Controlling Strawberry Powdery Mildew with …...Controlling Strawberry Powdery Mildew with Frequent...

Controlling Strawberry Powdery Mildew with Frequent Overhead Sprinkling with Water

Belachew Asalf, Andrew Dobson, David Gadoury, Arne Stensvand

Trends in strawberry production

2

• Plastic tunnels are popular

• Reduce gray mould, anthracnose, root rot

(Xaio 2001)

• But powdery mildew is major problem

Strawberry powdery mildew

• Podosphaera aphanis

• Obligate

• Heterothalic

• Short

generation

time

• High conidia

production

Symptoms and signs

4

Attack all parts of the plant except the root

Infection on the fruit

• Up to 50% yield reduction

• Fruit cracking and deformation

• Decrease fruit set

• Inadequate ripening

• Reduce shelf-life

Effect of water on powdery mildew

• Under open field production P.aphanis is not very important disease compared to tunnel

• The incidence of powdery mildew decreases as rain fall increases (Yarwood, 1957)

• Growers use overhead sprinkler to control powdery mildew in the nursaries

• Many laboratory experiments emphasize the detrimental effect of water on some powdery mildew species

• There was no quantitative information under field or tunnel condition

Hypothesis

• On the base of the literature and growersexperience, we hypothesized that P. aphanismight be directly suppressed by a water filmor the action of water applied throughoverhead sprinklers

Experimental design and plots

• High plastic

tunnel (9m X

29m)

• It had 6 rows

• Experiment

middle four rows

• Six

treatments

• Three reps

• RCBD

Treatments

1. Control

2. Water twice per week

3. overhead sprinkling for 1 minute with waterfour times per day (from 11:00 am - 3:30 pm)

4. Sulfur half the recommended rate twice perweek

5. Sulfur the recommended rate once per week

6. Signum (pyraclostrobin + boscalid) or Topas100 EC (penconazol) at recommended ratesalternately once per week

Incidence of Powdery mildew

Disease severity

0

10

20

30

40

50

60

10 17 24 30

Dis

ease

sev

erity

(%)

Days after inoculation

Unsparayed control Water twice per week

Water sprinkler 4 times per day Sulfur half dose twice

Sulfur full dose once Signum and Topas alternate

Powdery mildew Incidence on fruit at harvest

0

10

20

30

40

50

60

70

Control Water twiceper week

Watersprinkler

Sulfur halfdose twice

Sulfur fulldose once

Signum andTopas

alternate

Inci

denc

e on

frui

t (%

)

b

c

c

cc

a

Gray mould (Botrytis cinerea)

• Botrytis incidence was very low

0123456789

Control Watertwice per

week

Watersprinkler 4times per

day

Sulfur halfdose twice

Sulfur fulldose once

Signumand Topasalternate

Bot

rytis

inci

denc

e on

frui

t (%

)

a

ab

ab

bb

ab

How water affect powdery mildew?

• Mechanical washing of conidia

• Hydrophobic effect of the leaf and conidia (Lotus effect)

• Reduce conidia dispersal

• Conidial germination inhibition

http://www.ehow.com/info_12099041_drip-vs-overhead-watering-vegetables.html

Mechanical washing - water pressure

The Lotus Effect

Lotus leaf

• Lotus Effect is a striking feature of manyplant leaves that water tends to bead intodrops, and roll to the ground, collectingand washing particles and debris from theleaf surface. This self-cleaning mechanismis, termed the ‘lotus effect’.

• It may also play an important role inwashing away pathogen spores and conidia

Lotus effect

Lotus effect

Take off

Transportation

Landing

Conidia dispersal

Effect of water on conidial germination

Source:Peries, 1962

Summary• Frequent overhead sprinkler application of water reduced powdery mildew incidence and severity on both fruits and leaves.

The mechanism could be

• the lotus effect

• washing of conidia

• Reduced airborne conidial dispersal

• inhibit conidial germination

• It could be used to control powdery mildew in the nurseries and high tunnel.

• The timing is important to reduce the problem from gray mould.

Acknowledgement