North Carolina State University


Contents (this page):
Seed Decay
Damping Off
Top Damping Off
Seedling Root Decay
Black or Charcoal Root Rot
Cylindrocladium Root Rot
Cylindrocladium Foliage Blight
Seedling Disease Management and Control

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Seed, Nursery, and Seedling Diseases




Seed Decay

Major Factors Influencing Seed in Storage

  • High Moisture and High Temperature                                                                                   Seed stored improperly often decay. Moisture and temperature are the two most important factors in proper seed storage: low moisture and low temperature discourage seed decay.

Sycamore seeds with their 
coats removed.

fungi growing on sycamore seed

Fungi growing on sycamore 
seed after storage in a moist,
warm condition.


 
fewer colonies at lower temp
Fungi cultured from sycamore seeds stored at various temperatures. 
Note the fewer colonies at the low temperature.



Damping Off of Forest Tree Seedlings



note large areas devoid of seedlings
Pre-emergence damping off is first seen as poor stand development. This slide shows large areas in beds devoid of seedlings. This most frequently is indicative of seeds or germinated seeds killed due to infection by one of several fungi prior to emergence from the soil.

 
new seedlings have toppled over

Post-emergence damping off.
Note how the newly emerged seedlings have toppled over in the containers. The fungus
has infected the seedling at the ground line causing tissue to collapse and become necrotic.
 

Pre- and post-emergence damping off results in a poorly stocked stand.


sweetgum seedlings
Pre- and post-emergence damping off also can occur on hardwood seedlings 
as seen with these sweetgum plants



Top Damping off


necrosis of needles

Top damping off, although rare, is spectacular when it occurs. In this type of damping off, 
pathogens that cause pre- and post-emergence damping off are splashed onto foliage 
of older seedlings and cause necrosis of the needles killing the plant in most cases.




Seedling Root Decay


extensive root decay

Many of the same fungi that cause damping off also can infect roots later in the season 
causing a root necrosis that is usually first seen as chlorotic and necrotic foliage and 
stems.  Examination of seedlings showing these symptoms reveals extensive root 
decay as seen on the right.




Black or Charcoal Root Rot

 

root showing typical symptoms

Major symptoms are decay of feeder
roots and hypertrophy and hyperplasia
of large roots and root collar area.
 The enlarged areas become dark brown 
to black.

Compare the root systems of a healthy 
seedling (left) with that of an infected
seedling (right).


 
healthy root
infected root

Cross section of a healthy root (left) and an infected root (right).  Note the number 
and size of cortex and bark cells of the infected root compared to the healthy root.


Foliar symptoms as a result of
root infection. Note the fungus
has parasitized the roots not
the foliage.




Cylindrocladium Root Rot

microsclerotia


red pine
         Red pine
black spruce
                              Black spruce
fraser fir
         Fraser fir
black walnut
                              Black walnut

Foliage symptoms showing chlorosis, necrosis, and defoliation.


note dark color
feeder roots have been decayed

Root and root collar symptoms on yellow poplar (middle and right) and sweetgum (left). 
Note the dark color both internally and externally. Feeder roots are also decayed.


Conidiophores and clumps of conidia of Cylindrocladium scoparium on a piece of root tissue (right) and conidia (the long slender spores on the left).

 
 
microsclerotia microsclerotia germinating microsclerotia

The left and center photos show microsclerotia in root segments. On the right is a germinating microsclerotia. Note that several hyphae are produced from a single microsclerotium.




Cylindrocladium Foliage Blight


infected white pine seedlings
chlorosis and necrosis of needles

Cylindrocladium spp., under the proper conditions, can have spores rain-splashed or 
blown onto foliage causing a blight.   Note the chlorosis and necrosis of the needles 
on these 2-year-old white pine seedlings.



Seedling Disease Management and Control


The most common practice to manage soilborne pathogens
is by soil fumigation using a methyl bromide-chloropicrin combination. This chemical is injected in prepared beds and covered with a polyethylene tarp for a minimum of 48 hours. Modern equipment has been developed such that chemical injection, tarp placement and sealment of tarp edges with a layer of soil is done in a one step operation.

 

note untreated bed in foreground

Results of soil fumigation in a nursery that had damping off and root 
decay problems.  Note the untreated beds in the foreground.
 

Foliar fungicides can be applied if a foliar disease is involved.
 

A healthy, well managed nursery of pine seedlings.
 

Some photos provided by:
Russ Bullock
M. K. Beute
C. Cordell
G. Fakir
 

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This website was prepared by Becky Bernard.
Last updated on 04 February 2008 by M.J. Munster