PLANT PATHOLOGY:
DIAGNOSTIC KEY [continued]
Previous
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MG
Manual Reference
Ch. 4, pp. 28 - 29 |
[ Diagnostic Key:
vegetables |
specific vegetables;
asparagus,
bean, beet,
carrot, cole
crops, corn,
cucurbits,
eggplant,
lettuce, onion,
pea, pepper,
potato, tomato
| tree fruits|
specific fruits;
apple,
stone, citrus
| ornamentals | specific ornamentals;
rose family,
rose,
palm,
pine ]
KEYS TO PROBLEMS ON SPECIFIC ORNAMENTALS
COTONEASTER, PYRACANTHA, AND OTHER
MEMBERS OF ROSE FAMILY 
| SYMPTOMS |
CAUSES |
CONTROLS |
| Individual twigs die back, turn black, and
have curved tips; sunken canker may be evident on wood |
• Fire blight (bacterial disease) |
• Prune out affected branches; if you do
not observe the blackening or curved tips, problem could be
drought or root rot; black that can be rubbed off is sooty mold |
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ROSE
| SYMPTOMS |
CAUSES |
CONTROLS |
| Plants wilt; lower leaves may turn
yellow |
• Dry soil |
• Supply water |
| • Root knot nematode |
• Check roots for knots; solar
pasteurization of soil; plant in another area |
| • Waterlogged soil |
• Improve drainage |
| • Transplant shock |
• Water regularly after transplanting |
| Flower buds fail to open; blooms are deformed
with brown streaks or spots on petals |
• Thrips |
• Use registered insecticide; damage will
decrease during summer |
| Various patterns of yellow and
green on leaves, including streaks, rings, vein clearing, or
blotches |
• Virus disease |
• Common on roses; these viruses mainly
enter through grafts and are not transmitted from plant to
plant; purchase healthy stock; maintain shrub vigor; not
necessary to remove shrub |
| • Nutrient deficiency |
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| • Waterlogged soil |
• Improve drainage |
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PALM
| SYMPTOMS |
CAUSES |
CONTROLS |
| New growth spikes are yellow- to-brown and
eventually die. Older fronds wilt, collapse and die. |
• Bud rot (fungal disease) |
• Remove and destroy all infected
portions; avoid sprinkling or other methods of watering that
splash water onto base of leaves; infected and susceptible palms
should be drenched with a copper fungicide as a protective,
preventative measure |
| Weakened structural strength of fronds |
• Nutritional deficiency, usually caused
by lack of micronutrients |
• Manganese helps the plants use the
other nutrients more efficiently; apply a micronutrient
fertilizer containing 2-4% manganese |
| Light brown tips on Queen Palm fronds |
• Heat and wind |
• Expect more of this symptom when
exposed to reflected heat (walls, parking lots, etc.) and high
winds |
| Dark brown edges, parts of fronds "missing"
on Queen Palm |
• Bud rot (fungal) |
• Treat with registered fungicides |
| Fronds emerge crinkled as an accordion bellows |
• Mechanical |
• Emerging frond encountered an
obstruction and crinkled up; usually grows out of it; no cure |
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