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 
| 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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