Lime trees are bright, attractive trees that bloom and grow during summer, and go dormant during winter. Lime trees require full sun all day, good drainage, rich, loose soil and plenty of water. Like all citrus trees, limes have wood, fruit and leaves that both attract and are vulnerable to fungus and decay. When a lime tree is diseased, there are some serious repercussions for the tree's growth and fruiting abilities. Lime fungus can be both treated and prevented with careful use of fungicide.
According to Master Gardener Online, excess water and humidity bring on fungus on a citrus tree's leaves, bark and fruit. Since most fungus is soil borne, lawn grass and other low-lying plants can carry it to the base of a lime tree and subject the lime's wood to the fungal spores. Mulch carries decay and fungus, and also creates a moist, humid environment as it breaks down. Mulching the base of a lime tree encourages fungal growth and spread.
Types of Disease
Specific citrus diseases include citrus canker bacterial infection, melanose fungal infection, greasy spot fungal infection, sooty mold fungal infection and root rot fungal infection. Although the diseases are all similarly soil borne, they display some different symptoms on the tree, and damage the tree on different levels.
Citrus canker causes scabs on fruit, leaves and twigs, and leads to blemished fruit and leaf drops. Melanose affects the wood of the tree, while greasy spot and sooty mold cause blisters and blackening of the leaves, respectively. Root rot causes hard brown spots on the wood, leading to bark rooting and eventual death.
Treatment and Prevention
Fungi are generally treated with sprays of liquid copper fungicide and bug buster insecticide. June and July applications of the same may prevent the onslaught of fungal infections. Quantity and application of fungicides depends on the size of the tree and seriousness of the infection, and should always follow manufacturer directions.
To prevent fungus as much as possible, it's important to grow lime trees in isolated situations. Don't use sprinklers, which may get water on the tree's wood and leaves, and make it more vulnerable to fungus and mold growth. Keep lawn grass away from the base of the trees, and never use mulch for soil moisture or warmth.