Sunday, April 21, 2013

Pest News Alert for Week of April 21


From: Steve Frank, Extension Entomologist

Rose Aphids

This week I found a lot of aphids on some rose bushes near my house in Raleigh. I have not yet determined whether they are rose aphids, Macrosiphum rosae, but it doesn't matter a lot to folks managing them. This seems early to have such a large population of aphids but there they are. Aphids can be managed with horticultural soaps or oils or with a number of different insecticides in the aphid fact sheet. One of the most common is imidacloprid but research shows that systemic neonicotinoids like imidacloprid can be harmful to pollinators that ingest pollen and nectar. So consider other options before drenching plants with these insecticides.

Oak Eriococcin Scale Active

Oak Eriococcin, Acanthococcus quercus, is not very well known. Not much research has gone into understanding its biology or control. It is in the family Eriococcidae which includes several felt scales including Azalea bark scale. This scale is quite common around Raleigh and is very apparent this time of year. As the name implies its primary hosts are oak trees. I find it primarily on willow oaks along streets. The oaks on Hillsborough Street (near North Carolina State University campus) are literally covered top to bottom. The scale produce cottony white egg masses that are often in the crotches of twigs. Very little efficacy data is available but there are reports that imidacloprid and other treatments for soft scale work for these as well. Even horticultural oil may be an effective treatment this time of year right after egg hatch. More information can be found at

Cankerworm Update

I have written about cankerworms already, but this year has been bad and I am getting a lot of calls and e-mails about them. At this point, you can expect the cankerworms to hang around for another week or two then disappear. They have defoliated some trees on campus and covered others with dense webbing. Cankerworms do not create webbed nests the way tent caterpillars and webworms do. The webbing is just a tangle of thousands of threads from which the caterpillars dangle. Above are pictures to assist pest managers or Extension agents with calls or complaints so you can see what folks are experiencing.

More information can be found at

From: Emma Lookabaugh, Plant Disease and Insect Clinic, and Barbara Shew, Extension Plant Pathologist

Be on the Lookout for Cedar Apple Rust

Most of us who live in the triangle are hoping for rains to wash away the yellow film of pollen coating our cars, houses, and sidewalks. Spring rains also jump start the most bizarre life-stage of cedar apple rust, a common disease that affects apple trees (and crab apples) and eastern red cedar trees.

The cedar apple rust pathogen (Gymnosporangium juniperi-virginianae) requires two hosts and four spore stages to complete its complex life cycle. On cedar trees, the most obvious signs of infection are firm brown galls, which are about the size of a golf ball and are usually found scattered on the tree’s branches and twigs. After a heavy rain, the galls produce striking bright orange gelatinous horns, which are composed of millions of spores called teliospores. In dry periods, the horns can be seen as short spikes covering the galls. If you find a gall with dried horns, cut it out of the tree, place it in a glass of water and watch over the next few hours as the horns expand.
The cycle of wetting and drying can continue several times during the spring, and in each cycle the teliospores germinate and give rise to another spore type, called basidiospores. These basidiospores are forcibly discharged into the air and are wind-blown to nearby apple trees.

Apple leaves and fruit are most likely to be infected when they are wet and temperatures range from 46 to 75° F. Yellow to orange spots are produced on the upper surface of the apple leaves one to two weeks after infection. The spots on leaves may be raised or swollen and infected fruit may be slightly distorted. Small black dots within the lesions signal the production of the next spore type, the pycniospores (also called spermatia). One to two months later, fringed cup-shaped structures (aecia) appear on the underside of the apple leaves and these contain aeciospores, yet another spore type.

The aeciospores are windblown to cedar trees in late summer to early fall, where they germinate and infect to produce galls. The galls produce teliospores in the second year after infection, completing the life cycle. G. juniperi-virginianae survives in the gall tissue for only two years. After its second year, the spore producing year, the pathogen dies in the gall tissue. On apples, the pathogen survives only a few months, just long enough to produce the aeciospores that infect cedar trees.
Cedar apple rust causes only minor damage to cedar trees from twig dieback. Damage to apple is more significant and can result severe defoliation and fruit blemishes. Since this pathogen requires both hosts to complete its life cycle, control can be achieved by eliminating one host from the surrounding area, although oftentimes eradication is not feasible or desirable. Additional control measures include the use of disease-resistant apple cultivars, properly timed fungicide applications on apple, and removal of cedar galls before spring rains.

Check out this cool video of telial horns expanding (Video: Arlene Mendoza-Moran):

Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina State University, North Carolina A&T State University or North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact an agent of North Carolina Cooperative Extension.

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