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The Asian Citrus Leaf Miner

 

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How To Prevent Citrus Tree Leaf Drop Citrus Trees By: Amy Grant.


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


Environmental Causes of Citrus Leaf Problems Cold damage and improper watering, namely watering too much, are common environmental conditions that may lead to leaf drop on Citrus plants.


Cold damage – Citrus trees in general do not like cold or freezing temperatures. Hardier varieties are available, but cold damage, such as Citrus 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.

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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 Citrus tree winter leaf drop. Over watering – If your Citrus tree is dropping leaves, another common reason may be over watering

(which is almost imposable in the summer in Arizona – Warner- see the download IRRIGATING CITRUS TREES ).

When roots of the tree sit in water, they tend to develop root rot, which in turn results in the Citrus 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 Citrus 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 Citrus tree leaf drop. Depletions of nitrogen, magnesium, iron, zinc and manganese may all play a hand in causing Citrus 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.


Citrus Leaf Diseases Some Citrus 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.

Dependent 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 Citrus Leaf Problems A number of pests may also be responsible for Citrus 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 Citrus 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. In Florida the Introduction of a predatory wasp has also been a successful suppressor of the leaf miner.

Arriving here in 2011 and breeding up to 15 times a year, the Asian Citrus Leaf Miner was in every citrus tree I looked at for several years.

The population grew unchecked well into the summer of 2019,. So for at least 8 years, the leaves on your citrus trees have been producing far less energy than normal.

Because of this the reserve cells are dangerously low. Biologically speaking, your citrus trees have run out of gas.

Because it has no natural predator in Arizona there was nothing to keep it in check. However now it competes with the Ash Whitefly.

It takes years but eventually a citrus trees reserves will be drained to the point that it can no longer defend itself against any insects or soil born fungus.

That’s where we come in, if it’s not too late we can get you started on a program to restore the energy reserves of your trees.

Watch the videos on this page to learn more.

I hope you found this page about Tree Diseases in Mesa AZ useful. If you have any questions about Tree Disease please contact our Tree Service to schedule an appointment. We have been treating sick trees for over 50 years. We currently serve, Mesa AZ, Gilbert AZ, Chandler AZ, Scottsdale, Phoenix AZ and all of Maricopa County AZ.

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