Suppression of Western Flower Thrips
by Overhead Sprinkler Irrigation
in Romaine Lettuce
John Palumbo, University of Arizona, YAC
Western Flower Thrips
in Romaine Lettuce
•
No reliable sampling plan
•
Lack of quantitative data on
damage description
•
Control is reliant on a few AI:
- Lannate + pyrethroid
- Success
•
Resistance is a concern
•
Lack of viable alternatives for
organic romaine production
Biopesticides
• azidirachtin
•
•
•
•
•
•
neem oil
pyrethrum
garlic extract
Hot pepper wax
Safer Soap
Sulfur
Overhead Sprinkler Irrigation
• Dislodge thrips from plants
• Repel adults
• Drown immatures on plant
• Suffocate pupae in soil
Objectives
• Determine the influence of sprinkler
duration, volume and frequency on
thrips populations.
• Evaluate the use of insecticide spray
regimes used in combination with
sprinklers for suppressing thrips.
Overhead Sprinkler Treatments
Duration/Volume
• 2 hrs (0.3 cm)
• 4 hrs (0.7 cm)
• 8 hrs (1.2 cm)
Frequency
• Weekly
- 9 hrs
• 2X weekly - 4.5 hrs
• 3X weekly - 3 hrs
Measurement of Thrips Abundance
Sprinkler Duration / Volume
40
40
Fall 2000
45 %
30
30
20
78 %
Mean WFT / Plant
10
20
10
0
None
2 hr
(0.3 cm )
4 hr
(0.7 cm )
150
40 %
120
8 hr
(1.2 cm )
Insecticide
treated
0
Spring 2001
90
120
90
75 %
60
30
0
150
60
30
None
2 hr
(0.3 cm )
4 hr
(0.7 cm )
8 hr
(1.2 cm )
Insecticide
treated
0
Romaine Harvest
Spring 2001
Trimmed Wt (g)
400
a
350
300
b
250
200
b
b
4 hrs
8 hrs
b
150
100
None
2 hrs
Sprayed
Overhead Sprinkler Treatments
Duration/Volume
• 2 hrs (0.3 cm)
• 4 hrs (0.7 cm)
• 8 hrs (1.2 cm)
Frequency
• Weekly @ 9 hrs
• 2X weekly @ 4.5 hrs
• 3X weekly @ 3 hrs
@ 1.4 - 1.8 cm / week
Sprinkler Irrigation Frequency
Spring 2002
Sprinkler Frequency
A
140
Total Thrips / Plant
120
Check
100
1X / week
80
60
3X
40
2X
20
Sprayed
0
28
Jan
4
Feb
11
Feb
18
Feb
25
Feb
4
Mar
11
Mar
18
Mar
Romaine Harvest
Spring 2002
Trimmed Wt (g)
a
500
450
b
400
350
c
bc
c
300
250
200
150
100
None
3X
2X
Spray Frequency
1X
Sprayed
Interaction of Sprinkler and Insecticides for
Thrips Suppression in Romaine
Alternated Sprays and Sprinkler Irrigation Runs at 5-6 d intervals
Fall 2001 Trial
Spray
Irrigation
Conventional
Sprinkler
Furrow
Lannate+Pyrethroid
Reduced-risk
Success
Organic
AzaDirect
Untreated
Sprinkler
Furrow
Rep I
Rep II
Sprinkler
Furrow
Sprinkler
Furrow
Rep III
Interaction of Sprinkler and Insecticides for
Thrips Suppression in Romaine
Fall 2001
Seasonal Avg. Thrips / Plant
25
20
Sprinkler
Furrow
15
*
10
*
5
0
Conventional
Reduced-risk
Organic
Untreated
Interaction of Sprinkler and Insecticides for
Thrips Suppression in Romaine
Fall 2001
Seasonal Avg .Trimmed Wt (g)
800
a
a
Sprinkler
Furrow
600
b
400
b
200
0
Conventional
Reduced-risk
Organic
Untreated
Interaction of Sprinkler and Insecticides for
Thrips Suppression in Romaine
Spring 2002 Trial
Spray
Conventional
Lannate ~ Succes rotation
Reduced-risk
Success ~ Assail rotation
Organic
AzaDirect+Garlic ~ Sulfur
Untreated
Irrigation
Sprinkler
Furrow
Sprinkler
Furrow
Sprinkler
Furrow
Sprinkler
Furrow
Arizona Crop Information Site
www.ag.arizona.edu/crops