May 3, 2015

Pests and Disease Management in Lemon and Citrus


http://www.dpi.nsw.gov.au/__data/assets/image/0006/138912/citrus-aphids.jpgption

Disease
Symptoms
Cause
Comments
Management
Anthracnose
(Colletotrichum gloeospioides)
Premature leaf drop, dark staining of fruit, dieback of twigs, leaves and twigs covered in dark spores
Fungus
Disease common during wet season
Appropriate fungicide application is required
Mal secco
(Phoma tracheiphila)
Chlorosis  of leaf veins, leaves may have red discoloration,  infected bark may turn silver-grey in color
Fungus
A major problem for citrus growing areas in Mediterranean
In infected trees diseased shoots and branches should be pruned early, trees can be prevented by spraying copper fungicides
Citrus canker
(Xanthomonas  axonopodis)
Raised lesions on leaves, often at leaf margin or tip
Bacterium
Bacteria may enter through pruning wounds, mainly due to wind driven rain
 All infected areas should be removed, wind breaks can help to reduce severity
Bacterial canker
(Pseudomonas  syringae)
Cankers on twigs and branches, twigs may be girdles and die, leaves turning black and dying
Bacterium
Symptoms severe on south facing side of tree exposed to winds
Copper fungicide recommended in fall and winter prior to the first rains
Tristeza Disease
(Citrus tristeza virus - CTV )
Poor new growth, young trees blooming early, light green foliage, severely affected tress are stunted bushy in appearance
Virus
Disease spread by infected grafting material or aphid
Quarantine procedures are used to control tristeza and prevent the pathogen from entering areas which are currently from disease
Citrus leaf miner
(Phyllocnistis citrella)
Heavy infestation can cause curled and distorted leaves, adult leaf miner is a tiny moth which lays its eggs in the leaf, larvae hatch and feed on interior
Insect
Leaf  miner attack the flushes of young growth and are unable to enter leaves once they harden
Insecticide and pesticide applications are recommended
Soft scales ( Black scale, soft scale, citricolla scale)
Reduced tree vigor, leaves covered with sticky substances and may have growth of sooty mold
Insects
Insects can produce several overlapping generations per year
Organic methods of control include the application of horticultural oils and preservation of natural enemies
Thrips
(Scirtothrips citri)
Insects feeds under sepals of young fruit and causes a ring of scarred tissue as the ring expands
Insect
 Insects overwinter on trees as eggs and can undergo multiple generations per year
Insecticide application is rarely requires as healthy trees can withstand heavy feeding damage
Black root rot
(Thielaviopsis  basicola)
Small brown lesions on roots which may coalesce and turn entire root black
Fungus
Serious disease of glasshouse grown citrus trees, pathogen usually drops to non-damaging level after tree is transplanted to the field
Keep glasshouses
Well lit and warm during winter to encourage vigorous  root growth, use quality potting soil
Aphids ( Black Citrus Aphid )
Leaves curling, leaves and twigs covered with sticky substance, insects are small and soft bodied and are black in color
Insects
Aphids transmits tristeza  virus on citrus
Aphid population tend to naturally decline as leaves harden off but can be a problem on young trees

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Pests and Disease Management in Lemon and Citrus
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Oleh