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 - Botrytis cinerea
Symptons- Botrytis leaf and blossom blight usually appear
on lower leaves of cuttings in contact with the potting medium.
The water-soaked spot may enlarge rapidly to encompass a large portion
of the leaf blade or even the entire cutting. The area dies and
turns dark brown to black with age. When night temperatures are
cool, day temperatures warm, and moisture conditions high, the pathogen
readily sporulates on both leaves and flowers, covering them with
grayish-green dusty masses of conidia.
Control- Controlling Botrytis blight of foliage plants is
particularly important during the winter months. Methods which improve
foliage drying and reduce moisture condensation on foliage during
the nights reduce the need for fungicide application. These include
fans to circulate the air and facilitate rapid leaf drying, and
heating and venting at sunset to reduce the amount of moisture in
the greenhouse air. On some crops, Botrytis spores are more likely
to become airborne and spread when the plants are handled. It may
be advisable to time fungicide applications directly following a
time when the plants are handled (such as during moving or trimming).
Chlorothalonil (Exotherm Termil), iprodione (Chipco 26019), and
vinclozolin (Ornalin) are labeled for Botrytis control on coleus.
Pathogen - Genetic variability in the plant
Symptons - Leaves develop yellow variegation that can be
mistaken for virus infections. Plants with these symptoms are usually
rare unlike those infected with a virus. Distortion can also occur.
The reddish-purple coloration on some leaves is not normal for this
Control - If the number of off-type plants is high, a new
source of plants should be found. Discard those that are found,
but don't miss the opportunity for developing a new selection of
the plant. This is one of the oldest ways for new plants to come
into the commercial trade.
- Corynespora cassiicola
Symptons - Leaf spots appear first as tiny sunken areas
which are slightly brown. These areas enlarge to about 1/2 inch
in diameter and darken with age. Leaf drop is common under optimal
conditions for disease expression. Similar symptoms are seen on
other plants such as Aeschynanthus, Columnea, Ficus, Nematanthus,
Salvia, and Saintpaulia.
Control - Use standard cultural controls for fungal leaf
spot disease. Minimize overhead watering or exposure to rainfall
which can splash spores to new plants and aid in the germination
process. Never use plants with spots for propagation since this
makes pathogen spread to the new crop very likely. Iprodione (Chipco
26019) is labeled and should aid in disease control.
Pathogen - Pseudomonas cichorii
Symptons - Spots are water-soaked and turn dark green to
black. They may have a yellow edge but this is not common on coleus.
Control - Avoid overhead watering as much as possible to
reduce conditions for infection and spread of the pathogen. Preventive
applications of a copper bactericide may reduce disease slightly
but none are labeled on coleus at this time. Many other hosts of
P. cichorii have been identified; chrysanthemum, ferns, ficus, geranium,
gerber daisy, and philodendron among others.
Pathogen - Meloidogyne spp.
Symptons - Galls occur on roots and the root system may be
drastically reduced; plant stunting and wilting occur when severe
infestations are present. This problem is more likely to occur in
the landscape than during production.
Control - It is a good idea to examine the roots of all plants
for knots and galls before purchasing. Use sterile soil and grow
plants off the ground if possible. Check nematicide labels for this
plant and application methods.