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Arne Stensvand, NIBIO/NMBU

Physical means to control

powdery mildew

Overhead water misting

Ultraviolet (UV) light

Warm water steam

(‘Plant Sauna’)

Photo: E. Fløistad

Collaborators • NIBIO/NMBU: A. Suthaparan, K. Solhaug, H.

Gislerød, R. Pathak, N. Johansen, N.

Trandem, B. Asalf, A. Stensvand

• Cornell Univ: D. Gadoury, T. McCann

• Univ of Florida: N. Peres, R. Onofre

• USDA: L. Cadle-Davidson, B. Turechek

• RPI Lighting Research Center: M. Rea, A.

Bierman, J. Patel, M. Figueiro, L. Radetsky

• Myhrene AS: O. Myhrene, S. Myhrene

• Saga Robotics AS: P. From, E. Altenborg

• Ushio America: K. Cordero, C. Holger

• OSRAM Americas: L. Brock

Financing • Research Council of Norway

• Norwegian Agriculture Agency

• H2020 – EU (GoodBerry)

• USDA OREI/SCRI

Photo: E. Fløistad

Overhead water sprinkling

Very efficient against powdery mildew

Reduces spider mites with 30-60%

No negative effects on predatory mites

Photo: A. Stensvand

• Spores attach to the surface of water

droplets, roll off the leaves

• Fungal hyphae carrying the spores will break

• Water prevents spore germination Photo: B. Asalf

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Experiments in Florida and Norway

Overhead misting/sprinkling

1 minute 4 times per day

Photo: R. Onofre

Results from high tunnel experiments in Norway

Similar results in Florida in open field and high tunnel

Avoid overhead misting in moist, damp weather that may stimulate

grey mould and other pathogens thriving in wet conditions

Photo: A. Stensvand

UV No UV

Treatments during night

Photo: R. Onofre Photo: A. Stensvand

UV < 300 nm reduces powdery mildew

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Several research groups, including

at Hoogstraten in Belgium and

USDA in West-Virginia

UV against grey mould

Dutch company offering

UV equipment to control

fungal pathogens

Research on UV in several countries

As good or better

than the best

standard fungicide

Tractor-mounted UV unit in Florida

Photo: A. Stensvand

Tried out by a commercial

strawberry producer

(Myhrene) in 2016-2018

Photo: A. Stensvand

«Thorvald» (Saga Robotics) «Thorvald» at a field day with Myhrene 5 June 2019

Ellen Altenborg,

Saga Robotics

Treated 1.1 hectare 2-3 times per

week in cv. Murano in 2019 – no

development of powdery mildew

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Charging container

for the UV unit

‘Murano’

‘Sonata’

Five applications with Topas, Amistar

and Signum in cv. Sonata; gave up the

production one month ahead of time

due to powdery mildew Foto: E. Altenborg

UV effect against two-spotted

spider mites: Kills 99-100% of eggs, larvae

and nymphs if exposed directly, but minor effect on adults

Photo: K. Westrum

UV effect against grey

mould: Can strongly reduce

the disease at high doses, but

that may not be applicable in an IPM system

Testing at Lassen Canyon

Nursery in California

Test units built in California,

Florida and Norway by Ole Myhrene

Goal: Reduce/eliminate diseases

and fungicide resistant strains from

transplants of strawberry

Recipe from Florida:

1 hour pre-treatment at 37°C

1 hour at 20-25°C

4 hours at 44°C

Very good effect against angular

leaf spot, anthracnose, grey mould,

crown rot, powdery mildew Photo: W. Turechek

The ‘Plant Sauna’

Powdery meldew killed

after 2 or 4 h at 40-44°C

Living, sporulating powdery

mildew on untreated plants

‘Plant Sauna’ treatments of strawberry transplants

Photo: B. Asalf

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Experiments with bare root

plants in Florida No

negative effect on yield

Experiments with mites in

Norway No effects on

spider mites, but all stages

of strawberry mites killed

Photo: A. Stensvand

Upscaling of the ‘Plant Sauna in NL

by the Myhrene and Barel companies

Photo: Ruud Venner

Conclusions

Overhead water misting and UV controls powdery

mildew as efficiently as fungicides – must be adapted

to IPM-strategies with beneficials

The Plant Sauna eliminates powdery mildew in

transplants – possible growth and yield reductions must

be tested with various cultivars and plant qualities Thanks! «Thorvald» in a commercial

strawberry field in Florida