Anthracnose and Algal Stem Blotch on Southern Highbush Blueberry in Florida

FBGA Fall 2014 Blueberry Short Course

Philip F. Harmon, Ph.D.

Associate Professor and Extension Specialist

UF/IFAS Plant Pathology Department

Disease happenings 2014 Blueberry Samples so far 2014

28 Phytophthora crown and root rot Phytophthora sp./spp.

22 Anthracnose Colletotrichum sp./spp.

21 BRRV Blueberry Red Ringspot Virus (BRRV)

18 Botryosphaeria Stem Blight Botryosphaeria sp./spp.

15 Bacterial Leaf Scorch Xylella fastidiosa

4 Gray Mold Botrytis cinerea

3 Pestalotia leaf spot Pestalotia sp.

2 Blueberry Leaf Rust Pucciniastrum vaccinii

2 Phomopsis Leaf Spot /Twig Blight Phomopsis sp./spp.

1 Crown Gall Agrobacterium tumefaciens

1 Phyllosticta Leaf Spot Phyllosticta sp./spp.

53 Bacterial Leaf Scorch Not Detected Xylella fastidiosa

21 No Pathogen Found (in tissue submitted)

5 Insufficient Sample-PFD Problem further down

3 BRRV Not Detected Blueberry Red Ringspot Virus (BRRV)

3 Insect Damage Insects

2 Phytophthora Not Detected Phytophthora sp./spp.

2 Insufficient Sample

2 Nutrient Imbalance Suspected

208 Total for Blueberry

“Anthracnose”

• There are 3 diseases referred to as anthracnose:

– Anthracnose fruit rot is also known as ripe rot (Colletotrichum gloeosporioides)

– 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 also (Gloeosporium minus?) • Not supposed to have structures called setae

• Dieback and cankers most prevalent on Flicker, also on Scintilla

anthracnose fruit rot ripe rot

Phyllosticta leaf spot

Gloeosporium leaf spot aka anthracnose leaf spot

anthracnose stem canker

Control Azoxystrobin Propiconazole

Resistance to QoI fungicides

• The stem canker pathogen is resistant to:

– QoI fungicides (azoxystrobin, pyraclostrobin)

– Abound, Cabrio, Pristine

• Four farms were sampled, all isolates were resistant, send samples to confirm resistance on your farm to the UF Plant Disease Clinic

Managing anthracnose

• Do not use applications of only Abound, Cabrio, and 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

Fungicides to look into

• DMI fungicides include products:

– Tilt and Orbit, Indar, Quash, a new product Proline

• Contact fungicides include:

– Bravo, Captan, Kocide, Omega, and Ziram

• From what I’ve seen, Flicker will require frequent rotations of these fungicides when rains are regular and disease is likely

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

algal stem blotch

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 Phytophthora root 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