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Hort Update for March 23, 2018

Kermes Oak Scale, Nebraska Extension Hort Update for March 23, 2018, http://communityenvironment.unl/update03232018
Image by Jim Kalisch, University of Nebraska - Lincoln Insect Diagnostician
Serious ConcernsMajor Symptom:
1. Kermes 0ak scale Twig and branch dieback in oaks; pale brown hemispherical, tough, gall-like scales present
Minor IssuesMajor Symptom:
2. Spruce spider mite Early season mite, injures foliage of spruce, arborvitae, juniper, hemlock, pine, Douglas fir and other conifers
3. Black vine weevil larvae Root and crown feeding of mature grubs in spring causes wilting and death of preferred hosts, including yew and rhododendrons
4. Conifer aphid Large grayish aphids found in early spring on juniper, pine, spruce and other conifers
5. Pine bark adelgid White woolly material on trunk and branches; white pine preferred host
Position Announcement
6. Forest Health Specialist, Nebraska Forest Service

The Nebraska Forest Service has an opening for a Forest Health Specialist. The application process is online, and applications should be submitted by April 6, 2018.  The job is posted at:   https://employment.unl.edu/postings/58358

Job Summary Forest Health Specialist with Nebraska Forest Service:  

Provide technical assistance and information to tree care professionals, landowners, homeowners, and local government agency personnel related to the emerald ash borer, thousand cankers disease of walnut and common insect pests and diseases of trees in Nebraska. Conduct workshops and seminars, write publications and newsletters and use other media to present information, diagnose tree pest problems and conduct tree pest surveys.
Professional ResourcesMajor Symptom:
7. Pruning Fruit Trees Free publication. Pruning, maintenance techniques, and timing for fruit trees.
8. Growing Hops

Hops on a Quarter Acre, EC3026

Estimated Costs of Producing Hops in Nebraska, EC3010

Hops Downy Mildew, G2297

Herbicide Weed Management on Hops


1. Kermes oak scaleTwig and branch dieback in oaks; pale brown hemispherical, tough, gall-like scales present

Kermes Oak Scale, Nebraska Extension Hort Update for March 23, 2018, http://communityenvironment.unl/update03232018Image by Jim Kalisch, University of Nebraska - Lincoln Insect Diagnostician

Pale brown, hemispherical scales appear as large growths attached to leaf midribs and twigs. Mature scales are very tough and gall-like. Leaves become stressed, yellow, or withered, and honeydew secretions are evident. Infested trees can suffer serious branch dieback, but infestations are usually isolated to specific trees and are rarely widespread.

This scale produces a profuse amount of honeydew that covers leaves and becomes blackened by sooty mold. Ants and many other insects feed on the honeydew, and there are a number of natural enemies that help restrain populations.

Nebraska records have confirmed the presence of Kermes Scale since 1921. Hosts affected have been red, pin, and bur oaks, but a wide range of oaks can be infested. Counties involved in the records include Gage, Otoe, Richardson, Pawnee, Lancaster, Douglas, Dodge, Saline, Sarpy, Platte, and Buffalo counties, but this pest is undoubtedly widespread across the state wherever oaks occur. 

There is one generation per season, with females reaching maturity in June. Crawlers emerge in September then migrate to buds being formed for the following year where they spend the winter.  A dormant-season spray oil from March through mid-April is an opportunity to treat. Crawlers are also susceptible to control in September with a topical insecticidal spray.

Kermes Oak Scale, Kansas State Research and Extension

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2. Spruce spider miteEarly season mite, injures foliage of spruce, arborvitae, juniper, hemlock, pine, Douglas fir and other conifers

Stippling of needles becomes evident on older foliage in early spring. By early summer, infested portions turn yellow or brown and appear dried out. Dirty, fine webbing is evident. Occasionally heavily infested trees suffer severe damage. 

Monitor regularly for early damage in April. Treat infestations with vigorous sprays of an insecticidal soap or an insecticide/miticide. Thorough coverage is important, and re-treatment is often necessary. By mid summer, infestations naturally decline; do not treat.

Spruce Spider Mite, Penn State University Extension

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3. Black vine weevilRoot and crown feeding of mature grubs in spring causes wilting and death of preferred hosts, including yew and rhododendrons

Larva are active in spring, from early March through the end of May, and again in summer, from late August through late November. Mature larvae are legless, creamy-white, over one-half inch long and have a brown head. Their feeding on roots and in crowns causes wilting, desiccation or death of host plants. Preferred larval hosts include yews, rhododendrons and hemlock.

In spring, first confirm the presence of actively feeding larvae, then drench the soil around host plants with a water-soluble insecticide according to label directions. Parasitic nematodes are practical and effective in moist conditions for single shrubs or potted plants.

Summer damage occurs from adult weevils feeding at night. Needles close to base of plant have numerous notches and feeding scars. Foliage may appear stressed, yellowed or desiccated from larval feeding below ground.

Since adults crawl and cannot fly, pick off adults in the early morning on small host plants. Treat larger plantings in the evening with a persistent or systemic insecticide with thorough coverage, especially toward the base.

Black Vine Weevil, Ohio State University Extension

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4. Conifer aphidLarge grayish aphids found in early spring on Juniper, pine, spruce and other conifers

Large grayish aphids with spots on the body and long legs, present from mid-March through late June and again in fall from mid-September through late November. They feed in terminals, and heavy infestations cause needles to turn yellow and reduce tree growth, especially in young trees. Lady beetles and other natural enemies may be present.

Conifer aphids thrive in the spring and autumn; by summer, colonies decline from attack by natural enemies. Treat heavy infestations with an insecticidal soap, neem oil, or horticultural oil spray. A dormant oil spray controls black eggs that are overwintering on terminal needles.

Giant Conifer Aphids, US Forest Service

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5. Pine bark adelgidWhite woolly material on trunk and branches; white pine preferred host

The trunk is covered with woolly material in which aphids are feeding and reproducing. Insects may be present from early March through late November. White pine is the preferred host. Young trees can become stunted, weakened and die.

Monitor trees for infestations throughout the growing season. Use a dormant oil spray in early spring to smother overwintering aphids hiding in bark crevices. Spray active infestations during the season with an insecticide and enough pressure to penetrate the woolly material.

Pine Bark Adelgid, Penn State University Extension

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6. RoundUpRoot and crown feeding of mature grubs in spring causes wilting and death of preferred hosts, including yew and rhododendrons

Larva are active in spring, from early March through the end of May, and again in summer, from late August through late November. Mature larvae are legless, creamy-white, over one-half inch long and have a brown head. Their feeding on roots and in crowns causes wilting, desiccation or death of host plants. Preferred larval hosts include yews, rhododendrons and hemlock.

In spring, first confirm the presence of actively feeding larvae, then drench the soil around host plants with a water-soluble insecticide according to label directions. Parasitic nematodes are practical and effective in moist conditions for single shrubs or potted plants.

Summer damage occurs from adult weevils feeding at night. Needles close to base of plant have numerous notches and feeding scars. Foliage may appear stressed, yellowed or desiccated from larval feeding below ground.

Since adults crawl and cannot fly, pick off adults in the early morning on small host plants. Treat larger plantings in the evening with a persistent or systemic insecticide with thorough coverage, especially toward the base.

Black Vine Weevil, Ohio State University Extension

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