Symptom | First noticeable | Primary cause | Occurs | Control and/or comments |
---|---|---|---|---|
Fruit | ||||
1. Premature rind coloring | late summer | plant bugs | mid-summer | Rarely serious enough to control |
2. Creases in rind | harvest | physiological | spring | Follow irrigation and fertilization recommendations |
3. Necrotic spots on rind, lower part | 2 or 3 weeks after spraying | spray burn | after spraying | Excess spray accumulates near bottom of fruit |
4. Thick rind, puffy fruit, sheepnose | harvest | excess vigor | since bloom | Follow good cultural practices, typical of off-bloom fruit |
5. Rust colored or brown rind | anytime | citrus rust mite | since bloom | Does not affect eating quality, use miticide only if necessary |
6. Silvery to tan irregular, smooth blemishes | harvest | wind scar | March-April | Not necessary, quality unaffected |
7. Small, brown spots on rind, rough texture, may tearstreak | harvest | melanose fungus | March-April | Affects grapefruit only, remove dead twigs inside canopy |
8. Removable, small, colored, raised spots on rind | summer to harvest | scale insects | summer | Spray only if problem is extensive on the bark |
9. Cottony masses near fruit stem | summer to harvest | mealybug or cottony cushion scale | summer | Rarely serious, hard to control |
10. Black, sooty covering | harvest | sooty mold | since bloom | Whiteflies, blackflies, mealybugs and other insects, usually gone before problem is noticed |
11. Fruit drop | since bloom | physiological | since bloom | Read “Productivity and Maturity” section |
12. Fruit splitting on-tree | September | physiological | summer | Dry weather followed by good rain, proper irrigation lessens the problem |
Leaves and twigs | ||||
1. Leaf cupping and curling | after new flush | aphids | during each flush | Not serious, check new growth as it emerges |
2. Silvery, scratchy appearance to leaf | summer, fall | spider mites | spring to fall | Could cause excessive fall leaf drop, spray if necessary |
3. Small, brown spots, sand-papery texture | spring-summer | melanose fungus | after growth flush | Affects grapefruit, usually after spring rains; remove dead twigs |
4. Irregular, oily spots on foliage | summer to winter | greasy spot fungus | summer | Remove fallen leaves, particularly in summer |
5. Raised, irregular tar-like spots underleaf | anytime | sunburn | anytime | Not serious |
6. Removable, small, colored spots on leaves or bark | anytime | scale insects | summer | Spray only if infestation is extensive |
7. Fish-scale-like scales underleaf, translucent; small, white, flying insects | spring to fall | whiteflies | spring to fall | Leads to sooty mold; rarely requires control |
8. Spirals of eggs or small black insects underleaf | anytime | blackfly | anytime | Leads to sooty mold; insecticides do not work, parasites normally in control |
9. Black sooty coverings on leaves | anytime | sooty mold | anytime | Control causal insects or wash off with soapy water |
10. Leaf yellowing, drop and twig dieback | anytime | root damage | anytime | Usually too much water, poor drainage |
11. Leaf yellowing, tipburn marginal necrosis, drop | anytime | salt burn | anytime | Leach soil, be careful with fertilizer |
12. Leaf yellowing, yellow area confined to veins | anytime | foot rot, water damage | anytime | Determine cause and correct, if possible |
13. Marginal necrosis, leaf cupping, curling | spring flush | wind burn | during spring flush | Usually not serious, windbreaks may help |
Limbs, trunk or entire tree | ||||
1. Tree looks sick, sparse, yellow-veined foliage, dead bark on trunk near ground | anytime | foot rot | anytime | Remove dead tissues, disinfect and treat with pruning paint; follow recommended cultural practices |
2. Hardened gum exudate on bark of trunk or limbs | anytime | gummosis | anytime | Follow good cultural practices, no control, not usually life-threatening |
3. Young tree seemingly loses all its leaves quickly, fruit hangs on | anytime | foot rot | anytime | Check for foot rot (dead bark) completely around trunk at and above the bud union |