INTERNAL FRUIT APPEARANCE

• Symptomatic fruit may have aborted, dark-colored seeds, and the central core may be curved. The juice vesicle color may lighten, moving from the peel to the middle of the fruit.

• Additionally, in past years crystals (believed to be hesperidin) have been observed on the segment membranes, and the albedo may take on a bluish tinge (such observation is not common at present)

EXTERNAL FRUIT APPEARANCE

• Symptomatic fruit appear lopsided (A), often oblong (B), with a tendency to be smaller than normal (C), and frequently with an inverted color change (green shoulders, orange blossom end). Additionally, fruit often have a yellow stain below the calyx (point of stem attachment, D) when compared to healthy fruit (E).

FRUIT SIZE AND YIELD

• HLB-affected trees have a significantly greater portion of fruit in smaller size categories compared to healthy trees—over 95% of symptomatic fruit are < 2.25" in diameter.

• Most HLB-symptomatic fruit could be eliminated by removing fruit that is < 2.25" in diameter.

• Total juice volume produced will be less from HLB-positive trees due to smaller fruit size.

• HLB-affected trees appear to have good yields at least one year after known infection.

• Yield does not appear to be consistently reduced until > 25% of tree canopy is symptomatic.

• Treatments to improve tree health may not improve fruit size, but appear to slow within tree disease spread and maintain total yield.

FRUIT QUALITY

• The ratio of sugars to acid (Brix/acid ratio) is used as a maturity and quality indicator. Three types of fruit were compared:

• Control fruit that was harvested from a non-infected tree

• Asymptomatic fruit that did not show physical symptoms of HLB, but came from an HLB-affected tree

• Symptomatic fruit that did show physical symptoms of HLB and came from an HLB-affected tree

• Brix/acid ratios were as much as 13%–24% lower and acid levels were as much as 18% higher in symptomatic juices compared to control.

• Juice from symptomatic fruit was less sweet and more tart/sour than that from control fruit. Symptomatic juice appears to be from less mature fruit, even though the juices are from fruit of the same age.

• Potential immature flavors in HLB fruit make removal desirable.

• Only symptomatic fruit from HLB-affected trees show quality changes (rendering it similar to immature fruit).

HUANGLONGBING HISTORY

• Huanglongbing is a plant disease caused by Candidatus Liberibacter asiaticus, a phloem-limited bacterium affecting all citrus cultivars.

• In 1995, the official name for citrus greening became Huanglongbing (HLB).

• The vector, Asian citrus psyllid, was first found in Florida in 1998.

• HLB was first detected in south Florida in August 2005.

• As of October 2006, HLB-affected trees had been found in twelve counties.

• Thirty-two counties had confirmed HLB in their area by the end of 2008.

• By February 2010, thirty-four counties (dark blue on map), including all commercial citrus producing counties, were confirmed positive with at least one HLB-affected tree.

• Symptoms can be found year-round, but are more prominent September through March.

CONTACTS

Tripti Vashisth

Horticultural Sciences

863-956-8846

Yu Wang

Food Science and Human Nutrition

863-956-8673

Michelle Danyluk

Food Science and Human Nutrition

863-956-8654

Renée M. Goodrich-Schneider

Food Science and Human Nutrition

352-392-1991 ext. 208

Charlie Sims

Food Science and Human Nutrition

352-392-1991 ext. 211