DISEASES OF CHRISTMAS TREE SEEDLING AND TRANSPLANT BEDS
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Dr. Sharon M. Douglas
Department of Plant Pathology and Ecology
The Connecticut Agricultural Experiment Station
123 Huntington Street, P. O. Box 1106
New Haven, CT 06504
Phone: (203) 974-8601
Fax: (203) 974-8502
Founded in 1875 Email: Sharon.Douglas@po.state.ct.us
Putting science to work for society Website: www.ct.gov/caes
DISEASES OF CHRISTMAS TREE SEEDLING AND
TRANSPLANT BEDS
Growing and maintaining a plantation of • Source of water for irrigation readily
healthy Christmas trees starts with healthy available.
seedlings and transplants. Whether you are • Fumigation- Compounds for fumigation
starting with seeds, seedlings, or transplants, are limited in availability and are
there are a number of issues that should be generally extremely toxic. Therefore, it
considered and addressed prior to or at is often suggested that they be used only
planting time that will help to avoid or in areas with a history of soil problems.
minimize problems from developing right Soil fumigation is best done in late
from the start. This fact sheet is divided into summer or early autumn when the soil
two parts: Part 1 covers general factors for temperature is relatively high and soil
consideration prior to planting and Part 2 moisture is usually within a moderate
covers common disease problems at various range. Among the compounds registered
stages in production (seed beds, seedling in Connecticut is metam sodium
and transplant beds, and field-planted (Vapam).
transplants).
2. Seed Selection-
Part 1. General Factors for It is important to use seed of good quality
Consideration Prior to Planting from a known source. Fungal contamination
is more common in dirty seed lots and poor
1. Site Selection for Seedling and quality seed often has reduced germination
Transplant Beds- percentages and produces weak seedlings
When selecting a location for seedling and that are more vulnerable to disease.
transplant beds, it is important to consider
the following factors and characteristics of 3. Planting Stock and Transplants-
the site: Several different types of stock are now
available for planting. When selecting
• Sunny location away from frost pockets
transplants, characteristics of the planting
and protected from sweeping winds.
site should dictate the type of stock that you
• Well-drained soil, preferably a loam or
select. Among the factors for consideration
sandy loam, with moderate fertility and
are: 1) amount of competition from other
pH 5.5-6.2.
vegetation (e.g., grasses, shrubs), 2) soiltype, 3) season of planting, and 4) risk of • Due to their larger size, they are more
browsing (in areas with high populations of difficult to plant when compared to
wildlife such as deer). container stock and root placement is
Examples include: critical;
• When competition from vegetation is • Once the seedlings are lifted from the
expected- larger stock might out- nursery beds they are perishable – they
perform smaller stock. must be kept cool and moist until
• When extreme site conditions are planting;
encountered (e.g., shallow soils or rocky • Generally, bare root stock is more
sites)- container stock might be easier to expensive than container stock.
plant because of its smaller root plug and
can be easier to establish. Container Stock
Once used mostly by the forest industry,
Bare Root Stock container stock is now available at some
This is the most common seedling type nurseries. There are many different types.
available to landowners. Bare root seedlings Typically, container stock is grown for eight
are grown outdoors in nursery beds and to nine months in a controlled environment
shipped without soil on their roots. Once (greenhouse) and is overwintered outside
removed from the beds, they must be kept before being shipped to the planting site the
cool and moist to keep the roots alive. following spring. The seedling roots form a
Typically, bare root seedlings are two to plug with a soil-less growing medium.
three years old and their height can range Depending on the species and container size,
from 6 inches to 2 feet, depending on the they typically range from 3-6 inches in
species and age. Some nurseries also have height and the root plug measures 2 inches
transplant seedlings available. Bare root in diameter by 4 inches in length.
seedling stock is lifted from high-density Advantages and disadvantages:
seedbeds and then replanted in new beds at a • Generally less expensive to purchase;
lower density. This results in a seedling that • Ease of planting (small root plug)
will generally have a more fibrous root, generally results in better planting
larger stem diameter, and a better shoot-to quality;
root ratio. Transplant stock is generally a • Easier to plant in areas of shallow or
little more expensive to produce and may very stony soils (small root plug);
cost a little more to purchase, but this stock • Extended planting season;
type is more robust and may be more suited • Can be easily grown in different
to some planting sites. container sizes to meet the
Advantages and disadvantages: characteristics of the planting site;
• Greater availability both in the variety of • Limited species availability and not
species and in the number of nurseries readily available at most nurseries;
selling this type of stock; • Generally requires good site preparation
• Has a larger root system that provides of the planting site and follow-up
greater rooting depth; tending to reduce competition;
• Less susceptibility to frost heaving; • Smaller size (top and root) makes it a
• Larger than container stock, it is better poor match for planting sites with heavy
suited to planting sites with higher levels competition.
of competition;
Diseases of Christmas Tree Seedling and Transplant Beds S. M. Douglas 2
The Connecticut Agricultural Experiment Station (www.ct.gov/caes)Characteristics of Quality Seedlings good straight taproot with an abundance
Seedlings and transplants should be of fibrous or “feeder” roots. A taproot
purchased from reputable nurseries in order with minimal feeder roots or one that is
to avoid introducing disease problems into crooked, twisted, or J-shaped are signs
the plantation. Although this helps to of poor quality stock, which will
minimize problems, there is no guarantee of probably result in a transplant that is
quality, so each shipment of seedlings or slow-growing, generally weak, and
transplants should be carefully inspected as prone to disease.
follows: • Gently scrape the surface of some of the
• Open the package as soon as it arrives to finer roots with your fingernail to check
check if the seedlings have been on their health. If the root is healthy, the
properly handled and packed so that the woody portion should be white. If it
roots are still moist. If the roots are appears brown, tan, or gray, it can
shriveled and dried out, survival may be indicate that the roots have been infected
low once they are planted. with a root rot organism at some point in
• Foliage should be green and fresh and their growth. This can influence
under NO conditions should there be any survival once they are planted but more
visible mold or fungal growth. If there importantly, can serve as a means for
is gray mold on the needles (probably introducing unwanted root rot organisms
Botrytis cinerea), it is probable that the into a seedling or transplant bed and
seedlings have been in storage too long ultimately, a plantation.
or were not properly packed or handled • Maintain good records on each seedling
during transport. Botrytis can kill and lot and planting. This will allow you to
injure foliage and stems so it can trace the source of a problem should one
substantially reduce the number of develop.
seedlings that survive once planted.
• Seedlings should have a good height-to- Remember - do not select seedlings based
diameter ratio. This is the ratio of the solely on one characteristic. It is important
shoot height to the stem diameter (height to look for seedlings that have a balance of
÷ diameter). A seedling with a high ratio all these attributes.
(i.e., >120) is less sturdy then a seedling
with a lower ratio (i.e.,This is a common disease that affects seeds but light waterings and adequate light help
and young seedlings of many plants, to reduce disease development.
including conifers. It can be divided into
two stages based on the stage of the seedling 3. Fungicides are generally not suggested
when it is attacked. since they usually provide poor control and
i. Causal Agents: Rhizoctonia, Pythium, can damage tender seedlings. Among the
Phytophthora, Fusarium compounds registered in Connecticut are:
ii. Symptoms: Pythium and Phytophthora- thiophanate-
Pre-Emergence (before seedlings emerge): methyl plus etridiazole (Banrot),
difficult to diagnose since the affected seeds mefenoxam (Subdue MAXX), and
aren’t visible; best recognized as skips in the etridiazole (Terrazole, Truban). Rhizoctonia
planting bed where no seedlings have and Fusarium- thiophanate-methyl plus
emerged; if you dig into the soil, you will etridiazole (Banrot), thiophanate-methyl
often find that the seed has been attacked (AllBan, Cleary’s 3336), PCNB (Terraclor,
and rotted; Defend).
Post-Emergence (after seedlings emerge):
newly emerged seedlings topple over and B. Drought- Seedlings are quite vulnerable
collapse; there is often a brown to drying so it is important to maintain
discoloration or constriction at the soil line; adequate soil moisture, especially in the
another form of this stage of damping-off is early stages of development.
“cotyledon blight” that occurs when the seed
coat clings to the newly expanding needles C. Excess Water- Seedlings are sensitive
and the fungi present on the seed coat infect to waterlogged soil so it is important to
the seedling; avoid
iii. Management: (Table 1) overwatering.
1. Start with quality seed since fungal
contamination is more common in dirty seed D. Heat- It is helpful to provide adequate
lots. Additionally, poor quality seed often shade and mulch to keep the surface soil
has reduced germination percentages and temperature from getting too high since
produces weak seedlings which are more physical contact with high temperatures can
vulnerable to disease. kill tender roots and desiccate the stems of
young seedlings.
2. Follow cultural practices that maximize
germination and growth of the seedlings. E. Fertilizer Burn- Although developing
The faster the seeds germinate and emerge seedlings need fertilizer, it is important to
from the soil, the lower the risk of damping- avoid over-fertilizing since this can injure
off. It is also helpful to avoid oversowing and burn young seedlings.
and overcrowding of the seedling bed.
Attention to soil pH and providing frequent
Diseases of Christmas Tree Seedling and Transplant Beds S. M. Douglas 4
The Connecticut Agricultural Experiment Station (www.ct.gov/caes)Table 1. Environmental conditions and cultural practices affecting damping-off in container
conifer nurseries.
Environmental Impact on Disease Development
condition or cultural
practice Promote Disease Discourage Disease
Seed quality Dirty or contaminated; slow, weak Clean and sterile; vigorous germination
germinants
Growing medium Contaminated Pest-free
Fine-textured Mixture of particle sizes
Over-compacted Good porosity
pH High (>6.5) Acid (4.5-6.0)
Growing density Oversowing One seedling per cavity
Nutrition High nitrogen Well-balanced fertilization especially
phosphorus, potassium, and calcium
Irrigation Frequent, heavy applications Frequent, light applications
Growing environment High humidity Moderate humidity
Low light Adequate light
Extreme temperatures Ideal temperatures
2. DISEASE PROBLEMS OF white root tips whereas diseased roots
SEEDLING AND TRANSPLANT BEDS exhibit varying degrees of water-soaking
The most common diseases of seedlings and and discoloration, often appearing brown or
transplants are root rots and Botrytis blight black.
but seedlings are also affected by drought,
excess water, heat, and fertilizer burn as Fusarium Root Rot
outlined in the previous section on seed i. Causal Agent: Fusarium spp.
beds. ii. Symptoms: This disease can occur on
A. Root Diseases spruces, true firs, and pines but is most
Seedlings and transplants affected by root severe on Douglas-fir. Symptoms appear as
rots may show a variety of aboveground scattered chlorotic or curled needles. There
symptoms. One of the first indications of is also tip dieback, wilting, and stunting.
root disease is a general loss of vigor, Roots lack fine root development and show
followed by needle-tip dieback, needle extensive cortical decay so the epidermis
curling, chlorosis, and wilting. Even a low can be easily stripped or pulled away from
level of root involvement can severely the core tissues. Yellow to orange fruiting
reduce seedling growth by injuring the root bodies and spore masses can sometimes be
tips and therefore interfering with water and seen on the stem of an infected seedling.
nutrient uptake. Healthy roots have many
Diseases of Christmas Tree Seedling and Transplant Beds S. M. Douglas 5
The Connecticut Agricultural Experiment Station (www.ct.gov/caes)Pythium and Phytophthora Root Rots The most damaging foliage disease of
i. Causal Agents: Pythium spp. and seedlings and transplants is Botrytis blight.
Phytophthora spp. This disease can occur on all conifers.
ii. Symptoms: All conifer seedlings are
susceptible. The primary symptom is wilt Botrytis Blight or Gray Mold
followed by chlorosis and stunting. With i. Causal Agent: Botrytis cinerea
Pythium, the roots appear black and water- ii. Symptoms: Botrytis blight is identified
soaked and are often hollow and collapsed. by the gray, cottony growth of the fungus on
Since the fungus attacks the root tips, the the surface of affected needles and shoots.
root system has very few lateral roots. With The fungus usually moves from the needles
Phytophthora, infected roots develop a to the shoots and into the stems. As the
distinctive reddish-brown discoloration of disease progresses, infected shoots become
the cambial regions. water-soaked and brown lesions develop. If
the fungus spreads to the main stem, it can
Rhizoctonia Root Rot canker and eventually girdle and kill the
i. Causal Agent: Rhizoctonia spp. shoot. The fungus is an aggressive
ii. Symptoms: All conifer seedlings are saprophyte so infections often begin on
susceptible. The primary aboveground shaded, senescent needles and plant debris at
symptom is a general decline and eventual the base of a seedling.
wilting and death of the seedling. Infected iii. Management:
roots are discolored and darkened and there 1. Follow good cultural practices to keep the
is a noticeable lack of feeder roots. seedlings as healthy as possible. Weak and
frost-damaged tissues are particularly
Management of Root Rots: susceptible to infection.
1. Root diseases are more easily prevented
than controlled!! Attention to site selection 2. Avoid overcrowding to allow for good air
for the transplant bed and proper planting circulation.
are critical. It is also important to carefully
inspect stock before planting. If a problem 3. Avoid overhead irrigation or water early
develops, it might be helpful to check in the day so the foliage has a chance to dry.
irrigation water as a potential source of the
fungus. 4. Practice good sanitation. Remove all
plant debris as soon as it develops.
2. Fungicides- These compounds are
preventative and not curative so they are 5. Fungicide sprays- Among the compounds
primarily used to limit the spread rather than registered for use in Connecticut are:
cure the disease. Among the compounds mancozeb (Protect, Dithane), chlorothalonil
registered in Connecticut are: Pythium and (Daconil, Bravo), and thiophanate-methyl
Phytophthora- thiophanate-methyl plus (Cleary’s 3336, AllBan).
etridiazole (Banrot), mefenoxam (Subdue
MAXX), and etridiazole (Terrazole, 3. DISEASE PROBLEMS OF
Truban). Rhizoctonia and Fusarium- TRANSPLANTS IN THE FIELD
thiophanate-methyl plus etridiazole Assuming a proper site has been selected
(Banrot), thiophanate-methyl (Allban, and good planting practices are used, newly
Cleary’s 3336), PCNB (Terraclor, Defend). transplanted stock is most vulnerable to root
B. Foliage Diseases injury from drought stress, especially in dry
Diseases of Christmas Tree Seedling and Transplant Beds S. M. Douglas 6
The Connecticut Agricultural Experiment Station (www.ct.gov/caes)years. However, once out-planted in the
plantation, transplants are also vulnerable to B. Winter Injury or Frost- Newly
many of the diseases found on mature trees planted trees are susceptible to quirky
(e.g., Rhabdocline needlecast, Diplodia winter conditions and spring frosts.
blight). These diseases are not covered in Damage might not be visible until the
this fact sheet but information is available in following spring or summer.
the fact sheet entitled Disease Problems in
Connecticut Christmas Tree Plantations. C. Excess water- Waterlogged soils limit
growth of new roots and inhibit the
A. Drought- As a direct result of the ability of existing roots to absorb water.
transplant process, newly transplanted These conditions represent a challenge
stock is very susceptible to drought for newly planted seedlings.
stress. Therefore it is important to
provide water for those transplants in
years when natural rainfall is limited.
June 2008 (revised)
Diseases of Christmas Tree Seedling and Transplant Beds S. M. Douglas 7
The Connecticut Agricultural Experiment Station (www.ct.gov/caes)You can also read
