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