Contents...
Scouting Report—Conifers:
Canavirgella Needle Disease, Pine Bark Adelgid, Pine-Pine Gall Rust,Ploioderma, Redband Needle Blight, Pine Spittlebugs, Weir’s Cushion Rust
Broad-leaved Trees and Shrubs:
Azalea Sawfly, Azalea Whitefly, Black Spot of Rose, Boxwood Mite, Cedar Apple Rust, Eastern Tent Caterpillar, Euonymus Caterpillar, Japanese Maple Scale, Lace Bugs, Lecanium Scale, Native Holly Leafminer, Privet Rust Mite, Southern Red Mite, Viburnum Leaf Beetle, White Prunicola Scale, Woolly Beech Aphid
Things to Look For—
Boxwood Leafminer, Elongate Hemlock Scale, Euonymus Scale, European Red Mite, Oystershell Scale, Pine Needle Scale, Sycamore Anthracnose, Twospotted Spider Mite
Feature Article—
Walnut Allelopathy (by Dr. Wayne Sinclair)
Growing Degree Days
Phenology
Miscellany— Arborvitae Dieback |
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 2006
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
Canavirgella Needle Disease of Eastern White Pine (2nd Ed-24)—The
fruiting bodies of this disease are visible now. This disease is caused by the
 fungus Canavirgella banfieldii. This
is a recently described fungus that causes damage that has often been previously
attributed to ozone injury and semi-mature tissue needle blight. Luckily, less
than 1% of the white pine trees in most areas appear to be susceptible to the
disease. Symptomatic roadside and forest trees are often spotted in NY, VT, NH,
and ME, but the disease can be found in other areas, and has occasionally been
a problem in landscapes and Christmas tree plantations.
Only the
current year’s needles on susceptible trees are infected by the  fungus.
Infection takes place in June-July and by August the foliage turns a reddish
color. A key symptom of the disease is that needle bases stay green and often
only 1 or 2 needles in a fascicle are infected. By fall the needles bleach out
to a straw color and the asexual stage of the fungus develops. However, these
structures are not very discernable. Another key symptom of the disease is the
development in the following spring of a long gray stripe on the dorsal side of
the needle. The stripe can be 11-85 mm long. The sexual stage of the fungus is
contained within the stripe.
Secondary fungi readily overcome and inhibit the development of
Canavirgella fruiting structures, thus the symptoms can be easily misdiagnosed.
Needles affected by Canavirgella are shed normally. Previously the disease has
been confused with diseases caused by Bifusella and Meloderma. Close observation and
microscopic examination can differentiate these fungi. Since relatively few
trees are afflicted, fungicide control programs will not likely be developed to
help combat the problem.
Pine Bark Adelgid (31)—On Long Island and in Rockland County the pine bark adelgids were hatching
and moving onto the elongating candles of Eastern white pine. They should be
making cotton by now and will be easier to see. This insect usually causes
little damage to healthy trees and is often most noticeable when colonies
develop on the main trunk of a landscape specimen. Insects can be removed from
the bark of trees with a high pressure spray of water. Foliar applications may
be made where populations are high or where trees are growing in stressful
sites or are otherwise unhealthy. Use horticultural oil or insecticidal soap
first.Link
to an INFORMATIVE WEBSITE regarding Pine Bark Adelgid placed on the web by Virginia
Cooperative Extension. There are some good photos on this site.
Pine-Pine Gall Rust (1st Ed-136, 2nd Ed-151)—This
rust is currently sporulating in Central
New York. The dusty bright
orange spores are now evident on the  galls. This rust occurs on two and three
needle pines, most commonly infecting Scots pine, although other species such
as Austrian and mugo pine occasionally become infected. If pine-pine gall rust
is severe but hasn’t yet begun to sporulate in your area, rogue heavily
infected trees or prune infected branches now. Mancozeb or Manhandle‡ can be
used to prevent new infections from occurring. Make three applications at
two-week intervals beginning when the first orange pustules break through the
bark of the galls.Link
to an INFORMATIVE WEBSITE regarding Pine-Pine Gall Rust 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
WEB SITE regarding
Pine-Pine Gall Rust placed on the web by The Plant Disease
Diagnostic Clinic at Cornell University.
Ploioderma Needlecast (1st Ed-12, 2nd Ed-23)—We
recently found the fruiting bodies of the fungus that causes Ploioderma
needlecast on Austrian pine. The  fruiting bodies are now readily visible on
infected needles, so if you believe a tree is infected with this disease now
would be a good time to examine the suspected tree. Look for tan to brown
needle tips or bands on 2005 and
older needles. Examine these needles closely for thin black lines 1-5 mm long
and running lengthwise along any discolored portion of the needle surface.
These are the fruiting bodies. Do not confuse this with red-band (=Dothistroma)
needle blight where short, thin black lines may be evident going around the
circumference of needles that have a reddish appearance.
Sporulation of Ploioderma usually begins within a few weeks
after the appearance of the fruiting bodies, and with warmer and wetter weather
available, they should develop quickly. A quick look at a speciment in the lab showed no spore production yet.
Unless your area is experiencing a very dry spring, you should expect spore
production to begin by the time the new needles begin to emerge from the
fascicle. If you are trying to control this disease, use chlorothalonil [2(ee)
label] and apply the first treatment when the new needles begin to emerge.
Treat two more times at 3-4 week intervals to protect the new growth as it
develops. Remember, you must have a copy of the 2(ee) in hand when treating.Link
to an INFORMATIVE WEBSITE regarding
Ploioderma 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.
Redband (= Dothistroma) Needle Blight (1st Ed-19, 2nd Ed-13) —We
are in a window of opportunity to treat your Austrian pines if they have this
needle blight, caused by Mycosphaerella
pini. The disease resembles deicing salt spray injury in that it is usually
most prevalent on needles in lower portions of  crowns where the outer 1/3 - 2/3 of each needle
has turned brown. The big difference, at least from a distance, is that damage
from redband needle blight is as common on roadside trees as it is on trees far
away from any conceivable salt spray. Also, redband needle blight now will be
prominent on infected 2004 needles while
the 2005 needles are still mainly green. Microscopic exam of affected needles,
especially in the spring, shows abundant production of characteristic 3-4
celled spores. In past years we have regarded redband as a nuisance, but with
the damage we have seen the last several years, a fungicide spray program may
be needed to restore trees to acceptable appearance. Spray with elemental
copper, Camelot, Protect T/O, DF or Junction once at budbreak and twice again at 10 to14 day intervals.Link
to an INFORMATIVE WEBSITE regarding Red
Band Needle Blight placed on the web by the USDA Forest Service.
Pine Spittlebugs (36)—Spittlebugs and their frothy white masses are quite
visible now. Two species are common in New York State. The pine spittlebug attacks pine, native spruce,
balsam fir, Douglas-fir, and hemlock. The Saratoga spittlebug, the more damaging of the two, also causes
yellowing of foliage and may kill twigs, branches and eventually a whole tree.
Light infestations may be removed with a strong stream of water. Treatments can
be made from 148-298 GDD50.
Weir’s Cushion Rust (2nd Ed-143)—Now
is a good time to scout for this needle rust on spruce trees, caused by Chrysomyxa
weirii. Infected needles have conspicuous yellow-orange spots with
spore-bearing pustule in the  center of each. The spores can germinate to
produce smaller spores that will be wind blown to new needles. There is no
alternate host with this rust. It poses the greatest threat to Colorado blue
spruce Christmas trees but will also reduce the value of landscape specimens.
The only registered management strategy is to protect potential hosts with
sprays of chlorothalonil, but be advised that not all growers have had good
luck with chlorothalonil for this disease. Some have opted to eradicate spruce
from their plantations rather than fight a futile battle with the pathogen.
Start treatment when budbreak is 10 percent complete, and make two more
applications at 7 to 10 day intervals.Link
to an INFORMATIVE WEBSITE regarding Weir's
Cushion Rust 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.
Azalea Sawfly—The
larvae of this sawfly were devouring azalea leaves on Long Island on our recent scouting trip. Deciduous azaleas (especially Exbury
and mollis hybrids) are preferred
hosts. The sawflies are light green with an amber head and easily camouflaged
among the foliage. Young larvae feed along the leaf edges, while the older larvae
eat all but the midrib and major veins in the leaves. There is one generation
per year. If necessary, treat with a registered pesticide. Keep in mind that Bacillus thuringiensis is ineffective on
sawfly larvae.
Azalea Whitefly (151)—Adult
whiteflies were just beginning to hatch on azalea in Long Island and Westchester County. The adults resemble tiny white  moths. Medium
infestations may produce noticeable levels of honeydew and sooty mold. Heavy
infestations can cause leaves to turn yellow and drop prematurely. All stages
feed on the underside of leaves. If honeydew or damage is easily identifiable,
spray the undersides of the leaves with insecticidal soap or horticultural oil.
Predators and parasites are frequently used to keep these pests at low levels.
Rake up and destroy fallen leaves from infected plants. If infestations are
intolerable treat with horticultural oil, or other registered pesticide in
early June to Mid-July (448-700 GDD50) and again at 1250-1500 GDD50 and at 2032-2150 GDD50.(Click on Photo for Enlargement)Whitefly
photo courtesy of http://www.forestryimages.org ©Clemson University - USDA Cooperative Extension Slide Series
Black Spot of Rose (1st Ed-28, 2nd Ed-39)—Amy Albam,
Extension Educator from Rockland County, reported someone had recently submitted a sample of
black spot of rose. This seems rather early in the season to already see the
disease but she said it was on the 2005 growth. This disease is characterized
by circular black spots, with fringed borders. The spots are found on the upper
surfaces of leaves and can be up to1⁄2 inch in
diameter. The area around these black spots or the entire leaf may turn yellow.
Purplish-red, raised, irregularly shaped cankers on the first year canes are
another diagnostic symptom. The cankers usually remain small, eventually
turning black. However, they may girdle and kill tender young shoots. Cultural
and chemical control measures are available. See the Cornell Guidelines for
more information.
Boxwood Mite (229)—On
our last scouting trip we found these mites on boxwood in Long Island and
Westchester County. Boxwood is its only host, and this mite is a pest of both
European and American boxwood varieties. Japanese boxwood is less susceptible.
Adult mites are greenish brown. They feed on the underside of leaves and are
difficult to see even with a hand lens. Leaves of infested plants appear to be
pin-pricked or scratched with tiny white or yellow marks. Treat with
insecticidal soap, horticultural oil, or other registered pesticide at 245-600
GDD50.
Cedar Apple Rust (1st Ed-115, 2nd Ed-129) —Bright yellowish orange spots have begun to appear on the leaves of  crabapple.
On the upper surfaces of the leaves, tiny pustules are located within the
spots. Circular lesions can be seen on the lower surface of the leaf, with the
aid of a hand lens. Nothing can be done now to treat this disease. However, be
prepared to treat infected trees next spring. In the future plant resistant
varieties.
Eastern Tent Caterpillar (76)—The well known nests of this caterpillar are  a lot
more prevalent in central New York this year than they have been in the past.
They are easy to spot on wild cherry trees as we drive along the countryside,
especially along the Susquehanna river. We have gotten reports from several
other areas of the state that indicate that there are high populations of this
pest occurring in various areas.Link
to an INFORMATIVE WEBSITE regarding Eastern
Tent Caterpillar placed on the web by University of Kentucky
Department of Entomology. There are several good
photos on this site.
Link
to an INFORMATIVE WEBSITE regarding Eastern Tent Caterpillar placed on the web by the USDA Forest
Service. There are several good photos on this
site.
Euonymus Caterpillar (79)—On May 15th we found the newly
hatched euonymus caterpillars in Central New York. They were only 1⁄8 inch long and
just beginning to form webs. Euonymus caterpillars feed gregariously and
defoliate several  species of euonymus, primarily Euonymus europaea (the tree form), E. kiautschovicus, and E.
alatus. The  larvae feed in colonies that envelop the foliage in large
silken webs. The mature larvae are about an inch long and green or yellowish
green. They have two rows of round black spots and black heads. If the
population is low, prune out infested branches. High populations may require
the use of a registered pesticide. Link to an INFORMATIVE WEBSITE regarding Euonymus Caterpillar placed on the web by University of Vermont Extension.
Japanese Maple Scale—Dan Gilrein, Extension Entomologist reports “So far
this spring I have had two samples of Japanese maple scale, an armored scale.
One was on privet from the south shore area, another on a B&B Japanese
maple specimen, which had been shipped here from an out-of-state nursery. There
was some dieback on the maple, possibly associated with the infestation. Little
is known about its life history, but crawlers will probably be present starting
late May.”
Lace Bugs
(204-206)—We found immature lace
bugs, from the genus  Stephanitis, on
andromeda in Westchester County and Long Island. In addition they feed on other
broad-leaved evergreens such as azalea, and rhododendron. Feeding occurs on the
underside of the leaf, producing varnish-like spots. On the top side of the
leaf, yellow to silver stippling can be seen. Brown patches or black droplets
of excrement, along with molted skins, are indications of a high infestation of
this pest. The nymphs are black and spiny. Adults are 3-4mm long, green-brown,
with intricate wings that appear to be lacy.
We found other lace bugs, from the genus Corythuca, on Amelanchier in  Central New York. Corythuca lace bugs attack deciduous trees and shrubs. Early
detection of lace bug activity is essential for effective management. Their
natural enemies are rarely abundant enough to effectively suppress damaging
populations. To manage Corythuca spp.
lace bugs treat in mid-May (239-363 GDD50) and for Stephanitis spp. treat at 120+ GDD50. For
best control, spray both upper and lower leaf surfaces.Link
to an INFORMATIVE WEBSITE regarding Lace
Bugs- Placed on the web by University of Kentucky Department of Entomology.
AND
Link to WEBSITES of good photograph of sycamore lace bugs (adults and nymps)
Also link to good photos of immature
azalea Lace Bugs and Azalea Lace Bug damage -each placed on the Web by the University
of Florida, Institute of Food and Agricultural Sciences.
Lecanium Scale (174)—Last year populations of lecanium scales were very
high on sugar maples in several areas of the state and Vermont. Their hosts
include many other deciduous trees as well. The copious amounts of honeydew
produced by these scales can be quite a nuisance. On heavily infested trees
twig and branch dieback can occur. Steve
Vandermark, Extension Educator from St. Lawrence Cornell Cooperative Extension
reports this scale has definitely made it through the winter. He is seeing a
massive, widespread population on sugar maple again, on a forest level.
Sometimes the same trees are simultaneously infested with forest tent
caterpillar. Link to an INFORMATIVE WEBSITE regarding the lecanium scales on Maple placed on the web by the Vermont Foresty Division. 
Native Holly Leafminer (95)—The adult native holly leafminers were just  beginning
to emerge on our last scouting  trip. They are small black flies (1⁄8 inch long) and
can be found around the newly expanded leaves. Examine young foliage of English
and American holly for tiny green blisters. Because the parasites do not reduce
the area mined and the resulting aesthetic damage, they can not be relied upon
as a control. Place a sticky trap on the terminals of holly to detect the
adults. To manage large populations, apply a contact insecticide in mid-May
(192-298 GDD50).Link to an INFORMATIVE WEBSITE regarding Native Holly Leafminer placed on the web by Penn State Cooperative
Extension. There are some good photos on this site.
Link to an INFORMATIVE WEBSITE
regarding Native
Holly Leafminer placed on the web by the Center for Integrated
Pest Management, North Carolina StateUniversity. There are several
good drawings on this site.
Privet Rust Mite (231)—We found this eriophyid mite on our last scouting trip
on Long Island. These mites are white to yellow and spindle shaped with four
short anterior legs. Even when viewed with a hand lens, they are so small that
they appear as specks of dust or pollen. The host plants of this pest are the
amur privet, California privet and regal privet. The immature mites suck leaf
juices and introduce toxins that cause leaves to cup downwards and turn olive
green. Premature leaf drop and silvery stippling of foliage are also symptoms.
Predaceous mites are the most effective natural enemies to these pests, but
horticultural oil or other registered pesticides can be used to fight these
pests in the last 10 days of May through Mid-June (298-802 GDD50).
Southern Red Mite (229)—We saw newly hatched southern red mites on  American holly during our scouting trip to
Long Island. They were on both sides of the foliage, although eggs were only on
the undersides. This mite is the most widespread, important, and destructive
spider mite on broad-leaved evergreens such as holly, laurel, rhododendron,
camellia, and azalea. Injury occurs as bronze, stippled foliage. Predators are
usually an effective means of control except under outbreak conditions. Tap
leaves over white paper—spray thoroughly if 10 mites or more per tap are found.
Insecticidal soap or horticultural oil can be used for treatment. See the
Cornell Guidelines for other options.(Click on Photo
for Enlargement)
Link to an INFORMATIVE
WEBSITE regarding Southern
Red Mite placed on the web by the
Center for Integrated Pest Management, North Carolina State University.
There are several good drawings on this site.
Link to a good
photo of southern red mites placed on the web by the University of
Florida.
Viburnum Leaf Beetle (104)—Viburnum leaf
beetle larvae have been out since May 2 in the Ithaca area according to Paul
Weston, Department of Entomology, Cornell University. Paul notes “Larval
populations are considerably lower than  last year, but people in our immediate
vicinity will probably start to see more problems on viburnums in the second tier
of susceptibility (e.g. Sargent viburnum and mapleleaf viburnum) now that many
of the highly susceptible ones (arrowwood and cranberrybush) are gone or on the
way out. This applies to the Ithaca area or areas that have had a similar
amount of time dealing with VLB. In areas that have been more recently
invaded, the greatest problems will probably still be with the most susceptible
viburnums, while in areas that have had a longer history of invasion, the
second-tier species may have already been wiped out.”
Preventative sprays are probably not a good investment. Instead,
wait until larval feeding becomes apparent and then decide whether the
population is large enough to warrant intervention. See Cornell Guidelines for
treatment options.
Link to an INFORMATIVE
WEBSITE regarding Viburnum
Leaf Beetle placed on the web by Cornell University.
Link
to an INFORMATIVE WEBSITE about Viburnum
Leaf Beetle- Placed on the Web by Ontario Ministry of Agriculture,
Food and Rural Affairs.
White Prunicola Scale (188)—At our scouting sites in Long Island and  Westchester
the white prunicola scales had begun laying their eggs. Expect the crawlers to
hatch soon.
Woolly Beech Aphid (140)—On our last scouting trip to Westchester and Rockland
Counties we found woolly beech aphids on beech; apparently its only  host. Each
aphid has a quantity of waxy wool-like filaments that extrude from its body.
Large numbers of cast “skins” may be found attached to leaf hairs, adding to
whitish appearance of the leaf. This pest causes sooty mold, small leaves, and
dead twigs. The natural enemies of these aphids seem to keep their numbers
down, but registered pesticides can be used if infestations are intolerable.
The treatments should be administered late in May through mid-June (363-707 GDD50) Link to a web site regarding Woolly Beech Aphid . This site has good photos.
Scouting Report | Feature Article |Things to Look For | Miscellany | Growing Degree Days |
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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