Biology and Management of Anthracnose in

Strawberry

Gerald Holmes

Director

Colletotrichum: causal fungus of anthracnose diseases• Citrus

• Pepper

• Cucurbits

• Onion

• Spinach

• Blueberry

• Eggplant

• Tomato

• Potato

• Cabbage

• Beans

• Banana

Flower blight caused by C. acutatum

Dan Legard, CSC

Colletotrichum morphology

On runnerAfter incubation in moist chamberPhoto by K. Ivors

Wet spore masses need water splashing to spread

Or physical movement on people and equipment

Not windborne

History of anthracnose in Calif.

• Last major outbreak occurred in 2001-02

• Current outbreak in 2015-16• Mainly in Oxnard and Santa Maria

• Especially summer plantings in 2015

(Jan 1 – present)149 plant samples processed

25% Colletotrichum acutatum

10% Fusarium oxysporum9% Macrophomina phaseolina4% Verticillium dahliae4% Phytophthora spp.3% Cylindrocarpon destructans2% Colletotrichum gloeosporioides

43% Abiotic

2016 Summer planting: anthracnose only detected on non-dipped transplants (organic field)

2016 Disease Diagnostics

Management

• Begins with sanitation at nurseries

Foundation plants at low elevation nursery

High elevation nursery

Final plant increase prior to sale

Transplants for fruit production field

Management in fruit production

• Transplant dip

• Foliar fungicide application

Dip Treatmentsfor control of

Anthracnose Crown RotHaack, S., Adaskaveg, J., Forster, H. (UC Riverside)

Gubler, D., (UC Davis)

Ivors, K. and Holmes, G. (Cal Poly SLO)

Treatments

• Control (no water)

• Control (water rinse)

• Actinovate, 24 oz

• Azoxystrobin, 8 fl oz

• Bravo, 24 fl oz

• Switch, 8 oz

• Syngenta-1, 5 fl oz

• Syngenta-2, 7 fl oz

• EXP-13, 13.3 oz

• Exp-13, 26.6 oz

• Syngenta-1+EXP-13, 5 fl oz + 13.3 oz

= Zivion (ai = natamycin)

All treatments evaluated under these conditions:• Two types of pathogen

• Azoxystrobin-resistant isolates

• Azoxystrobin-sensitive isolates

• Two types of infection• Artificially inoculated

• Naturally inoculated

• Two cultivars• Portola (more susceptible)

• Fronteras (less susceptible?)

4-min dip w/ agitation

Drip drain for 5-10 min

Stored at 37F overnight

(Treated in afternoon; planted next morning)

Planted March 4, 2016at UCR Ag Operations

Anthracnose severity (0-4)(artificial inoculation – azoxystrobin sensitive)

Anthracnose severity (0-4)(artificial inoculation – azoxystrobin resistant)

Anthracnose severity(natural infection)

Petiole test yielded ~30% of crowns infected

Conclusions

• Artificial inoculation resulted in very high levels of disease and is an effective means of evaluating treatments

• Natural infection also resulted in high levels of disease• Treatments produced significant effects and yield

reductions

Conclusions

• Fronteras ~2X more resistant to anthracnose than Portola

• Actinovate: no efficacy measured under these conditions

• Azoxystrobin: highly effective IF Colletotrichum is sensitive• No efficacy IF Colletotrichum is resistant

• Switch: highly effective• No phytotoxicity detected under these conditions

• New compounds (EXP-13 and Syngenta-2) with high efficacy• Potential for registration of EXP-13 biofungicide (Zivion)

5-8 oz2-5 min

Hold plants <12 hours

Materials will be posted at:www.strawberry.calpoly.edu

Cal Poly Strawberry Center