Citrus Canker and Citrus Greening Holly L. Chamberlain Smoak Groves AGRI-DEL, INC. Lake Placid, FL
Hurricanes 2004 and 2005 Challenges Facing FL Citrus Production Citrus Greening Competition Citrus Canker Development
Citrus Canker 1995 2006 eradication program 2006 present management / suppression / exclusion Regulatory Phytosanitary certification USDA-APHIS EuroGap protocols for fresh fruit shipment
Citrus Canker Bacteria (Xanthomonas axonopodis pv. citri) Spread by wind-driven rain, equipment, people, infected plant movement
2006 dry spring 2007 dry spring
Current citrus canker quarantine: August 2006 - Florida is currently under a statewide quarantine by the USDA and no citrus may leave the state unless the USDA has issued a limited permit. No Florida grown citrus may enter any citrus producing states or territories. Pre-harvest inspections must be completed for fresh citrus shipment to European Union, interstate movement, and Korea
Citrus Canker
u p p e r Young Leaf Lesions l o w e r
CANKER WATER-SOAKED MARGIN RAISED, CORKY LESION
YELLOW RING CANKER
Stem lesions of increasing age Older Stem Lesions Stem lesions progressing to dieback
Whenever you notice lots of premature fruit fall, a closer look for canker is warranted In this instance on grapefruit, enough defoliation has occurred to make fruit lesions the main feature of the disease
Fresh market: Profitability of grapefruit is of highest concern
Canker management practices post 1900ft. eradication program Decontamination Healthy nursery trees Susceptibility of cultivars Inoculum suppression / exclusion Windbreaks Copper sprays Leafminer control Cleaning for fresh frui
Decontamination
Nursery / Budwood Jan. 1, 2008 set point that existing trees will not be available due to current risk of exposure to diseases
Insect-proof nursery structures with windbreaks provide the greatest exclusion but will take time to site and build (2-3 years)
Host Susceptibility & Market Destination Highly susceptible grapefruit, some early oranges Susceptible Hamlins, tangelos More tolerant tangerines, Valencias Fresh (Fruit blemish) vs Processing (fruit drop)
Canker Control Products Only copper products are effective & feasible (COC and CuOH) In Brazil, Cu-based treatments reduced canker-induced fruit drop by 15-25%, even at reduced rates Antibiotics, SARs, disinfectants, and other materials have been extensively tested Many such materials have positive effects in lab and greenhouse tests, but none as effective as copper in the field
Windbreaks Most necessary for susceptible varieties Dependent on location Essential for fresh fruit production
Characteristics of Windbreaks Most necessary for susceptible varieties Dependent on location Essential for fresh fruit production Reduce wind speed to less than 20 mph (or 8 m/s) Avoid high density, no need to stop the wind, just slow it down Avoid very tall windbreaks, shade excessively, susceptible to breakage Windbreak distance effects 10X the height of windbreaks downwind, some upwind effect as well
Windbreaks (Grevillea robusta) are essential to reduce the effect of windblown rain on infection (10X the distance of the height of the tree)
Canker symptoms associated with leafminer wounds
Leafminer control Emphasis for YOUNG trees (up to 3 yr or 8 ft tall) Systemic insecticides for non-bearing trees Not needed for spring flush Spray oil and/or insecticides (Agri-Mek, Micromite, Spintor) on major summer flushes
Canker Management Inoculum exclusion & suppression Windbreaks Copper sprays Leafminer control No more hurricanes
CITRUS GREENING
Citrus Greening Leaf Symptoms Blotchy mottle pattern most typical with light green & dark green patches, no symmetry; prominent mid-vein
Citrus Greening Fruit Symptoms Curved columella, yellow stain at base of fruit button & aborted seeds
Survey, Sampling, Detection Survey great importance placed on locating all known infections in state Sampling for growers vs state More emphasis on visual diagnostics with practice less need for laboratory confirmation Laboratory for confirmation of new locations (counties, groves, etc)
Inspection Smoak groves: every row, every tree (4X/yr) Walk and ride Carts or platform
Sampling It matters what tissue you sample It matters what time of year
Time of Year
Symptomatic Field Trees
Testing to Date Lab started receiving samples last week of October 2006 Number of samples processed to date: 5500 Internal USSC 3700 Budwood registration 6300 Grove and nursery 15,500 Receiving up to 300/week
HLB Management Disease-free nursery stock SURVEY FOR EARLY DETECTION!! Removal of symptomatic trees Pruning is ineffective Reduce psyllid populations (biological or chemical)
Insect Excluding Nursery Production
Inspection / Detection
Infected Tree Removal
Citrus Greening Unknowns How long does it take the psyllid to acquire bacteria while feeding on symptomatic tissue? Can the psyllid acquire pathogen from asymptomatic tissue? How long before the psyllid can transmit pathogen? What are the thresholds for psyllid control? Additional diagnostics for field identification? Disease incidence in State of Florida? Is the pathogen seed-transmissable? Is the pathogen root graft transmissable? How long does it take for symptoms to manifest in different age trees? Symptomology? Blotchy mottle, green islands, yellow veining, vein corking, lopsided fruit, aborted seeds Age of infection? Production?