Pests and diseases
Mediterranean fruit fly is the most destructive pest. Mandarin varieties are particularly susceptible and growers must control this pest to achieve success. Lemons and grapefruit are less susceptible to fruit fly damage but can also be stung. Baiting and netting are the only way to combat this pest. Other pests are scales, aphids, crusader bugs, leaf miner, snails and whitefly.
Consult the Department of Agriculture and Food web article 'Citrus pests' for further information. Fungus diseases attacking citrus trees are collar rot (phytophthora) which girdles the trunk, and Armillaria root rot, which attacks and kills the roots of trees. Fruit rots caused by blue and green moulds are also often seen on fruit hanging in the tree canopy, particularly those that have rind damage caused by wind or insects.
Other disorders
Unfavourable weather causes considerable damage to citrus fruits. Excessive heat will cause heavy shedding of young fruits, and strong sun light conditions can lead to sunburn causing internal decline. When cut open, sunburnt fruit will be normal on one side but have brown pulp and dry flesh on the burnt side.
Fruit drop may be minimised with good management, such as adequate watering and mulching.