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Volume 11, No. 2 April 16, 2004

Contents...

Scouting Report—Conifers (As Christmas & Landscape Trees): Balsam Twig Aphid, European Pine Sawfly, Pine Bark Adelgid, Western Conifer Seed Bug 

Conifers (As Landscape Ornamentals Only)—Fletcher Scale, Gymnosporangium Rusts, Taxus Mealybug 

Broad-leaved Trees and Shrubs: Boxwood Leafminer, Honeysuckle Aphid, Magnolia Scale

Things to Look For—Aphids, Douglas-fir Budbreak, European Pine Shoot Moth, Gypsy Moth, Hemlock Woolly Adelgid, Hickory Leaf Stem Gall Phylloxera, Larch Casebearer, Maple Bladdergall Mite, Nantucket Pine Tip Moth, Zimmerman Pine Moth

Feature Article—Douglas-fir Needlecasts

Growing Degree Days

Phenology

Book Shelf—Recommended Urban Trees

Please Note: Where a specific product is listed after a recommended pesticide, only that product is labeled for that use. Not all products listed are labeled for all uses, so be certain you are getting the right formulation (with the use(s) you want), before you purchase the pesticide.

Note:This information is valid for New York. It may or may not apply in your area.

The Scouting Reports list chemicals registered for control of specific pests. Our recommendations are taken from the 2004 Pest Management Guide  for Commercial Production and Maintenance of Trees and Shrubs. These recommendations apply to New York State.

The recommendations given in Branching Out  are not a substitute for pesticide labeling. Read and follow the label before applying any pesticide!

Scouting Report

Conifers (Christmas & Landscape Trees)

Balsam Twig Aphid (33)—Extremely tiny, pale green, newly-hatched balsam twig aphids were seen on balsam and Fraser fir during our scouting trip to Orange County. White fir (Abies concolor) is also reported to be a host, but we see the pest far less often on it. Looking for tiny droplets of honeydew exuded by the aphids is the easiest way to locate these insects now.

If you are planting true fir this spring, look the stock over carefully before installation. Symptoms of last year's damage will appear as twisted 2003 needles and, perhaps, sooty mold.  Avoiding pest problems by not introducing them in the first place is still a valid pest management strategy.

Where the insect already occurs on established plants, and where budbreak has not yet begun, you should still be able to apply a dormant oil treatment.  If however, budbreak has begun, you should choose one of the other registered pesticides. They should be applied late April to early May (30-100 GDD50). If you do spray after budbreak read the label carefully and observe all precautions about applying pesticides to tender fir growth.

Link to an INFORMATIVE WEBSITE regarding Balsam Twig Aphid-found on the web at the Christmas Tree IPM Pest web page sponsored by the Department of Plant Pathology at Cornell University.There are several good photos on this site.

Link to another INFORMATIVE WEBSITE regarding Balsam Twig Aphid placed on the web by Bugwood.com. There are several good photos.

Link to an INFORMATIVE WEBSITE entitled Balsam twig aphid vs balsam woolly adelgid. Which is it?- placed on the web by Penn State. (This is a PDF File)> There are several good photos

European Pine Sawfly (2)—The eggs of this sawfly were just beginning to swell on our most recent scouting trip. We expect the larvae to emerge soon. This insect is an important pest of red, Scots, Japanese red, jack, Swiss mountain, and mugo pines. The newly hatched sawflies are less than 2 mm long, and each one is grayish green with white markings and a black head. 

Link to an INFORMATIVE WEBSITE regarding European Pine Sawfly-placed on the web by Ohio State University Extension.There are very good photos on this site.

Pine Bark Adelgid (31)—Pine bark adelgids, covered by cottony masses, were seen on white pine in several sites around the state.  They are beginning to lay their eggs, and the crawlers will be soon be active.  It should be noted that the alternate hosts of this pest are species of spruce. Therefore, you may find the insect attacking these trees, too. They can be found on the bark and at the bases of needles of new shoots.  

 Where infestations are light the insects can be removed with a high pressure spray of water.  If infested trees are in stressful sites or are otherwise not particularly thrifty, you may have to resort to application of an insecticide. Horticultural oil can be applied in mid to late April (22-58 GDD50).  Horticultural oil, insecticidal soap or other registered pesticide may be applied from 56 to 618 GDD50 to kill the crawlers.
Link to an INFORMATIVE WEBSITE regarding Pine Bark Adelgid placed on the web by Ohio State University Extension.There are very good photos on this site.


Link to an INFORMATIVE WEBSITE regarding Pine Bark Adelgid placed on the web by the Center for Integrated Pest Management, North Carolina State University .There are very good drawings on this site.

Western Conifer Seed Bug—These recently introduced bugs feed on developing cones of Douglas-fir, pine, and spruces.  The adults are brown, 3/4 inch in length.  They can be a considerable nuisance indoors, not only because they seem to crawl everywhere but also because crushing them releases a strong, vanilla-like odor that offends many people.  In the spring the bugs move out of doors to coniferous trees nearby.  There is not much to do to prevent infestations of these insects in houses except to remove them - carefully - so as not to break the exoskeletons and release the odor.

Link to an INFORMATIVE WEBSITE regarding Western conifer seed bug placed on the web by Penn State Cooperative Extension.There is a good photo on this site.

 

Conifers ( Landscape Ornamentals Only)

Fletcher Scale (42)—Oval, flat, yellowish immatures are overwintering on twigs and needles.  This native soft scale prefers arborvitae and yew and has been reported on juniper and pachysandra.  Heavy infestations will produce honeydew that will, in turn, cause sooty mold.  Needles yellow and may drop prematurely.  Because there are several effective natural parasites, we suggest you use a dormant treatment (38-148 GDD50) of horticultural oil to minimize damage to the parasite population. Link to an INFORMATIVE WEBSITE regarding Fletcher Scale placed on the web by Penn State Entomology

Gymnosporangium Rusts (118,119)—Galls on Juniperus sp. are just beginning to send out "horns". These masses are reddish to golden brown and found attached to twigs.  Within a couple of weeks, depending on the weather, gelatinous tendrils, up to an inch long and ranging in color from reddish brown to bright orange will become very conspicuous as they mature and begin to cast spores.  That will be the time to protect the alternate hosts from infection.

If practical, the galls should be removed from the affected areas in the spring.  Another alternative is spraying crabapple with chlorothalonil, mancozeb, Bayleton, or Zyban. 

These sprays should be applied to crabapple when orange rust masses begin to develop on juniper, around mid-May. They should be applied three times at ten day intervals.  Another alternative is to apply propiconazole at 7-day intervals when rust masses begin to appear on crabapple.

In the future, try to avoid planting junipers and eastern red cedar near hawthorn, flowering crab, quince or similar plants to avoid contact between diseased and healthy plants. In addition, several apple-cedar rust resistant varieties of juniper are now available and can be used to avoid this disease.Link to an INFORMATIVE WEBSITE regarding Cedar Rusts Diseases placed on the web by Ohio State University Extension. There are several good photos on this site.

Taxus Mealybug (37)—The immatures are overwintering in bark crevices of Taxus (yew), beneath old, dirty white cottony ovisacs.  The immatures are less than 1/8 inch long, oval, and covered in a white wax. This pest can also been found on Prunus spp., rhododendron, dogwood, and maple, usually in small populations.  They will mature to adults from June through August, and the females will give birth to live young during early summer. If there is a severe infestations, thin, sparse foliage is seen.  The needles may be caked with honeydew and black sooty mold.

Treat the affected plants with oil for a dormant spray (7-91 GDD50). Spray again with a registered pesticide in mid-May through early June (246-618 GDD50).

Link to an INFORMATIVE WEBSITE regarding Taxus Mealybug placed on the web by Kentucky Cooperative Extension

Broad-leaved Trees and Shrubs

Boxwood Leafminer (94)—The lemon yellow larvae and pupae of this leafminer can be found inside last year's leaves.  These leaves are mined or blistered.  Scout now to see if management will be needed this spring. If deemed necessary a treatment should be made to the undersides of the foliage in the first two weeks of June (448-700 GDD50) to treat the adults.

Link to an informative web page regarding Boxwood Leafminer placed on the web by North Carolina. There are some good drawings on the site.

Link to another photo of Boxwood Leafminer. This placed on the web by Ohio State University Extension.

Honeysuckle Aphid (149)—The new growth is just beginning on honeysuckle and we expect to see these aphids hatching soon. The feeding from this aphid results in witches' brooms on the terminals of honeysuckle leaves. The leaves in these brooms are light green and folded upward along the midvein. Pruning and destroying the witches' brooms, before overwintering eggs have hatched can achieve some control. This will reduce early season populations of aphid. But because not all the eggs will be removed a pesticide treatment may be necessary if unsightly growth is unacceptable. See Cornell Guidlelines for further information.Link to an Informative web page regarding Honeysuckle Aphid place on the web by Morton Arboretum

Magnolia Scale (169)—The black crawlers are1/16 inch long and are located in bark crack. There are several effective parasites and predators.  If scale infestations are small, it may be possible to prune out affected plant parts.  The females can be removed by hand in July before crawlers emerge.  To manage moderate to heavy infestations, apply horticultural oil in April (22-91 GDD50).Link to an INFORMATIVE WEBSITE regarding Magnolia Scale placed on the web by Ohio State University Extension. There are a couple of good photos.

Scouting Report | Feature Article |Things to Look For | Book Shelf | Growing Degree Days | Phenology|

This publication contains pesticide recommendations. Changes in pesticide regulations or human errors are still possible. Some materials may no longer be available, and some may no longer be legal. These recommendations are provided only as a guide.

All pesticides distributed, sold, or applied in New York State must be registered with the Department of Environmental Conservation (DEC). Questions concerning the legality and/or pesticide use in New York State should be directed to the appropriate Cornell Cooperative Extension office or regional DEC office.  Read the label before applying any pesticide. If any information in these recommendations disagrees with the label, the recommendation must be disregarded.

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 Cornell Cooperative Extension Service 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 and examine a current product label before applying any chemical.

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