Pests and Disease Management in Lemon and Citrus
Bacterial canker Black Root Rot Citrus canker Pests and Disease Control in Lemon Soft scales Tristeza disease |
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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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