Why Are My Limes Turning Yellow & Falling Off the Tree?

If your limes mature into a yellow color rather than the expected lime green, it doesn't necessarily mean that the fruit is diseased. Many fruit trees shed fruit naturally, so some fruit drop is normal, but if your lime tree (‌Citrus‌ spp.) should have green fruit and the fruit drop is excessive, you have a problem.

Can Limes Be Yellow?

There are two primary species of lime: Persian lime (‌Citrus‌ x ‌latifolia‌, USDA zones 9 to 11), also called Tahiti lime or Bearss lime, and Mexican (‌Citrus‌ x ‌aurantifolia‌, zones 10 to 11), or key lime. As a more cold-hardy variety, Persian lime is more often planted in the U.S.

Both produce pale yellow limes if the fruit is allowed to stay on the tree.

Limes are usually harvested when unripe to take advantage of their intense sour flavor at this stage. If you leave your limes on the tree too long, they will naturally turn yellow. Then, they will drop to the ground if you don't harvest them. If they don't appear diseased and have not yet rotted, go ahead and bring them into the kitchen and enjoy them!

‌Preventing the dropping of yellow limes if it is for natural reasons is simple: Harvest the limes sooner.‌ However, it's also possible that your limes are responding to environmental changes or have succumbed to disease or pests.

For example, thin-skinned citrus varieties, of which the Mexican lime is one, can become sunburned. A sunburned fruit develops a yellow shine on the area of sun exposure and results in an overly dry fruit—not only the peel, but also the pulp inside.

What Causes Citrus Fruit Drop?

Citrus fruit drop is common, according to the University of Maryland Extension. Not only is it common, it's normal for a tree to shed up to 75 percent of its fruit. If a tree has set far more fruit than it can support—more likely if the tree is growing in a container—it naturally drops the excess fruit in order to produce a healthy crop., but sometimes a citrus tree, including a lime tree, drops fruit due to other reasons.

Several variables are at play, so it's tough to determine the exact cause, reports the University of Florida IFAS Extension.

Environmental Stress

Citrus can become stressed by overly hot, humid weather, especially in the fall, causing fruit to drop. While you can't control the weather, you can monitor water uptake to ensure proper irrigation. Poor drainage can exacerbate fruit drop.

Alternaria Brown Spot

The next, most common cause of leaf and fruit drop is Alternaria brown spot, a fungal disease that first darkens the leaf veins and then develops brownish spots surrounded by yellow "halos" on the fruit.

Prevent this disease by choosing resistant cultivars, if possible. Ensure proper spacing between trees, or prune the tree if it becomes very bushy with a tight canopy. Apply copper fungicide in the spring at the first leaf flush and again after petal fall. You may also need to schedule additional applications throughout the growing season every two to four weeks.