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Ask a Master Gardener: Backyard Citrus: Know Before You Grow

By: Jack LeCroy, Regional Extension Agent & Jacob Kelley, Regional Extension Agent,

Many citrus trees full of bright fruit can be seen in our area this time of year. Some homeowners even have the “problem” of finding what to do with the bountiful harvests. Critical to making sure our trees continue to produce is keeping them healthy. Over the past few years, disease developments have severely impacted the citrus industry and homeowners’ citrus trees elsewhere. Two that citrus growers need to be aware of here are citrus canker and citrus greening.

Citrus greening can impact most citrus cultivars. It is thought to be caused by the bacterium Candidatus Liberibacter asiaticus. The Asian citrus psyllid insect is the vector for this bacterium. Early symptoms of this disease are asymmetrical yellowing on the leaf along with lopsided fruit. Infected trees or branches suffer heavy leaf drop followed by out-of-season flushing and flowering. Dieback occurs in severe cases. Currently, citrus greening has no cure but there are steps that you can take to try to keep your citrus tree healthy.

Scouting your tree and finding a correct diagnosis are essential. Conducting a soil test and fertilizing appropriately throughout the year is also key. Contact insecticides such as oils, soaps, and malathion can be used, but they must contact the insect pest that carries the disease to be effective. Increase the chance of short-term success with a soil-applied systemic insecticide containing imidacloprid used against the Asian citrus psyllid. Remember to always read the product label or call your local Extension office for more information.

The newest incurable citrus disease to grace South Alabama is citrus canker. This disease is caused by the bacterium Xanthomonas axonopodis pv. citri and can easily be spread during wind-driven storm events, lawnmowing, and other human interaction with plants. Most citrus varieties, including satsuma mandarins, lemons, and grapefruit, are susceptible to citrus canker. Early signs that a plant may have citrus canker are leaves speckled with water-soaked lesions that have a chlorotic or yellow halo. As the lesions mature, the center may appear to be raised and corky with a halo that is water-soaked and chlorotic. These lesions are usually visible on both sides of the leaf. Diseased fruit will have similar lesions that appear to be raised, corky, blister-like wounds with oily or water-soaked halos. As the disease progresses, defoliation, twig dieback, premature fruit drop, and general tree decline can occur until the tree is removed or succumbs to the disorder naturally.

Prevention of any disease is the best line of defense. Using wind breaks to reduce disease dispersal and timely sprays of copper-containing products in 10–14-day intervals can reduce the chance of infection. Applications should begin when fruit are ¾ of an inch in diameter and continue until late October for minimizing infection. Even with these preventive tactics in place, infection is still a possibility.

Citrus canker is a severe disease, causing irreparable damage to the citrus industry in Florida. This has led the Alabama Department of Agriculture and Industries (ADAI) and USDA to take action to protect our growing citrus industry in Alabama. We need your help to protect our local citrus industry. When purchasing citrus plants or fruit, keep it local, Alabama. Members of the community and landscape maintenance personnel can help scout for diseased citrus. Report any findings to your local Alabama Cooperative Extension office. ACES Mobile: (251)574-8445 and ACES Baldwin: (251)937-7176.

If you are blessed with a bountiful citrus harvest, check out Grow More, Give More at Give More – Alabama Cooperative Extension System ( for giving suggestions. You can also call The Food Pantry at Central in Mobile (251-432-0591) to schedule a time to bring your citrus donation ( ). They provide food to 650 families in our area in need each week.

Mottling symptoms caused by citrus greening. Florida Division of Plant Industry, Florida Department of Agriculture and Consumer Services,

Lopsided fruit caused by citrus greening. Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services,

Foliar lesions caused by citrus canker surrounded by bright yellow halo. Kassie Conner - ACES
Fruit lesions caused by citrus canker are raised and corky. Kassie Conner - ACES

Lesions caused by citrus black spot on fruit are small, round, and sunken with gray centers and dark margins. P. Barkley, Biological and Chemical Research Institute,

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