Title : Aphids in citrus
Visit Count : 1099 Time(s)
Upload Date : 3/10/2016 - 2 Year(s) ago
Category : citrus
Thursday, March 10, 2016
Visit Count : 1099 Time(s)
Upload Date : 3/10/2016 - 2 Year(s) ago
Category : citrus
Ten species of aphids) Aphis gossypii، Toxoptera aurantii، Aulacarthum solani، Aphis spiraecola، Aphis fabae، Aphis craccivora، Aphis nasturtii، Myzus persicae، Aphis rumicis، Macrosiphum euphorbiae (on citrus are recorded in Iran but only two are important in Citrus north Iran, Aphis gossypii and Aphis spiraecola Patch.
Like other sap-sucking insects such as mealybugs and scales, aphids produce a sticky substance (honeydew) as they feed on the plant.
A black fungus (sooty mould) grows on the honeydew, coating leaves, branches and fruit with a black powder. Aphids can be a threat to young trees, but are otherwise regarded as minor pests.
• All aphids have a piercing-sucking mouthpart (stylet) that they insert into the plant tissue to feed on leaves, green shoots and flowers. Leaves may curl as a result of feeding damage.
• Large quantities of honeydew are also produced as the aphid feeds. Leaves and fruit often turn black with the growth of the sooty mould fungus.
• Aphids are not usually a problem in citrus, except on young trees.
• Overseas, black citrus aphid has been associated with the spread of citrus tristeza virus which causes dieback.

Life cycle
• Females do not need to mate to produce young and no eggs are laid. Live young are produced through a process termed parthenogenesis.
• Female aphids are born pregnant and adult females can be wingless or winged.
• Winged forms indicate that the food quality has declined, or that there is overcrowding

Chemical control
• Natural enemies normally keep aphid populations under control. Chemical control is rarely required.
• Use a specific aphicide or horticultural spray oil.
• Always check the label before spraying, as not all oils are registered for use in citrus. Oils can also cause phytotoxic damage if not used correctly.
Biological control
• Predators, parasites, and fungal diseases all attack aphids and occur naturally in the orchard. The honeydew produced by the aphids provides a good food source for many natural enemies.
• Aphid parasites include the wasp genera Aphidius and Aphelinus: neither is available commercially. The female wasps lay their eggs individually inside the lower part of the abdomen of young nymphs. The parasitised nymphs appear bloated and bronze in colour.
• Aphids are attacked by many generalist predators include hoverfly larvae (syrphids), ladybird beetles and lacewing larvae.
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