Citrus Greening Disease Discovered In The Florida Panhandle

 

Tiny but distinct, the Asian Citrus Psyllid heralds the impending demise of many local citrus trees.

By Les Harrison
Wakulla County Extension Director

Sometimes the news is just bad, and there is no way to sugar coat it.  The plant diagnostic lab at UF/IFAS North Florida Research and Education Center (NFREC) in Quincy has confirmed the presence of Citrus Huanglongbing (HLB) in the Florida panhandle, also known as citrus greening and yellow dragon disease.

Not surprisingly, the entomology program at NFREC also has confirmed Asian Citrus Psyllids in the region. This tiny insect is one of two psyllids which are known vectors or carriers of the bacteria which cause the citrus greening disease.

Not even ¼ of an inch in length, the Asian citrus psyllid, Diaphorina citri Kuwayama, is widely distributed in southern Asia. It is an important pest of citrus in several countries and is responsible for the destruction of production in several citrus industries regions in Asia and Africa

Until recently, the Asian citrus psyllid did not occur in North America or Hawaii, but it was first reported in Brazil in 1942. This pest was identified in Florida in 2005.

The adults have a mottled brown body with a light brown head. The forewing is broadest, mottled, and with a brown band extending around the edge of the outer half of the wing, but slightly interrupted near the top.

The antennae have black tips with two small, light brown spots on the middle segments. Under magnification a living Asian Citrus Psyllid is covered with whitish, waxy secretion, giving it a dusty appearance.

The adults leap when disturbed and might fly a short distance. They are usually found in large numbers on the lower sides of the leaves with heads almost touching the surface and the body elevated at a shallow angle.

Females may lay more than 800 eggs during their short lives. Eggs are laid on tips of growing shoots on and between unfurling leaves.

Juveniles pass through five development phases. The total life cycle requires from 15 to 47 days, depending upon the season and weather.

Adults have the potential to live for several months with nine to ten generation annually. Populations tend to be lower in winter.

The period of greatest activity of the psyllid corresponds with the periods of new growth of citrus. There are no galls or pits formed on the leaves to help identify this psyllid’s arrival. The developing nymphs are completely exposed.

Field recognition of greening disease can be difficult. Quite similar leaf symptoms can be caused by a wide variety of factors varying from nutritional disorders to the presence of other diseases such as root rot.

Symptoms of citrus trees infected display stunted growth, sparsely foliated branches, unseasonal blooms, leaf and fruit drop, and twig dieback. Young leaves are yellow to white, with green banding along the major veins.

Mature leaves have yellowish-green patches between veins, and midribs are yellow. In severe cases the leaves become chlorotic producing insufficient chlorophyll and have scattered spots of green.

Fruits on greened trees are small, generally lopsided, underdeveloped, unevenly colored, hard, and produce little juice. Most seeds in diseased fruits are small and dark colored.

Unfortunately, there are no citrus cultivars at this time, or practical treatments. The only good news is this is a reach priority and many scientists are pursuing a cure.

To learn more about identification and response to Asian Citrus Psyllids in Wakulla County, contact your UF/IFAS Wakulla Extension Office at 850-926-3931 or http://blogs.ifas.ufl.edu/wakullaco/

Photo Credits: Douglas L. Caldwell, University of Florida