is a Plant Pathologist and President of Chase Research Gardens, Inc.
C.R.G. is a private research and consulting corporation specializing in
Both hourly and contract services are available.
You can reach C.R.G. at P.O. Box 168, Mt. Aukum, CA 95656 Phone and Fax:
916-620-1624 - E-mail: MTAUKUM@AOL.COM
rhizome rot of Sansevieria
Pathogen - Aspergillus niger
Symptoms - Water-soaked spots on rhizomes become sunken as
they mature. The outer layer may remain intact with inner tissue
disintegrating rapidly. Spots near leaf bases or stem ends form
and frequently contain the sooty dark brown to black spores of the
fungus. The pathogen enters cuttings through wounds created during
cutting collection. The disease is most severe during shipping.
Control - Disease control by keeping soil temperatures below
100°F (using mulches of bark, sawdust or woodchips) is partially
successful. Examine cuttings carefully for signs of infection and
reject those that are not completely healthy. Use new or sterilized
pots and potting media and grow plants away from the native soil.
soft rot on Sansevieria
Pathogen - Erwinia carotovora
Symptoms - A mushy soft rot of the lower end of a cutting.
Sometimes the plants have a fishy, rotten odor, characteristic of
Control - Bacterial rot can be controlled through elimination
of water on leaves. Choice of clean cuttings and strict sanitation
are the most important control measures. Use of bactericides is
not recommended due to very poor efficacy. Many other plants can
be infected by Erwinia spp., and all should be inspected
regularly for soft rot symptoms.
leaf spot of Yucca
pathogen - Cercospora sp.
Symptoms - Initially, rust-colored specks form. Spots expand
to 1/4-inch elliptical areas that are tan to brown.
Control - Protect plants from overhead irrigation and rainfall,
if possible, to diminish spread of spores and the conditions needed
for them to germinate and infect leaves. Remove leaves with symptoms
and do not use cuttings with spots. No fungicides have been evaluated
for control of this disease on yuccas, although thiophanate methyl
has been used to successfully treat other Fusarium diseases. Always
check fungicide labels for legal uses on each plant and follow rates
and intervals as noted on the label.
damage of Sansevieria
Pathogen - Temperatures below 45°F
Symptoms - Leaves are constricted in width in a narrow band
across the leaf blade. Usually, constricted leaves have normal coloration.
Cold-injured leaves develop whitish, water-soaked areas 1 to 4 weeks
after exposure to cold
Control - Maintain temperatures at 45°F or above. Prevent
plant exposure to cold air or cold water (condensate or drips from
the roof of the structure). Low air temperatures account for most
of the injury in open stock beds, while cold water draining through
perforations in polyethylene film used for lining shade houses accounts
for most of the injury to Sansevieria in Central Florida.
Use solid cover structures which are properly heated. Plants which
are over-fertilized (especially with nitrogen) are more sensitive
to chilling than those fertilized appropriately.
or brown leaf spot of Yucca
Pathogen - Coniothyrium concentricum
Symptoms - Coniothyrium leaf spot first appears as tiny clear
zones in older leaves of Yucca. Spots turn yellowish and
finally brown as they mature. They are generally elliptical and
are scattered across the entire upper surface of older leaves. After
about 4 months, black fruiting bodies form in sunken centers and
are easily seen with the naked eye. Sometimes a yellow border forms
around the spots. This disease has been reported on many species
of Yucca including Y. aloifolia, Y. filamentosa (Adam's
needle), and Y. smalliana
Control - One of the most important aspects of control is
the removal of older infected leaves and elimination of overhead
watering or exposure to rainfall. Since most yuccas are grown exposed
to both overhead watering and rainfall, regular applications of
fungicides are needed to prevent disease. Weekly applications of
chlorothalonil (Daconil 2787), zineb (Zineb), or mancozeb provided
excellent disease control experimentally. Check labels of specific
fungicides for yucca as well as rates and intervals of use.
or gray leaf spot of Yucca
Pathogen - Cytosporina sp.
Symptoms - Cytosporina or gray leaf spot of Yucca aloifolia
(Spanish bayonet) has not been adequately described. Symptoms include
tip and marginal necrosis with a predominantly gray color and brown
margin. They often reach 3 inches wide, have concentric rings of
light and dark tissues and are most common on older leaves. The
black fruiting bodies of Cytosporina sp. can be found in
these spots. This disease is not as common today as it was 20 years
Control - Use the methods described for Coniothyrium leaf
spot to control Cytosporina leaf spot of yuccas.
leaf spot on Sansevieria
Pathogen - Fusarium moniliforme
Symptoms - Spots start as tiny water-soaked areas on immature
leaves which rapidly enlarge into elliptical-to-irregular-shaped
areas with a red or tan coloration. They are often surrounded by
a bright yellow margin which can be 1/8-inch wide. As spots merge,
immature leaves become distorted. Under optimal conditions, meristems
of infected shoots die.
Control - Standing water in the central whorl of the plant
is necessary for infection to occur. The high levels of water available
during the rooting process are optimal for disease initiation and
progress in cuttings. Complete disease control can be achieved if
plant foliage is kept dry. Dracaenas are also susceptible to this
pathogen. Chlorothalonil (Daconil 2787) has been especially effective
in controlling Fusarium leaf spot experimentally. Check labels for
legal plants, intervals, and rates.
stem rot on Yucca
Pathogen - Fusarium spp., Nectria spp.
Symptoms - One of the most common diseases of rooted yucca
cuttings is caused by Fusarium spp. Soft rot of stem ends
develops with destruction of leaves as well. There are two types
of fruiting bodies for the pathogen which are commonly produced
on the infected tissue. These are the bright red perithecia, which
are round and relatively easy to see with the naked eye, and the
powdery clusters of conidia, which are ochre-colored
Control - Use only pathogen-free cuttings, use new or sterilized
pots and potting media, and grow on raised benches. No fungicides
have been evaluated for control of Fusarium stem rot on Yucca.
blight on Yucca
Pathogen - Sclerotium rolfsii
Symptoms - This pathogen attacks all portions of the plant
but is most commonly found on stems. White, relatively coarse mycelia
grow in a fan-like pattern and may be seen on the soil surface or
stems. The round sclerotia form almost anywhere on the plant or
soil surface. Sclerotia are initially white and cottony and approximately
the size of a mustard seed. As sclerotia mature, they turn tan,
then eventually, they turn dark brown and harden
Control - Although this disease can be avoided through cultural
methods, it continues to cause losses in production of foliage plants.
PCNB (Terraclor 75) provides the most efficacious control of southern
blight on many foliage plants. Application of this fungicide to
some foliage plants results in stunting, and its use is restricted
to once every 12 months. Check labels for legal plants, intervals,