| Disease (causal agent) |
Symptoms |
Survival of pathogen and effect of environment |
Comments on control |
Bacterial soft rot
(Erwinia chrysanthemi) |
Soft, watery rot of leaves; often foul smelling. Starts
as small water-soaked area. Infection is through wounds. Often fatal. |
In soil and decaying plant debris. Bacteria spread in
water. Favored by warm, moist conditions. |
Avoid overhead watering, wounding plants, and provide
horizontal air movement and good aeration. Observe strict sanitation.
Disinfect knives between cuts. |
Black rot and seedling
damping-off
(Pythium ultimum, Phytophthora cactorum) |
Starts as small, water-soaked leaf spots and root rot.
Decay may progress rapidly. Affected tissues turn black and are sometimes
soft. |
Soilborne fungi. Spores spread in water. Favored by
warm moist conditions (above 65°F). |
Drench plants with mefenoxam. Steam or chemically treat
growing media and used pots. Remove badly infected plants. more info:
Pythium Root Rot, Phytophthora
Root and Crown Rots |
Botrytis flower brown speck or rot
(Botrytis cinerea) |
Tiny, light-brown spots on blossoms may enlarge to rot
entire flower. Woolly gray fungal spores develop on flowers if kept
moist. |
On plant debris. Spores airborne. Favored by cool, moist
conditions. |
Eliminate old flowers. Eliminate plant debris, both
inside and outside growing area. Avoid getting flowers wet. Treat
with fenhexamid. |
Gloeosporium leaf spot
(Gloeosporium spp.) |
Prominent, sunken, reddish brown spots with definite
margins. Spots may coalesce and kill entire leaf. Spots start as minute,
dark areas, often at leaf tips. |
In infected plants. Spores spread in water. Favored
by moist conditions and unfavorable growing conditions. |
Provide better growing conditions. Avoid wetting foliage.
Remove infected tissues. |
Rust
(Sphenospira sp.) |
Pustules of powdery, yellow or orange spores on undersides
of leaves. |
In infected plants. Spores airborne. Moisture needed
for only short period. Not too common. |
Avoid wetting leaves. Destroy infected leaves. more
info |
| |
| Virus or viruslike disease |
Symptoms |
Host range and natural spread |
Comments on control |
Blossom necrotic streak
(a strain of Cymbidium mosaic) |
Blossoms open without evidence of brown spots or streaks,
which become visible after about 1 week or longer. Long, yellowish,
irregular streaks may develop on leaves. |
Can be spread on cutting tools. |
Use clean cutting tools. Destroy infected plants. |
Leaf necrosis
(Cymbidium mosaic virus) |
Irregular, elongated streaks of dead tissue on undersurface
of older leaves. Some leaves may be killed or various patterns of
sunken, black tissue may develop. Infected plants may show no symptoms. |
Pruning tools. Cattleya and its hybrids, Cymbidium,
Epidendrum, Zygopetalum, Angraceum, Laelia, Oncidium, Spathoglottis. |
|
Mild flower break
(Odontoglossum ringspot virus) |
Flowers less variegated than above and without distortion.
Leaves show only mild, hard-to-detect mosaic symptoms. Spots and streaks
of increased pigment intensity. |
Unknown, but can be transmitted by juice inoculations.
Cattleya and its hybrids, Cymbidium, Odontoglossum, Phalaenopsis. |
Plants may be infected by more than one virus. All viral
diseases are propagated with plant. Once infected, plant remains so
for life. Isolate or destroy infected plants. Disinfect tools between
cuts with a quaternary ammonium disinfectant. |
| Severe flower break |
Variegation of flower color. May also distort sepals
and petals. Leaves mottled with streaks of light and dark green tissue.
Dark green areas somewhat raised, producing ridges and bumps. |
Green peach aphid. Cattleya and its hybrids,
Cymbidium. |
Same control for all viruses. |
| Symmetrical flower break |
A symmetrical variegation in which pigment occurs along
sepal margins and over most of petals, except in middle areas that
have little or no pigment. Leaves may develop an inconspicuous mosaic
mottle. |
Unknown, but can be transmitted by juice inoculations.
Cattleya. |
|
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