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
Pathogen - Colletotrichum gloeosporioides
Symptoms - Leaf and stem spots appear as soft areas with
sunken centers. These spots can turn black or tan depending upon
the plant. The spores of the fungus are orange colored and are easily
transferred by splashing irrigation water or rainfall.
Control -This disease is rarely a problem on mature or well
rooted plants as wounds appear to be critical for infection to occur.
For this reason special care in protecting rooting cuttings can
generally control the problem completely. Plants that are susceptible
include: Crassula, Graptopetatum, Sedum, and Sempervivum.
blight on Senecio
Pathogen - Botrytis cinerea
Symptoms - Botrytis blight usually appears on leaves of cuttings
in contact with the potting medium or in the center of the plant
where the humidity stays high. The water-soaked spots enlarge rapidly
to encompass a large portions of the plant. When night temperatures
are cool, day temperatures warm, and moisture conditions high, the
pathogen readily sporulates on infected plant parts, covering them
with grayish-green dusty masses of conidia (spores).
Control - Controlling Botrytis blight on most plants is particularly
important during the winter months in the Southeastern US. Methods
which improve drying and reduce moisture condensation on plants
during the nights reduce the need for fungicide application. Iprodione
(Chipco 26019 50WP) and vinclozolin (Ornalin 50WP) are effective
in controlling Botrytis blight on many plants but labels must be
checked for legal uses on each plant. This disease is rarely found
in commercial production of succulents and cacti.
rot on Opuntia
Pathogen - Dichotomophthora indica
Symptoms - Spots are generally tan and may be dry at times
and appear sunken. The black spores of the pathogen are sometimes
found within the spots, and they spread easily by splashing water.
There are only a few cacti reported as hosts of this pathogen (Opuntia
and Gymnocalicium), however many more are probably susceptible.
Control - See controls listed for Helminthosporium blight.
rot on Faucaria and christmas cactus
Pathogen - Fusarium oxysporum
Symptoms - Dieback, root and cladophyll rot may occur as
a result of the Fusarium infection. Species of Schlumbergera, Rhipsalidopsis
and indeed most cacti and succulents produced commercially are susceptible
to F. oxysporum. An infection appears at the cladophyll border or
in plant centers. Spots are generally tan and may be dry at times
and appear sunken. The orange-colored spores of the pathogen form
in the lesions, and they spread easily by water or air since the
spores are light weight. Abscission of cladophylls above the affected
portion can occur when conditions are wet and warm. In addition,
when moisture is high the mycelium of the fungus can develop extensively
and cover the entire plant. Nearly all cacti and succulents are
susceptible to Fusarium diseases.
Control - Use the same cultural controls as listed for soft
rot. Thiophanate methyl (Domain or Cleary 3336) is labeled for use
on some cacti and is effective in controlling Fusarium diseases.
Mancozeb (Dithane T and O) is labeled for christmas cactus and may
also aid in disease control. Reduction of water applications greatly
reduces spread of the pathogen to aerial portions of the plants,
thus reducing disease severity.
rot on Easter cactus and Cereus
Pathogen - Drechslera cactivora
Symptoms - Blackened, sunken lesions from 1/16 to 1/2 inch
across form anywhere on the above ground portions of the plant.
The spots on holiday cacti are generally circular and can occur
below ground. Cladophyll abscission is common on plants even when
infection appears light. The black spores of the fungus form in
the spots, giving them a fuzzy appearance. The disease was first
described in the mid 1950's on Cereus and remains a problem for
some producers today. A rapid rot of the cotyledons of young cacti
is one of the first symptoms. Older plants become rotted where spines
have broken or the stem has been punctured. Most plants become blackened
and may be mush or dryish with collapse of the affected portion.
Rhipsalidopsis is very susceptible to Drechslera leaf spot and Schlumbergera
is moderately susceptible. Helminthosporium infects a number of
cacti and succulents in addition to Cereus and the holiday cacti.
Control - Use the same cultural controls as listed for soft
rot. In addition, sprays and drenches of chlorothalonil (Daconil
2787 formulations) are very effective in controlling the disease
but should be used with caution since it has been shown to cause
slight chlorosis occasionally. Mancozeb (Dithane T and O) is labeled
for some plants and may also aid in disease control.
root rot on Easter cactus
Pathogen - Pythium spp.
Symptoms - Foliage of plants infected with Pythium spp. turns
a dull gray-green and may wilt. Stems become rotted at the soil
line and upper portions of the plant collapse. Cladophyll abscission
may occur. Roots are darkened and mushy and generally sparse.
Control - Use pathogen-free pots and potting media and grow
plants on raised benches. Over watering plants may predispose them
to attack by root-rotting fungi. Soil drenches with the combination
of etridiazol and thiophanate methyl (Banrot), etridiazol (Truban
and Terrazole formulations) or metalaxyl (Subdue 2E) each are labeled
for some cacti and succulents and aid in control. Most cacti and
succulents can be infected with Pythium spp. if they are over watered
or planted in poorly draining potting medium.
rot on Easter cactus and Hawarthia
Pathogen - Erwinia spp.
Symptoms - A blackened, wet, slimy spot generally starts
at the soil line at the base of the plant and progresses into the
top of the cladophyll or into the upper portions of the plant. Plants
wilt, collapse and often die. Due to production of a special enzyme,
infected plants become very mushy and disintegrate especially during
the warmer months of the year.
Control - Remove and destroy infected plants as soon as they
are found. Keep watering to a minimum and avoid splashing since
this can spread the bacterium to other plants. Irrigate early in
the day to allow rapid drying of the foliage which reduces the ability
of the bacterium to infect. Be sure to obtain an accurate diagnosis
of the problem since several of the diseases caused by fungi appear
similar. Use of bactericides on plants infected with Erwinia spp.
is rarely effective. Most cacti and succulents will die if infected
with Erwinia spp. so prevention is the key to control.