Table 2. Diagnosis of common citrus problems.

SymptomFirst noticeablePrimary causeOccursControl and/or comments
1. Premature rind coloringlate summerplant bugsmid-summerRarely serious enough to control
2. Creases in rindharvestphysiologicalspringFollow irrigation and fertilization recommendations
3. Necrotic spots on rind, lower part2 or 3 weeks after sprayingspray burnafter sprayingExcess spray accumulates near bottom of fruit
4. Thick rind, puffy fruit, sheepnoseharvestexcess vigorsince bloomFollow good cultural practices, typical of off-bloom fruit
5. Rust colored or brown rindanytimecitrus rust mitesince bloomDoes not affect eating quality, use miticide only if necessary
6. Silvery to tan irregular, smooth blemishesharvestwind scarMarch-AprilNot necessary, quality unaffected
7. Small, brown spots on rind, rough texture, may tearstreakharvestmelanose fungusMarch-AprilAffects grapefruit only, remove dead twigs inside canopy
8. Removable, small, colored, raised spots on rindsummer to harvestscale insectssummerSpray only if problem is extensive on the bark
9. Cottony masses near fruit stemsummer to harvestmealybug or cottony cushion scalesummerRarely serious, hard to control
10. Black, sooty coveringharvestsooty moldsince bloomWhiteflies, blackflies, mealybugs and other insects, usually gone before problem is noticed
11. Fruit dropsince bloomphysiologicalsince bloomRead "Productivity and Maturity" section
12. Fruit splitting on-treeSeptemberphysiologicalsummerDry weather followed by good rain, proper irrigation lessens the problem
Leaves and twigs
1. Leaf cupping and curlingafter new flushaphidsduring each flushNot serious, check new growth as it emerges
2. Silvery, scratchy appearance to leafsummer, fallspider mitesspring to fallCould cause excessive fall leaf drop, spray if necessary
3. Small, brown spots, sand-papery texturespring-summermelanose fungusafter growth flushAffects grapefruit, usually after spring rains; remove dead twigs
4. Irregular, oily spots on foliagesummer to wintergreasy spot fungussummerRemove fallen leaves, particularly in summer
5. Raised, irregular tar-like spots underleafanytimesunburnanytimeNot serious
6. Removable, small, colored spots on leaves or barkanytimescale insectssummerSpray only if infestation is extensive
7. Fish-scale-like scales underleaf, translucent; small, white, flying insectsspring to fallwhitefliesspring to fallLeads to sooty mold; rarely requires control
8. Spirals of eggs or small black insects underleafanytimeblackflyanytimeLeads to sooty mold; insecticides do not work, parasites normally in control
9. Black sooty coverings on leavesanytimesooty moldanytimeControl causal insects or wash off with soapy water
10. Leaf yellowing, drop and twig diebackanytimeroot damageanytimeUsually too much water, poor drainage
11. Leaf yellowing, tipburn marginal necrosis, dropanytimesalt burnanytimeLeach soil, be careful with fertilizer
12. Leaf yellowing, yellow area confined to veinsanytimefoot rot, water damageanytimeDetermine cause and correct, if possible
13. Marginal necrosis, leaf cupping, curlingspring flushwind burnduring spring flushUsually not serious, windbreaks may help
Limbs, trunk or entire tree
1. Tree looks sick, sparse, yellow-veined foliage, dead bark on trunk near groundanytimefoot rotanytimeRemove dead tissues, disinfect and treat with pruning paint; follow recommended cultural practices
2. Hardened gum exudate on bark of trunk or limbsanytimegummosisanytimeFollow good cultural practices, no control, not usually life-threatening
3. Young tree seemingly loses all its leaves quickly, fruit hangs on anytimefoot rotanytimeCheck for foot rot (dead bark) completely around trunk at and above the bud union

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