potato data slides 1994

1
Potato Disease Management
One Step Forward . . . and Two Steps
Back
W. R. Stevenson UW Madison, Plant Pathology
2
Potato Late Blight
3
Potato Late Blight
4
Potato Late Blight
5
Potato Early Blight
6
Potato Early Blight
7
Pink Rot
8
Silver Scurf
9
Rhizoctonia
10
The 2000 Growing Season At A Glance

• Early start to the planting season
• Excess rainfall in late May and early June
• Abundant rainfall during July, August, early
  September
• Warm, but not hot temperatures throughout summer
• Relatively even growing season without temp or
  heat stress
• Excessively warm temperatures during harvest and
  early storage along with period of nighttime
  frosts

11
The 2000 Growing Season At A Glance

• The outcome during the growing season
• Accumulation of 18 severity values by June 1
• Appearance of first late blight in first half of
  June
• Subsequent scattered late blight
• statewide, but no widespread epidemic
• Intense fungicide spraying - statewide
• Minimal early blight
• The appearance of a smooth, high quality crop
• Large tubers with high dry matter

12
The 2000 Growing Season At A Glance

• The Outcome
• At Harvest and Early Storage
• Swollen lenticels at harvest
• Pink rot observed at harvest
• Some late blight on tubers
• Unusually high levels of bruising
• Warm tubers at harvest
• Field frost
• Inability to cool tubers in early storage
• Unwanted moisture in early storage
• Reduced air circulation with cool nighttime air

13
The 2000 Growing Season At A Glance

• The Outcome
• Film of water on tubers at harvest
• Inability to control bin temperatures
• Symptoms of leak, bacterial soft rot, pink rot,
  late blight
• Appearance of mold on tubers generally
  saprophytic molds
• Loss of stored potatoes to combination of problems

14
Potato Disease Management

• Storing warm tubers gt 65 F increases risk of
  decay
• Action Discontinue harvest when pulp temp gt 65
  F
• Film of water on tubers at harvest or sweating in
  storage increases risk of decay
• Action maintain air circulation to remove
  excess moisture
• Tuber respiration increases up to 25 fold in the
  first 24 hr after harvest
• Consequence CO2 ? O2 ?
• Action maintain air circulation at these
  critical times

15
Potato Disease Management

• Shutting off fans when outside air temp gt pile
  temp
• Failure to remove surface moisture
• Decrease in available O2
• Increase in pulp temperature
• Increase in risk of soft rot decay
• Potential for tuber black heart
• Increased risk of storage losses

16
Potato Disease Management

• The question of Quadris use
• Testing in WI since 1996
• EUP in 1998 16 growers with split fields
• Full label in 1999
• Allegations in 2000 regarding
• Plant height
• Tuber skinning
• Tuber bruising

• Tuber decay at harvest
• Tuber decay in storage
• Fry color

17
Potato Disease Management

• Quadris evaluation trials
• Paired comparisons
• multiple varieties
• with and without Quadris application
• No observed differences in
• Plant height or vigor
• Tuber skinning or bruising at harvest
• Tuber decay at harvest
• Tuber decay in storage
• Fry color

18
Benefits of Quadris Treatment

• Since 1996 multiple trials Hancock, Spooner,
  grower trials
• Standard program Three sprays beginning at row
  close and alternated with protectant (mancozeb or
  chlorothalonil)

19
Benefits of Quadris Treatment

• Observations
• Consistent and excellent control of early blight
  and late blight
• Control of Rhizoctonia stem canker and black
  scurf
• Reduced incidence of black dot
• Improved crop health, yield, tuber size
• Improved yield, larger tubers
• Reduced amounts of a. i.
• Cost effective

20
Potato Disease Management

• Question
• If we are achieving a high level of blight
  control at Hancock with high disease pressure,
  why are many growers having poor control with
  much higher inputs ?????

21
Benefits of Quadris TreatmentHancock Potato
Trial, 2000
AUDPC - Combined
Foliar Disease Severity - Combined
LSD (P0.05) 0.05
22
Benefits of Quadris TreatmentHancock Potato
Trial, 2000
cwt/A
US 1
23
Potato Fungicide Trial - Hancock, WI - 2000Early
and Late Blight Control Selected Treatments
Foliar Disease Severity - Combined
AUDPC - Combined
Standards
24
Potato Fungicide Trial - Hancock, WI - 2000
AUDPC and Yield
Yield (cwt)/A
AUDPC - Combined
Standards
25
Potato Fungicide Trial - Hancock, WI -
2000Efficacy, Active Ingredient and Toxicity
Units
a. i. (lb/A)
Toxicity Units
AUDPC
Standards
26
Potato Fungicide Trial - Hancock, WI - 2000Early
Blight Control Promising Experimentals Efficacy
AUDPC
Foliar Disease Severity Early Blight
Combined
Standards
Early Blight
27
Potato Fungicide Trial - Hancock, WI 2000
Promising Experimentals Early Blight Control
AUDPC and Yield
Yield (cwt)/A
AUDPC
Combined
Standards
Early Blight
28
Potato Fungicide Trial - Hancock, WI - 2000Late
Blight Control Promising Experimentals Efficacy
AUDPC
Foliar Disease Severity Late Blight
Late Blight
Standards
Combined
29
Potato Fungicide Trial - Hancock, WI 2000
Promising Experimentals Late Blight Control
AUDPC and Yield
Yield (cwt)/A
AUDPC
Combined
Standards
Late Blight
30
Potato Disease Management

• New Products in the Pipeline
• Gavel registration likely for 2nd quarter 2001
• Headline (BAS 500) possible registration in
  2002
• Tanos possible registration in 2003

31
Potato Fungicide Trial - Hancock, WI - 2000Early
and Late Blight Control Nozzle Types
32
Potato Fungicide Trial - Hancock, WI - 2000Early
and Late Blight Control Nozzle Types

• Excellent wear life - ideal for abrasive spray
  materials.
• Produce smaller droplets for thorough coverage.
• Spray pressure - 40-300 PSI

33
Potato Fungicide Trial - Hancock, WI - 2000Early
and Late Blight Control Nozzle Types

• Excellent spray distribution over a wide range of
  pressures - 15-60 psi
• Reduces drift at lower pressures, better coverage
  at higher pressures

34
Potato Fungicide Trial - Hancock, WI - 2000Early
and Late Blight Control Nozzle Types

• Mixes air with the liquid being sprayed to
  produce large air-filled droplets
• Large spray droplets reduce drift
• Improved crop penetration
• Excellent target cover and retention
• Venturi technology all contained in the nozzle
  tip makes it very economical.

Air drawn in through side port
Spray liquid enters nozzle
Air liquid mix
Large droplet size
Droplets contain air bubble, shatter on impact
with target
35
Potato Fungicide Trial - Hancock, WI - 2000Early
and Late Blight Control Nozzle Types

• Penetrates crop residue or dense foliage
• Smaller droplets for thorough spray converge
• Nozzle spacing 20 inches
• Spraying pressure 30 to 60 PSI

36
Potato Fungicide Trial - Hancock, WI - 2000Early
and Late Blight Control Nozzle Types

• Uniform coverage in broadcast spraying
• Larger droplets for less drift - large,
  air-filled drops through the use of a venturi
  air-aspirator
• Excellent wear characteristics

37
Potato Fungicide Trial - Hancock, WI - 2000Early
and Late Blight Control Nozzle Types
Foliar Disease Severity - Combined
AUDPC - Combined
38
Potato Fungicide Trial - Hancock, WI - 2000
AUDPC and Yield Nozzle Types
Yield (cwt)/A
AUDPC - Combined
Standards
39
Potato Fungicide Trial - Hancock, WI -
2000Active Ingredient and Toxicity Units
Nozzle Types
Active Ingredient (lb/A)
Toxicity Units
Standards
40
Promising VarietiesHancock Potato Trial, 2000
AUDPC - Combined
Yield (cwt/A)
Foliar Disease Severity - Combined
41
and comments . . .