ovisac that can reach 1 cm or longer. The rest of its lifecycle is less conspicuous though it is still one of the larger scales. Like other cottony scales, such as cottony maple scale and cottony camellia scale, cottony cushion scale is a soft scale. In the coming weeks the scale will be most easily managed as crawlers are active and exposed. Horticultural oil can be used to smother crawlers on small plants. A systemic drench can be used to treat larger plants and provide longer protection. The host list for this species is long and varied including: maple, boxwood, pecan, cedar, citrus, apple, Prunus spp., rose, and others. This week I found ovisacs on Euonymus, Nandina, and Fatsia. More information and chemical recommendations can be found in the cottony cushion scale insect note at

Spider Mite Damage

Although the cool season is over, damage from cool season mites is beginning 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.
I found all stages of southern red mites on cherry laurel, but they feed on many broadleaf evergreens such as azalea, camellia, holly, and rhododendron. With eggs juveniles and adults all present these mite populations are well underway and deserve attention from nursery and landscape personnel.

Scout plants that had mites or mite damage the previous year 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.  

For more information and control options consult the North Carolina State University insect note at

For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.