Lemon Tree Dropping Leaves: How To Prevent Lemon Tree Leaf Drop

Lemon Tree Dropping Leaves: How To Prevent Lemon Tree Leaf Drop

Citrus trees are susceptible to a plethora of problems caused by pests, diseases and nutritional deficiencies, not to mention environmental stressors. Causes of lemon leaf problems are in the realm of “all of the above.” As with most leaf drop in citrus, treatment of leaf loss in lemons means narrowing the field of possibilities.

Environmental Causes of Lemon Leaf Problems

Cold damage and improper watering, namely watering too much, are common environmental conditions that may lead to leaf drop on lemon plants.

Cold damage – Citrus trees in general do not like cold or freezing temperatures. Hardier varieties are available, but cold damage, such as lemon tree winter leaf drop, is likely when temps drop to 28 F. (-2 C.) for four hours or longer. If temps drop below 32 degrees F. (0 C.), it’s best to protect young trees (under five years) by covering them or moving to a protected area. Water the plant, if possible, 48 hours prior to the freeze and postpone pruning until spring since newly pruned trees are more susceptible to prevent lemon tree winter leaf drop.

Over watering – If your lemon tree is dropping leaves, another common reason may be over watering. When roots of the tree sit in water, they have a tendency to develop root rot, which in turn results in the lemon tree dropping leaves. Mulch around the root area, minimize irrigation, plant in well draining soil and keep grass away from the base of the tree to avoid root rot and its accompanying problems.

Nutritional Deficiencies Causing Lemon Tree Leaf Drop

Sixteen nutrients are necessary for the growth of plants and trees, and depletion of any one of these may cause serious issues such as lemon tree leaf drop. Depletions of nitrogen, magnesium, iron, zinc and manganese may all play a hand in causing lemon tree leaf drop as well as reduction in size and general production of fruit.

To maintain healthy trees, fertilize citrus every six weeks when the tree is under seven years old with a good citrus fertilizer — not fertilizer tree spikes. Adult trees should be fertilized often but in small amounts from October through February.

Lemon Leaf Diseases

Some lemon leaf diseases that result in yellowing, dieback and defoliation are: alternaria brown spot, greasy spot, and phytophthora.

Alternaria leaf spot – Alternaria brown spot not only yellows leaves, but produces blackening of leaf veins with fruit that has sunken black to brown spots with yellow halos, resulting in fruit drop. Disease resistant varieties should be planted and spaced apart to promote rapid drying of the canopy.

Copper fungicides can be sprayed when the spring flush leaves are half expanded and then again when fully open. Another spray should occur four weeks later. Dependant on the amount of spring precipitation, applications should be done every two to four weeks from April through June.

Greasy spot fungus – The fungal spores of greasy spot fungus first appear as yellow spots on the top side of the leaf, becoming oddly shaped brown blisters with a greasy appearance on lower and upper surfaces. Leaf drop decreases fruit set and increases the chance of damage to the tree from cold or pests.

Again, spraying with a copper fungicide, being sure to cover the underside of the leaves, will aid in eradicating the disease. Spray for the first time in May to June and then spray again in July to August.

Phytophthora – Phytophthora is a soil borne pathogen that causes root rot and foot rot while also afflicting the leaves, causing leaf drop, fruit drop, dieback and finally death.

Improving drainage and irrigating in the morning will aid in elimination of phytophthora as will keeping the area around the tree free from grass, weeds, other debris and mulch.

Other Causes of Lemon Leaf Problems

A number of pests may also be responsible for lemon tree leaf drop. Asian citrus psyllid produces honeydew, which leads to sooty mold as well as causing damage and leaf drop due to the feeding on of the young citrus leaves. Oil sprays can control this pest when applied frequently.

Citrus leaf miners are also an intrepid pest assailing lemon tree leaves. Barely noticeable to the naked eye, leaf miners are not easy to control with chemicals since they are burrowed into their dens between leaf and stem. Infected areas of the tree should be removed and destroyed to aid in management of the insects. Introduction of a predatory wasp has also been seen as a successful suppressor of the leaf miner population.

About Meyer Lemon Tree Diseases

The Meyer lemon originated in China and was brought to the United States in 1908. It is not a true lemon and it is much less acidic than that of a regular lemon. The juice of the Meyer lemon is used as a substitute for regular lemon juice, but it looks has a very distinctive appearance. It resembles a large orange in both shape and color. The Meyer lemon, like other lemons, is susceptible to the same diseases as other citrus fruits.

Identifying and Treating Lemon Tree Diseases

The lemon tree is perhaps the most popular of citrus fruit trees cultivated the world over. Diseases that attack this tree may be viral, bacterial or fungal in nature. Most of them are not fatal. However, it helps to recognize symptoms early and take appropriate action. You can ensure the continued good health of your tree if you maintain a keen eye for any disease outbreaks. Following is a guide to help you identify and manage lemon tree diseases.

Citrus Canker

This bacterial disease causes leaves and fruit to drop off prematurely. Holes develop on the leaves which gradually turn brown. The fruit also becomes brown and develops bumpy areas with a water-soaked or oily yellow margin. Although the tree is unlikely to die, citrus canker causes a significant decline in health. Fruit yields are reduced and affected trees eventually cease to produce any fruit. Citrus canker is a highly contagious disease. Sharing garden equipment, severe storms and strong winds are likely to spread the infection rapidly. Spray with a copper fungicide immediately you notice the canker. However, trees that are severely infected need to be uprooted and destroyed.

Yellow Dragon Disease

It is a bacterial disease mainly spread by insects. Infected trees become yellow and weak. Leaves may become mottled. Fruit remains small and looses shape. Quite often ripened fruit will retain some green color. Uproot and dispose of any infected trees as this is the most effective way of control.

Brown Rot

Also known as root rot, this is a fungal disease caused when spores from the ground attack the trunk. It spreads more rapidly during severe storms. Brown patches of toughened bark develop on the tree trunk. Sap may ooze from the infected area. Mature fruit develop brown lesions with a strong odor. Foliage and blossoms also turn brown and decay. Gather and dispose of all infected leaves and fruit as they fall off the tree. Cut off low-hanging branches to help check the spread. Use a copper fungicide to spray affected parts immediately you notice symptoms. Repeat spray application after two seasons.

Greasy Spot

This is a fungal infection. Decomposing leaves on the ground underneath the tree develop airborne spores. These reproduce and transfer onto the tree through lower leaf surfaces. After an incubation period of several months black spots develop on the leaves. The tree experiences leaf loss which increases with time. Greasy spot is encouraged by warm and damp conditions. Gather and dispose of all fallen leaves. Spray with a liquid copper fungicide once in the summer and repeat in the fall.

Citrus Tristeza

This viral infection is spread by aphids. Grafting trees on vulnerable rootstock is likely to encourage the disease. Citrus tristeza causes wilting of trees, leaves become yellow and curly, and the tree remains dwarf-sized. Fruit yields also decline. It can be fatal if it causes a blockage of the circulatory system, leading to the death of the tree. Prevention is the best strategy in managing citrus tristeza. Choose healthy rootstock that can withstand the disease. Otherwise, spray infected trees with an insecticide to eliminate the aphids. This will help contain the spread of the disease.

Too Much Fertilization

Excessive fertilizer can lead to leaf drop. Young trees require light fertilization during the first year about 1 tablespoon per month during spring and summer. Beyond the first year, fertilize trees once every four to six weeks and gradually increase the amount of fertilizer each year as the tree grows, using a fertilizer made for citrus or an 8-8-8 fertilizer.

When using fertilizer, make sure you sprinkle it evenly, covering the entire root zone. Do not pile fertilizer right at the tree base, as this can cause damage. Proper fertilization practice can help prevent leaves falling off Meyer lemon trees from over-fertilization.

Lemon Leaf Problems - What Causes Lemon Leaves To Drop Off - garden

Low light levels area common reason for leaf drop and sometimes shoots may die back. The plant should be placed in a position where it receives the brightest light. Any shoots that have died should be pruned back to healthy wood.

Sudden temperature changes or low temperatures can result in the loss of leaves. This is more likely to occur in winter.

Care should be taken to avoid over or under watering as this will lead to leaf loss. An over wet compost will also result in the roots rotting. In winter water the plants well and allow the compost to dry out before watering again. As temperatures start to rise in spring and new growth appears increase watering to keep the compost moist.

Indoors a dry atmosphere can result in leaf drop, misting with tepid water and standing the pot in a saucer containing gravel and water will increase the humidity around the plant. Ensure the pot is not standing in water as this will cause the roots to rot.

Citrus trees should never be stood near a radiator or other heat source. The trees like good air movement and when conditions are favourable and temperatures start to rise ventilate the greenhouse or conservatory on warm sunny days.

Potting the plant in a container that is too large can put the plant under stress and will also reduce the number of fruit produced.

Scale insect are a common pest of citrus trees and can be found on stems and both upper and lower leaf surfaces often next to leaf veins. Scale insects can be flat or domed and brown or greyish white in colour. Severe attacks can result in leaf drop. Spray the plant with an appropriate insecticide.

What's Wrong With My Meyer Lemon?

Lots of people must be growing Meyer lemon trees indoors, because lots of people keep asking Grumpy what the heck is wrong with theirs. If you're one of them, console yourself with the thought that these citrus trees are notoriously finicky and often drive their owners nuts. Here's a list of common complaints and what you can do about them.

But first, let's review what these trees require in order to grow well in a pot. They need very bright light, excellent drainage, mild temperatures, and proper fertilization with a fertilizer formulated just for citrus that contains iron, zinc, manganese, and magnesium. Leave out just one of these things and your tree will not be happy.

OK, these are the complaints Grumpy hears most often and actions you should take to keep them from happening again.

"Most of the fruit drops off while it's still small." It's natural for a Meyer lemon to do this, because it often sets much more fruit than it can ripen. (Remember, it's growing in a pot, not in the ground.) Other possible causes -- too much fertilizer at the wrong time (use citrus fertilizer at the rate recommended on the label in spring or summer when the tree is actively growing) soil got too dry after fruit set.

"Most of the flowers fall off before setting fruit." Meyer lemon often does this as a way to prevent setting too much fruit. Other possible causes -- fertilizing at the wrong time soil got too dry soil stayed too wet tree was exposed to cold temperatures.

"Lots of leaves turn yellow and drop at the same time." Something is wrong with the soil. Most often, it's that the roots are staying wet too long. This leads to root rot, leaf drop, and possible death. Citrus trees should NEVER sit in saucer filled with water. When you water, do so thoroughly so that excess water runs out of the drainage hole. Then let the soil go somewhat dry before watering again. Other possible causes -- nutrient deficiencies due to lack of fertilization exposure to cold poor drainage and wet soil.

"The lemons stay green and don't ripen." Meyer lemon doesn't ripen like an apple. The process takes a long time. Often the fruit will reach full size and stay green for months before it changes color. So be patient. Other possible causes -- lack of sun your kids painted the fruits green for a school project.

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