 |
JUNIPER
TIP BLIGHT
|
Phomopsis
juniperovora,
Kabatina
juniperi,
or
Sclerophoma pythiophila
|
|
|
 |
|
Introduction
Juniper tip blight, a progressive dying back of twigs and branches,
can be caused by one of three fungi, Phomopsis juniperovora, Kabatina
juniperi, or Sclerophoma pythiophila. These diseases
are devastating to young trees and hedges; trees more than five years
old are less seriously damaged. In addition to many species of juniper,
arborvitae, white cedar, cypress and false-cypress are susceptible
to P. juniperovora. K. juniperi infects juniper species primarily,
but S. pythiophila infects needles of pines, Douglas-fir,
and eastern larch, and twigs of juniper.
Symptoms
Blight symptoms first show up on recent growth of the lower branches.
Dieback begins with shoot tips, and progresses back toward the main
stem (Fig. 2). Death of the
entire plant may result where P. juniperovora and/or K.
juniperi infections are involved. S. pythiophila infection
often follows winter injury, but usually doesn't kill whole plants.
Drought, freezing, dog urine, and transplant shock can cause similar
dieback symptoms. However, if fungi are the cause, they will produce
small black fruiting bodies (up to 0.5 mm in diameter) on recently
killed leaves (Fig. 1) and stems and thus aid in diagnosis of juniper tip blights.
Figure 1: Small, black fruiting
bodies of the fungus. |
Figure 2: Dieback of shoot
tips.
|
|
Disease cycle
P. juniperovora, K. juniperi and S. pythiophila
overwinter in killed twigs and bark on the shrub or on the ground.
Fruiting bodies of the fungi develop in the spring and, during
wet weather, release many spores capable of causing new infections.
P. juniperovora attacks young succulent shoot tips
and may also enter the plant through wounds. Infections can
occur throughout the summer. K. juniperi attacks one
year old growth in the fall, with symptoms showing up in early
spring. The fungus may enter the plant through wounds, as well.
If wet weather prevails, these fungi will spread throughout
the shrub in the course of a few years or less. S. pythiophila
attacks shoots weakened by winter injury.
Management Strategies
Infected twigs and branches should be pruned about two inches
into live wood and destroyed. Prune only when plants are dry,
and sterilize tools between each cut by swabbing them with a
solution containing 1 part rubbing alcohol and 3 parts water or use a solution of 1 part household bleach to 9 parts water..
Plants should be spaced so as to provide good ventilation. This
will reduce high moisture conditions which favor these diseases.
Water in early morning only. Wounding during transplanting and
during cultivation should be avoided for similar reasons. Do
not over-fertilize. Prune out diseased branch tips during dry
weather but avoid excessive shearing.
In New York State no fungicides are specifically registered
for use against Sclerophoma. Kabatina may be listed on some thiophanate-methyl
labels, but most of those products are restricted-use. Most products that are available for homeowner
use are specifically labeled for treating Phomopsis or
generally labeled to treat "twig blight" on Juniper.
These include some products containing the active ingredients:
copper, potassium bicarbonate, or propiconazole. Heritage is also labeled for Phomopsis, but treatments should he alternated with a pesticide with a different mode of action. Some products will require the
addition of a spreader-sticker and should be applied every 2
weeks throughout the growing season. Follow label directions,
and be certain any formulation(s) of pesticide(s) you purchase
are registered for the intended use. Additional products may
be available for commercial use. Commercial applicators should
refer to the appropriate commercial pest management guidelines,
or contact their local Cooperative Extension Office for more
information on currently registered products.
Updated, SLJ, 3/09
This publication contains pesticide recommendations. Changes in pesticide
regulations occur constantly, some materials mentioned may no longer
be available, and some uses may no longer be legal. All pesticides distributed,
sold, and/or applied in New York State must be registered with the New
York State Department of Environmental Conservation (DEC). Questions
concerning the legality and/or registration status for pesticide use
in New York State should be directed to the appropriate Cornell Cooperative
Extension Specialist or your regional DEC office. READ THE
LABEL BEFORE APPLYING ANY PESTICIDE. __________________________________________________________________________________
The Plant Disease Diagnostic Clinic
at Cornell University is located at 334 Plant Science Building,
Ithaca, NY, 14853. Phone: 607-255-7850, Fax: 607-255-4471,
Email: kls13@cornell.edu
or slj2@cornell.edu
|