1

Three Common Lethal Soil-borne

Pathogens in California Strawberry

Disease Pathogen Host plant Survival in soil

without a host

Verticillium

wilt (1932)*

Verticillium

dahliae

>300 species

incl. >100 weed

species

8-10 years

Fusarium wilt

(2009)

Fusarium

oxysporum f.

sp. fragariae

Strawberry only < 3 years

Charcoal rot

(2008)

Macrophomina

phaseolina

Strawberry only

(?)

< 3 years

* Year first reported in CA

Crop Rotation for Strawberry

• Traditional method to avoid soil-borne

diseases in strawberries worldwide

- Significant parts of strawberries in the world

are produced by rotation-based IPM approach

without using fumigants

- Minimum of a 3-year break between two

strawberry plantings recommended in EU and

Northeast US and Canada

- Mandatory for organic strawberry production

under the National Organic Program

Verticillium dahliae;Host Crops vs. Non-host Crops

• Host crops

caneberry (raspberry, blackberry), blueberry,

artichoke, cucumber, watermelon, pumpkin,

eggplant, lettuce, pepper, mint, potato, spinach,

tomato

• Non-host crops

cauliflower, cabbage, celery, parsley, radicchio,

onion, garlic, bean, pea, carrot, sweet potato,

asparagus

• Suppressive crop

broccoli

Suppression of spinach Fusarium wilt by intercropping with Allium plants (Igarashi et al., 2017)

Allium roots -> gamma-Glutamyl-S-allylcysteine -> Flavobacterium --> Fusarium wilt suppression

Good Rotation or Bad Rotation?

Host Non-Host Suppressive

Year 1 Year 2 Year 3 Year 4 Year 5

Strawberry Potato Strawberry Pepper Strawberry

Strawberry Sweet

potato

Tomato Spinach

Lettuce

Strawberry

Strawberry Spinach

Broccoli

Cauliflower

Cabbage

Cabbage

Broccoli

Strawberry

Strawberry Lettuce

Broccoli

Lettuce

Broccoli

Wheat (Summit 515)

Onion

Strawberry

Strawberry Broccoli

Lettuce

Broccoli

Lettuce

Broccoli

Lettuce

Strawberry

Specific wheat varieties can suppress charcoal rot in strawberries: Plant survival rate (cv. Monterey) (Ivors, 2015)

• Strawberry disease diagnostic: Dr. Shashika S. Hewavitharana, Cal Poly SLO. Email: shewavit@calpoly.edu Phone: 805-756-2856

• Disease resistance of UC varieties: https://www.calstrawberry.com/en-us/Pest-Management/Breeding

Diseases

Soil-borne disease management in organic strawberries; Crop rotation and ASD Joji Muramoto, Assistant CE Organic Production Specialist, UCSC. joji@ucsc.edu

2

Anaerobic Soil Disinfestation (ASD)

With ASD we

consistently get an

80-100% reduction

of Verticillium dahl-

iae microsclerotia in

soil using 9 ton/ac of

rice bran as a carbon

source.

Yields under ASD

generally equivalent

to fumigant controls.

For suppressing

Fusarium wilt and

charcoal root rot,

higher soil tempera-

ture is required.

In the 2018-19 sea-

son, >1,700 acres of

berry fields in CA

were treated by

ASD.

For more information please contact:

Dr. Carol Shennan cshennan@ucsc.edu

831 345 7594

Dr. Joji Muramoto joji@ucsc.edu

831 247 3804

1. Spread carbon source such as rice bran at 6-9 t/ac

2. Incorporate in soil

3. Form beds and lay drip tape

4. Cover with plastic tarp

5. Drip irrigate < 1.5 ac-in and keep above field capacity

6. Leave for 3 weeks

7. Punch holes in plastic

8. Transplant straw-berries a few days later

Special points of interest: • Briefly h ig h lig h t you r p oin t of in terest h ere.

• Briefly h ig h lig h t you r p oin t of in terest h ere.

• Briefly h ig h lig h t you r p oin t of in terest h ere.

• Briefly h ig h lig h t you r p oin t of in terest h ere.

ASD was developed as an

alternative to soil

fumigation in the

Netherlands and Japan,

and is currently used in

these and some other

countries.

It integrates the principles

of solarization and

flooding for places where

these practices are not

feasible or effective.

It has been found to be

effective at suppressing

many soil-borne diseases,

as well as nematodes for a

range of crops.

Where temperatures are

high enough, it may also

control weeds.

History of ASD

How to do ASD

ASD Rice bran 9 t/ac

Grower’s standard

April 23, 2015

Oxnard Demonstration Trial (organic site. Pico sandy loam)

3

1. Mowing cover crops 2. Adding rice bran 3. Chiseling and rototilling

4. Applying clear TIF

and drip tapes

5. Drip irrigation

(1.5 ac-inches)6. Summer flat ASD w/ clear TIF

(July 19 –August 28, 2017)

Cover Crop-Based Summer Flat ASD Treatment (July-Aug 2017)

Pathogen

Temperature

C source

Type & Rate

Organic acids

Microbial shifts

Anaerobiosis

Water Depth and time

Crop

genotype

Soil type

/management

history?

ASD Management Triangle (Shennan et al, 2014)

ASD Fall

RB 9t/acUTC

Fusarium oxysporum f. sp. fragariae infested fieldStrawberry plants (8/14/14)

* First reported in CA strawberries by Koike et al., 2009

ASD Summer

RB 9t/ac

Higher temperature threshold for Fusarium oxysporum(>460 hours above 86°F at 8” soil depth (Muramoto et al., Acta Hort. In Press))

Cumulative mV hrs with Eh below 200mV – threshold for V. dahliae control at ~50,000 (25 oC)

0

10

20

30

40

50

60

70

80

0 50,000 100,000 150,000 200,000

V. d

ah

lia

e m

icro

scle

roti

a #

/g s

oil

Cumulative Eh mV

15 deg C

25 deg C

hrsBelow 200mV

V. dahliae

threshold

(=59 deg F)

(=77 deg F)

(Shennan et al., 2010)

Both anaerobic condition and temperature are important for disease control in ASD

Fermentation ~key process in ASD~

• An anaerobic (lack of oxygen) • bacteria, yeast or other

microorganisms convert organic foods into simpler compounds

ASD process • acetic acid• butyric acid• propionic acid• lactic acid• some other volatiles • using native microorganisms in

soil

4

Key Practices for Successful ASD

• Broadcast rice bran when the soil moisture is ready for bed listing• Avoid aerobic decomposition of C-source

• Mix C-source with soil uniformly• Rotor tiller would be the best

• Apply mulch immediately followed by bed listing• Preserve soil moisture and reduce the amount of drip irrigation

• Goal: <1.5 acre-inches during 3 week period

• Monitor soil Eh or odor during ASD

• Use with appropriate crop rotation• Broccoli for Verticillium, wheat Summit 515 for Macrophomina, allium

crops for Fusarium

• Can use summer cover crop as a partial carbon source• Replace a part of rice bran to reduce the cost

PPF effect

Pre-plant fertilizer (PPF) can be eliminated

under ASD with rice bran (RB) 9 tons/acRhizoctonia infested field, Watsonville, CA (Zavatta et al., 2014)

* 6 tons/ac

bed top

application =

~9 tons/acre

broadcast

application

PPF: 650

lb/ac of

slow-

release

18-6-12

Disease suppression effect

GP: grape pomace

N MINERALIZATION FROM RICE BRAN (N: 2%, P2O5: 3%, K2O: 1%, CN: 20)

Aerobic (RBF): 25-30%

Anaerobic (ASD) then aerobic: 20-25%

ASD (Anaerobic soil disinfestation)

RBF (Rice bran farming)

9 tons/ac-> total N 360 lb-N/ac

-> plant-available N: ~75-100 lb-N/ac in 6 months

…Need in-season N!

Long-term effect of ASD on V. dahliae

0

2

4

6

8

10

UTC M

C

ASD

ASD

+MC

UTC M

C

ASD

ASD

+MC

UTC M

C

ASD

ASD

+MC

Fallow CauliflowerCauliflowerCauliflowerCauliflowerBroccoliBroccoliBroccoliBroccoli

V. d

ah

lia

e m

icro

scle

roti

a #/

g so

il

V. dahliae microsclerotia number in top soil

(Org. site. Post lettuce. Sep. 2013. 2 years after ASD treatment)

Fallow Cauliflower Broccoli

Main (P=0.37): n.s.Sub (P=0.02*): ASD ASD+MC MC UTC

Main x Sub (P=0.32): n.s.

Fallow

Cauliflower ASD and/or MC/strawberry/winter cover crop/Romaine lettuce

Broccoli(Shennan et al., 2016)

UTC: untreated check

MC: mustard cake

ASD: anaerobic soil disinfestation

Measure of genetic similarity of fungal communities after ASD treatment in CA

ASD including RB

Fumigants

Untreated and Molasses ASD

(Shennan et al., 2018, Plant Pathology)

MSM*2 ASD

MSM2+RB**3

ASD

RB9

Grower

Standard

May 29, 2014Oxnard Demo Trial (Macrophomina phaseolina infested organic field)

Macrophomina phaseolina control by ASD

(Muramoto et al., 2017. Int. J. Fruit Sci.)

*MSM: mustard seed meal, **RB: rice bran