huanglongbing (hlb) symptoms in florida · •huanglongbing = yellow shoot • host range: all...

Huanglongbing(HLB)

Symptomsin Florida

Hilda D. GómezPlant Pathologist

HLBENVIRONMENTTIME

PATHOGENHOSTVECTOR

• A fastidious, phloem-limited Gram-negative bacterium• Irregularly distributed inside the host • Final identification using PCR• In Florida: Candidatus Liberibacter asiaticus causing Asian

form

PATHOGEN

ENVIRONMENT

• The Asian form occurs in warm climates and low altitudes (27-32 °C)

• Symptoms are more evident during the cooler months of the year

• Citrus cultivars grown in different areas could show different symptoms

• Symptoms: 2 months - 2 years (unclear)

• Symptoms observed in the present could be the expression of infections that occurred one or more years in the past

• This long and unclear latency period results in delayed disease diagnosis and pathogen detection

TIME

VECTOR Asian citrus psyllid

Lateral notching

Sooty mold

Burnt tip

RESULTING FROM THE PSYLLID FEEDING DAMAGE

• Huanglongbing = yellow shoot

• Host range: all citrus varieties and their hybrids, and some citrus relatives in the Rutaceae family

• None of the HLB symptoms are exclusive for the disease

• The most diagnostic symptom: blotchy mottle (common on all varieties)

• Other symptoms add to field detection

• Symptoms better observed in the interior part of the canopy

HOSTSYMPTOMS

Blotchy mottledistinctive symptom on leaves

Upper Lower

Citrus aurantium

ASYMMETRICAL

Citrusmacrophylla

Crosses lateral veins

Limited by the mid vein

Citrus limon

Blotchy mottle usually confused with

citrus leafminer feeding damage

Citrus x paradisi

Blotchy mottleprogression

EARLY

ADVANCED

Citrus aurantiifolia

Citrus maxima

Citrus reticulata

Citrus hystrix

X Citrofortunella microcarpa

Severinia buxifolia

Thicker leaf

Yellow veins Corky veins

“Rabbit ears”

“Green islands”

Multiple off season flowers

“Nutrient deficiencies”

HLB

Sectoring Dieback

Decay of root system, decline in vigorCitrus maxima

Severe leaf and fruit drop in a

commercial grove

Citrus sinensis

Symptoms on fruit

Citrus maxima

Vascular stain

Aborted seed

Citrus x paradisi

Rating of suspect samples (USDA)

High Classic HLB mottleZinc-like deficiency. Yellow veins. Corky veins. Misshapen or oddly colored fruits.

Medium Non-classic mottleYellow veins. Vein corking. Chlorotic leaves. Zinc deficiency.

Low Zinc and other general deficiencies. Mottling resulting from insect injury, fungal diseases, and mechanical damage. Naturally senescing leaves. Genetic variegation.

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