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PLANT PATHOLOGY: DIAGNOSTIC KEY [continued]

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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 Top

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

ROSE Top

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  
• Waterlogged soil • Improve drainage

PALM Top

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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