October 2003
Vol. 13, No 10
Northeast
GREENHOUSE IPM NOTES
A Publication from Cornell & Rutgers Cooperative Extension
Current Situation…
Wet conditions have promoted infectious diseases on
greenhouse and field grown crops. Foliar problems
with rusts a variety of leaf spots and powdery
mildews are common. We expect a significant
population of fungus gnats and shoreflies. Bracts
have initiated and will begin to color soon so it is
critical that any disease or insect problems are
addressed now!
Growers of healthy crops emphasize environmental
and cultural tactics that minimize disease and insect
problems. Insure proper and uniform temperatures
throughout crops. In other words be sure that sensors
are accurate and that air circulation minimizes cold
spots. Condensation on foliage and moist soils in
cold areas favor foliar and root diseases. Finally,
don’t crowd plants!
Cooling temperatures will favor Botrytis - Botrytis
cinerea causes stem and foliar blight early in
production, especially when newly-potted cuttings
are not provided with good air circulation. Infected
areas are light brown in color; leaf lesions are large,
irregularly shaped blotches. Some cultivars are
more susceptible than others; these should be placed
in the least-humid growing areas within the
operation. Watering practices should be designed to
keep foliage dry as much as possible; water early in
the day, and use fans for good air circulation.
Fungicides can supplement a good environmental
control program. Use rotations of Decree, Daconil,
Spectro, Phyton 27, Kocide 2000, Heritage,
Dithane, Protect, Compass, Vorlan and Chipco
26019 for Botrytis management.
Pythium root rot on ‘Jingle Bells’
Black Root Rot, caused by Thielaviopsis basicola,
has been troublesome on fall pansies. Growers
should monitor crops closely for symptoms that first
resemble a nutritional deficiency or stunting.
Overwatering
and
inappropriate
nutrient
management may increase problems to the point
where roots turn black and rot. Diseased plants are
difficult to cure so early detection and roguing are
essential. For pansies, maintain media pH at about
5.5. This is lower than most crops, but is necessary
for reducing disease problems. Fungicides are
labeled and effective when problems are caught
early.
Pythium Root Rot was diagnosed on Poinsettias
(Cortez, Jingle Bells and Marblestar White).
Pythium infections are favored by overwatering and
high media salts from excessive fertilizer.
Cooperating Agencies: Rutgers, the State University of New Jersey, U.S. Department of
Agriculture and County Boards of Chosen Freeholders. Educational programs are offered without
regard to sex, race, color, national origin, disability, or age. Rutgers Cooperative Extension is an
Equal Opportunity Employer.
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Whiteflies are active in greenhouses. We are seeing
the bandedwinged species, which enters
greenhouses from outdoors. Although it has been
reported as a pest on some crops, populations
associated with poinsettias have not been
troublesome. Greenhouse and silverleaf whiteflies
were also detected in significant numbers on sticky
cards.
Poinsettia Scab Update
Laurie Scullin, Director of Marketing, Paul Ecke
Ranch
Pythium root rot is causing wilt on ‘Jingle Bells’.
Fungus Gnats continue to trouble growers. Wet
conditions this spring and summer should increase
problems this fall. Poinsettias are most vulnerable
during propagation when cuttings can be lost, but
remember feeding is not the only risk; fungus gnats
spread root disease pathogens and annoy customers!
This fall we will be conducting a field trial to
evaluate chemical and biological control of fungus
gnat larvae that originate beneath greenhouse
benches. Thanks to the New Jersey Association of
County Agricultural Agents, South Jersey Flower
Growers, Ludvig Svensson, Inc. and Griffin
Greenhouse and Nursery Supply Inc for providing
support for this work.
Insect box, constructed with Econet screen, set up to evaluate
biological and chemical control of fungus gnats that originate
from greenhouse floors.
This is the time of year we get a few scab calls.Just
after propagation is the time we easily see visible
symptoms. Scab is a minor problem on the poinsettia
crop. A few years ago we had concerns that scab was
going to be more of an issue, but it has to date
become no more than a minor disease in the
poinsettia crop. Scab is not known to infect non
poinsettia crops and does not over-winter outside
live poinsettia plant tissue.
As a refresher - regarding scab on poinsettias:
Scab is a disease known to poinsettias and is seen in
warmer regions of the world. It is spread primarily
by splashing water. It does cause lesions and other
abnormalities on poinsettias, which makes it fairly
easy to detect in more advanced cases of the disease.
There is no test kit for this disease, a positive
identification would need to come from lab analysis.
We see cases each year of suspected scab due to
other physiological conditions, the most common
being spray damage. Early stages of scab are often
confused with mechanical, spray, and even other
fungi such as botrytis, or the physiological disorder
of odema.
We do see this disease within crops and production
from time to time. It is not a 'death and destruction'
disease in that, if a plant has it, the whole crop is at
risk. Rather, if the disease is seen, we recommend
discarding the infected plant(s), inspecting the
surrounding plants carefully, and beginning a
treatment program with fungicides. There are several
fungicides effective against scab. The most
susceptible phase of production is in propagation,
and the few weeks after prop due to the larger
Cooperating Agencies: Rutgers, the State University of New Jersey, U.S. Department of
Agriculture and County Boards of Chosen Freeholders. Educational programs are offered without
regard to sex, race, color, national origin, disability, or age. Rutgers Cooperative Extension is an
Equal Opportunity Employer.
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amounts of water being applied to the crop, and to
the overhead irrigation. Once the crop is in a
finishing greenhouse, it is rare to see the disease
spread. Many growers today are using the fungicides
noted in this link anyway as part of their cultural
program for control of botrytis and powdery mildew.
For information on how to detect and treat scab please visit our Tech Help Bulletin Board at:
http://www.eckeranchtechhelp.com/
For more information about Scab:
http://www.ecke.com/scabupdate/index.html
Poinsettia Federal Disease Control Chart:
http://www.ecke.com/html/fastfax/pdfs/Poin%20di
sease.pdf
Subscription Information:
12 monthly issues of the Greenhouse
IPM Notes are offered for an annual fee of
$40.00.
Anyone wishing to subscribe for 2004 may do so
by sending a check for $40.00 payable to CCBA
Send to: Rutgers Cooperative Extension of
Camden County, Attention Agricultural Program,
152 Ohio Avenue, Clementon, NJ 08021
Editor
Comments and suggestions welcomed.
Please contact the editor:
James D. Willmott
Rutgers Cooperative Extension
152 Ohio Avenue
Clementon, NJ 08021
856-566-2900 ext 227
email: [email protected]
The use of trade names does not imply endorsement by
Rutgers or Cornell Cooperative Extension.
This publication contains pesticide recommendations.
Changes in pesticide regulations occur frequently and
human errors are possible. Some materials mentioned
may no longer be available, and some uses may no
longer be legal. All pesticides distributed, sold or
applied in New York or New Jersey must be registered
with the New York State DEC or New Jersey DEP.
Questions concerning the legality and registration status
for pesticide use should be directed to the appropriate
Cooperative Extension Specialist or your regional DEP
or DEC office. READ THE LABEL BEFORE APPLYING
ANY PESTICIDE.
Cornell Cooperative Extension in New York State
Provides Equal Program & Employment Opportunities,
New York State College of Human Ecology, and New
York State College of Veterinary Medicine at Cornell
University, Cornell Cooperative Extension, County
Governing Bodies and United States Department of
Agriculture, Cooperating. Cooperating agencies:
Rutgers, The State University of New Jersey, US
Department of Agriculture and Camden County Board
of Chosen Freeholders. Educational programs are
offered without regard to race, sex, handicap, color,
national origin or age.
White cottony mycelia along with black sclerotia are signs of
Sclerotinia blight on the stem of this cleome.
Cooperating Agencies: Rutgers, the State University of New Jersey, U.S. Department of
Agriculture and County Boards of Chosen Freeholders. Educational programs are offered without
regard to sex, race, color, national origin, disability, or age. Rutgers Cooperative Extension is an
Equal Opportunity Employer.
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