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PLANT PATHOLOGY: DIAGNOSTIC KEY [continued]

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  MG Manual Reference
Ch. 4, pg. 30
[ 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

PINE Top

SYMPTOMS CAUSES CONTROLS
Black, sooty substance covers needles and stems • Sooty mold, a fungus very common on pine, grows on honeydew secreted by aphids and other insects • Control aphids with hard stream of soapy water or registered insecticide
Clusters of caterpillar like insects feeding on needles in groups • Sawflies • Use registered insecticide or dust with diatomaceous earth
Needles turn brown from tips of branches back • Dry soil • Water tree deeply
Infested tips, twigs, laterals and terminals turn straw color, brown, and shrivel up; needles fade and fall off, leaving a dry papery shell that was once a green shoot • Pine tip moth, especially on Pinus eldarica • Prune and destroy the infested shoots; if damage is severe, use pheromone traps to determine timing of insecticide sprays
Oldest needles turn yellow or brown throughout the tree • All pines naturally drop older needles • None needed
Needles take on a gray-green color that later turns reddish- brown; some twig and small branch death; branch cankers appear as water-soaked areas that turn brown and split open • Physiological disorder of Aleppo pine (Pinus halepenis) • Maintain a uniform deep water supply to the tree throughout the year; irrigate so that water is available to a depth of 5 feet for mature trees
Fading foliage high in the tree; needles change from green to light straw color within a few weeks; boring dust in bark crevices and at the tree base; small pitch tubes may be present • Bark beetles • Prune out dying or recently dead branches; dispose of susceptible wood, slash, and bark; treat weakened or damaged trees with registered insecticide, or remove trees.



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