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1
Southern Highbush Blueberry Disease overview for Florida
2017 Blueberry IST, Citra FL
Maria C. Philip F. Harmon, Ph.D.
Professor and Extension Specialist UF/IFAS Plant Pathology Department
Disease Happenings 2016Small Fruit
Blueberry42 Botryosphaeria Stem Blight Botryosphaeria sp./spp.30 No Pathogen Found23 Phytophthora Root Rot Phytophthora cinnamomi15 Anthracnose Colletotrichum sp./spp.10 Blueberry Leaf Rust Pucciniastrum vaccinii6 Bacterial Wilt Ralstonia solanacearum5 Algal Cane Blotch or leaf spot Cephaleuros sp./spp.4 Blueberry bacterial leaf scorch Xylella fastidiosa4 Powdery mildew Microsphaera vaccinii4 Target spot, Corynespora Corynespora sp.3 Girdling Roots Abiotic disorder3 Septoria leaf spot Septoria sp./spp.3 Phomopsis canker/stem blight Phomopsis sp.2 Phyllosticta Leaf Spot Phyllosticta sp./spp.2 Mushroom Root Rot Armillaria sp./spp.1 Botrytis, BRRV, Rhizoctonia, sootymold, crown gall, etc.
340Total for Blueberry
IPM Guide
• Seasonal guide
• Integrated options
• Based on the SE guide
Overview
Diseases present challenges at all stages of production
– Plant propagation considerations
– Pre‐bloom through petal fall
– Petal fall through harvest
– The rest of the year
• Late spring through summer
• Summer through winter/”dormancy”
Pre‐plant considerations
• Pre plant considerations– Cutting production, cultivar selection
• Clean plants, good cultivars
• Bacterial wilt, crown gall, stem blight, viruses
– Soil pH, drainage, bed construction• Root rot will be severe unless drainage is good
• Stem blight will be severe where root rot is present
• remove diseased, dead plants before replant
– Irrigation requirements• Source quality, pH, availability, app method
– Stem blight will be severe where insufficient or inconsistent
– Freeze protection
Bud break to harvest
• Petal fall through harvest
– Botrytis blossom blight
– Fungal fruit rots
• ripe rot anthracnose
• gray mold
• Alternaria
– Septoria leaf spot
– Leaf and fruit rust
– Phytophthora root rot
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Post harvest• Post Harvest
– Late spring through early summer• Anthracnose leaf and stem dieback• Septoria leaf spot• leaf rust• algal stem blotch
– Early summer through late fall• leaf diseases
– rust – anthracnose leaf spot– Phyllosticta leaf spot– target spot
• cane and root diseases– algal stem blotch– root rot– stem blight – bacterial wilt
Anything FL doesn’t have?
• mummy berry
• exobasidium
• viral scorch, stunt or shock
• nematodes
• What else?
Botrytis blossom blight
Management at risk because of multiple resistance
MFR2 2 fungicidesMFR3 3 “MFR4 4 “MFR5 5 “MFR6 6 “MFR7 7 “
Phenotype Resistant to
MFR = The same botrytisisolate may be resistant to 2,3, 4 or more fungicides,simultaneously.
From Amiri, Harmon, & Peres. Winter BGA meeting, Plant City, FL, 02/20/14
anthracnose fruit rotripe rot
“Anthracnose”
• There are 3 diseases referred to as anthracnose:
– Anthracnose fruit rot is also known as ripe rot (Colletotrichum gloeosporioides and C. acutatum)
– Gloeosporium leaf spot also known as anthracnose leaf spot and known to cause stem cankers as well (Gloeosporium minus)
– Anthracnose stem canker also known as dieback (Gloeosporium minus?)
• Not supposed to have structures called setae
• Dieback and cankers most prevalent on Flicker, also on Scintilla
3
“Anthracnose”
• Central Florida farms reported severe twig dieback, primarily on the Flicker variety in 2013
– Samples revealed Colletotrichum as the primary cause
– A review of spray records showed azoxystrobin use
– isolates were collected from a handful of farms and tested
• Growers reported increased incidence of ripe rot in 2014 in central Florida
– In 2015 and 2016 isolates from fruit, leaves and stems were collected and found to be resistant to QoI fungicides
Phyllosticta leaf spot
Gloeosporium leaf spot aka anthracnose leaf spot
anthracnose stem canker
anthracnose stem canker
Overlapping colony morphology from berry, stem, and leaf.
“Anthracnose”
Control
Azoxystrobin
Propiconazole
4
Diagnostic protocol
• Samples from UGA Extension were tested in 2016 using a diagnostic protocol at the same time as known resistant and sensitive FL isolates
• Approx. 20 isolates were tested and all from GA were sensitive
Managing anthracnose
• Do not use applications of only Abound, Cabrio, or Pristine on Flicker post harvest
• Rotate or tank mix DMI fungicides with compatible contact fungicides
• Do not apply more than the labels allow for any one active ingredient for the season
• Change between products with different active ingredients
Non‐fungicide options
• Overhead irrigation has been associated with greater disease severity—drip less so
• Sanitation
– use sanitizer on shears when pruning Flicker
– remove diseased plant material from the field and compost, bury, or burn it as appropriate
– plant varieties other than Flicker
Septoria leaf spotSeptoria leaf spot
Phyllosticta leaf spotPhyllosticta leaf spot
RustRust
5
Target spot, Corynespora
Blueberry necrotic ringblotch virus
Suspected mite vector
Bacterial leaf scorch—Xylella
Bacterial leaf scorch—Xylella
6
Bacterial leaf scorch—Xylella
Blueberry red ringspot virus
Blueberry red ringspot virus
Blueberry red ringspot virus
Crown Gall(Agrobacterium tumefaciens)
• Not a common problem as long as plants are free of disease from nursery
• Causes galls on roots and crowns
• Where the problem becomes established in a field, plant dips with product like Galltrol at the time of planting may help
8
Bacterial Wilt
• Caused by Ralstonia solanacearum
– Soil‐borne bacterium with a wide host range
– Common scourge of tropical agriculture
– Very difficult to control where it occurs
– Infects a wide host range of 250 species in 54 families
• First reported in Florida in 1897 on tomato
– Occurs commonly on tomato and potato (brown rot)
– Occasional problem of eggplant and tobacco in the last 100 years
Survival and introduction
• The bacterium is soil and waterborne
• Once introduced it can survive for years in infested waters including ponds and rivers and in wet soils deeper than 30 in
• It can survive in plant material without causing symptoms (latent infection)
• It can survive in weedy hosts (primarily solanaceous, like nightshade)
Infection
• Occurs primarily through roots– Wounds formed by lateral root emergence
– Wounds formed by root damage or feeding (root knot nematode and others)
• Infection of wounds in stems is also possible– Pruning wounds
– Insect feeding
• Infection and disease occurs at temperatures above 75F and below 95F
• Once in the plant, the bacterium spreads through the vasculature
Symptoms
• Similar to bacterial leaf scorch (Xylella)
• marginal scorching of leaves, dieback, stem blight, plant death
• symptoms move down the row more rapidly than across
• Xylem of plants loaded with bacterial ooze clogging vasculature causing wilt
10
Managing algal stem blotch
• Most fungicides do not work on algae
• Copper fungicides can help
– Two to four monthly applications in summer starting after harvest have been reported to keep the disease in check most years by growers
– Kocide 3000 (also Kocide 2000) as well as several other products and formulations of copper
– Avoid tank‐mixes of Cu products
• with phites and pesticides with EC formulation
Other methods?
• Phosphite fungicides applied for Phytophthoraroot rot management (but not immediately following copper) may help?
• Sprayers need to achieve good cane coverage
• Overhead irrigation will contribute to canopy wetness and disease
• Farthing, Primadonna, and older plantings of Emerald get the disease, Jewel is not affected
Any Questions?Philip Harmon, University of [email protected]