Prevention, management tips offered for citrus disease found in Harris County

HOUSTON — Owners of citrus trees in Harris County should be on the lookout for carriers and symptoms of a disease recently discovered there, experts with the Texas A&M AgriLife Extension Service said.

Citrus greening was confirmed in a tree at a retail nursery south of Houston on July 16. The disease, which is spread by an insect called the Asian citrus psyllid, has no cure and eventually kills infected trees, according to AgriLife Extension horticulture specialist Monte Nesbitt of College Station.

An adult Asian citrus psyllid on a citrus leaf. The insect is responsible for citrus greening disease. (Texas A&M AgriLife photo by Monte Nesbitt)

An adult Asian citrus psyllid on a citrus leaf. The insect is responsible for citrus greening disease. (Texas A&M AgriLife photo by Monte Nesbitt)

Fruit from infected trees is bitter but poses no health problems to humans. The disease exists throughout the world; the first Texas find was near San Juan in early 2012.

Nesbitt said citrus tree owners who manage their trees with vigilance can help prevent the spread of citrus greening.

“If you have healthy trees today, you will keep them healthy if you keep psyllids off of them,” Nesbitt said. “It takes year-round monitoring and insecticide treatment if they are present.”

Citrus greening is a disease caused by a bacteria spread by its insect vector or carrier, the Asian citrus psyllid, an insect about the size of a toothpick tip. In the nymph stage, the slightly larger psyllid is yellow-orange, has bright red eyes and feeds on new growth where it secretes a white, stringy and waxy substance, according to AgriLife Extension experts. The adult psyllids have a distinctive 45 degree angle posture when present on citrus leaves.

Blotchy leaves may be an indication of citrus greening. (Texas A&M AgriLife photo by Monte Nesbitt)

Blotchy leaves may be an indication of citrus greening. (Texas A&M AgriLife photo by Monte Nesbitt)

An infected tree shows blotchy mottling and yellowing of leaves, the leaves may tend to grow in bunches and infected trees will become unthrifty with twig and branch die-back, Nesbitt said.

Fruit produced on diseased trees is stunted, remains green or partially green and may belopsided, he said. Fruit may fall from the tree prematurely.

This tree is in severe die back due to citrus greening. (Texas A&M AgriLife photo by Monte Nesbitt)

This tree is in severe die back due to citrus greening. (Texas A&M AgriLife photo by Monte Nesbitt)

For more information, contact the AgriLife Extension office in your county. A tipsheet, Citrus Greening E-264, is available free at http://bit.ly/citrusgreeningpub in English, Spanish and Vietnamese. A list of organic and traditional insecticides used to control psyllids is also available at county offices.

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