PLANT PATHOLOGY:
DIAGNOSTIC KEY [continued]
Previous
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MG
Manual Reference
Ch. 4, pp. 23 - 24 |
[ 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 FRUIT TREES
STONE FRUITS 
| SYMPTOMS |
CAUSES |
CONTROLS |
| Swellings and abnormal growths present on
roots and/or trunk at or just below ground level; trees appear
stunted and lack vigor |
• Crown gall (bacterial disease) |
• Chemical controls have not been
effective; if this disease has been a problem in the past,
replant with resistant species |
| Purple spots appear on upper
surfaces of cherry leaves; leaves develop holes and turn yellow;
fruit may also be spotted |
• Cherry leaf spot (fungal disease) |
• Resistant cherry varieties include
Meteor and Northstar; use registered fungicide spray |
| • Shothole fungus |
• Use registered fungicide spray |
| Gum oozes from holes at base of trunk or lower
branch crotches; sawdust may be evident |
• Peach tree borer |
• Use paradichlorobenzene (moth) crystals
around base of tree; use registered insecticide on bark only;
monitor with pheromone traps |
| Blossoms and young twigs wilt and decay during
bloom; sunken cankers may develop on twigs; circular brown spots
which develop tufts of gray spores during moist weather form on
fruit |
• Brown rot (fungal disease) |
• Remove all affected fruit on tree and
on ground; prune out any twig cankers |
| Many small round holes in twigs and branches |
• Shothole borer |
• Remove and destroy all dead or dying
wood |
| Sunken, distorted areas on fruit, cat-facing |
• Various plant bugs |
• Control weeds and brushy areas around
fruit trees |
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CITRUS
| SYMPTOMS |
CAUSES |
CONTROLS |
| Poor fruit development (small
number of fruit on tree) |
• Biennial bearing |
• Older citrus trees tend to become
alternate bearers |
| • Frost injury |
• Frost recovery triggers more vegetative
growth and less fruit |
| Young leaves curled and distorted; clusters of
insects on undersides of leaves |
• Thrips |
• Does only cosmetic damage; no control
needed |
| Fruits splitting in the fall |
• Heat, water stress
• Sun |
• Heat, water stress |
| Peeling bark and gumming near soil line |
• Fungal disease |
• Pull soil away from trunk; keep water
from touching trunk; clean off the infected bark and treat with
Bordeaux as a paste |
| Gumming up the trunk or on major branches of
grapefruit |
• Rio Grande gummosis |
• Not a disease, simply a symptom of old
age on grapefruit; no treatment needed |
| Fruits with single small hole; the fruits
filled with beetles and flies |
• Bird damage |
• Scare birds away or use netting;
neither is too effective; the insects are a secondary problem |
| Navel oranges black at the flower end and down
the core |
• Alternaria (fungal disease) |
• No control; disease is worse during
certain weather conditions |
| Few fruits on navel orange |
• Heat stress |
• Navels are extremely sensitive to heat
and at first heat of summer most of the fruits may fall off |
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