There are several varieties of lime: Mexican lime, also known as key lime; Tahiti lime, also known as Bearss lime and Persian lime; Rangpur lime and Palestine sweet lime. Lime trees are susceptible to the same diseases and infestations as other citrus trees. There can be problems with the fruit, leaves and twigs, as well as the trunk, limbs and sometimes the entire tree.
Lime trees are very cold-sensitive and will not survive freezing temperatures. Therefore, they need to be planted in temperate areas. The soil conditions also play a role in their survival. Lime trees will need to be planted in areas that have good site drainage. Problems can occur if they are planted in heavy clay or poorly drained sites. Soils high in caliche will cause nutritional deficiencies. Lime trees do well when planted in full sun.
Problems with Fruit
Several problems and diseases can affect the fruit of lime trees. Citrus rust mites can occur at any time. This pest causes the fruit to be rust-coloured or brown, but does not affect the quality of the fruit. To treat this condition, you can use miticide, if necessary. Mealybug, or cottony cushion scale, will show up as cottony masses near the fruit stem, and it occurs from summer through harvest. This condition is seldom serious and is hard to control. Fruit splitting while the fruit is on the tree can occur during September. This is due to dry weather followed by a good rain. Improvement in irrigation will lessen the problem.
Problems with Leaves & Twigs
There are also some lime tree diseases that affect leaves and twigs. An infestation of aphids will cause leaf curling and cupping. This is not a serious problem; just check new growth. Another infestation is spider mites. They will give the leaves a silvery, scratchy appearance. Spider mites can appear in summer and fall, and if they cause a lot of leaves to fall off the tree, the tree should be sprayed. Greasy spot fungus is another problem; you will notice irregular oily spots on the leaves, and this may occur from summer to winter. Remove the fallen leaves. Scale insects can also be a problem, and they will appear as removable, small, coloured spots on the leaves or bark. These insects can appear at any time; if the infestation is extensive, use a spray to get rid of them. Then there is blackfly. This will appear as spirals of eggs or small black insects on the underside of the leaves and can occur at any time. Insecticides do not work on blackfly, which leads to sooty mould.
Problems with Limbs & Trunk
Problems that can occur with the limbs and trunk of the tree include foot rot, gummosis and foot rot of young trees. Foot rot can happen at any time. The tree will look sick, and it will have sparse yellow-veined foliage. There will be dead bark on the trunk of the tree or on the ground near the tree. Remove any dead tissue, disinfect and treat with pruning paint. Gummosis can also happen at any time. There will be hardened gum exudate on the bark of the trunk or limbs of the tree. There is no control procedure for gummosis, and it does not usually threaten the life of the tree. Foot rot in young trees happens when a young tree suddenly loses all of its leaves quickly. The fruit will remain, but the leaves will drop. This can occur at any time. Check for evidence of foot rot around the trunk and above the bud union.
Stylar End Breakdown
The same pests and diseases that attack other citrus trees can attack the lime tree. Limes can also develop stylar end breakdown. This is a condition in which some juice vesicles rupture. The rupture of these juice vesicles causes the juice to collect at the blossom end of the fruit. The juice is very acidic and will break down the rind at this end. In order to lessen the problem, the fruit should be picked in the late morning or afternoon. It should not be picked when the fruit is wet.