Search for Psyllid Economic Thresholds

Search for Psyllid Economic Thresholds
Cesar Monzo and Phil Stansly
Southwest Florida Research and Education Center
Institute of Food and Agriculture Sciencies
University of Florida
Introduction.
Current scenario:
SW Florida: Many blocks with 80% or more HLB infected trees.
Removal of infected trees not a viable option.
Positive results on the use of foliar nutrients applications for HLB
symptomatic trees.
Vector control together with foliar nutrient programs currently
seems to be the best strategy (Stansly et al.).
We still don’t know how low psyllid populations should be
driven to maximize profits from infected blocks.
Objective
To determine treatment thresholds for the
vector that optimize returns on investment in
citrus with a high incidence of HLB.
Introduction.
What an Economic Threshold?
"The density of a pest population below which the cost of applying control
measures exceeds the losses caused by the pest" (Glass 1975).
spray
Pest density (ACP per tap)
spray
Pest density critical value.
(Threshold)
Pest densities under the critical
value (threshold) don’t need to
be spray.
We can coexist with low pest
densities.
Time (days)
How much is this critical value?
Introduction.
Determining Economic Thresholds.
Economic Threshold:
Pest Management Costs = Potential Economic Damage
Pest densities < Economic Thresholds
Additional sprays will increase Pest
Management Costs more than the
benefits obtained from reduced
damage
Pest densities > Economic Thresholds
Additional sprays will reduce
damage more than the increased
Pest Management Costs.
Introduction
Pest Management Costs = Potential Economic Damage
Pest Management Costs
Potential Economic Damage
• Fruit Prices ~ Market situation
• Insecticide applications:
• Product Price
• Application costs
Juice quality
• Yield loss
Different ACP adult densities (different spray frequencies)
~
Yield Loss
Timing (Dormant Sprays)
Insecticides (Right decision)
Yield loss (%)
• Negative effect on beneficials:
ACP adult
density
= Pest Management Costs ????
• Incidence
on ACP
natural
Pest Density dependent
enemies (Qureshi et al. 2009)
• Incidence on secondary pests
100
0
Pest Density
Experiments.
Two 3-year studies:
Bob Paul (Block 1):
Tanner Road (Block 2):
Experimental design:
Randomized Complete
Block Design
(4 treatments x 4 reps)
Treatments:
No insecticide (1)
Calendar sprays (2)
0.2 ACP threshold (3)
30 acres
Early Gold (10 years old)
Estimated HLB infection: 98%
+ dormant spray
12 acres
0.7 ACP threshold (4)
+ dormant spray
Valencia (10 year old)
Estimated HLB infection: 80%
Blocks Management.
Calendar of applications:
2010
1. Spinetoram @ 4.5 oz (July)  
2. Dimethoate 4E @ 4 oz (Sept) 
Calendar applications 
No insecticide
0.7 ACP threshold 
0.2 ACP threshold 
2011
3. Danitol @ 8 oz (Jan)   
4. Diflubenzuron @ 6.24 oz (March) 
5. Carbaryl (April) 
6. Spinetoram (May) 
7. Imidacloprid (June) 
8. Abamectin (July)
9. Danitol (August)
10. Spirotetramat (September)
11. Carbaryl (October)
12. Phosmet (November)
13. Zeta-cypermethrin (December)
Nutrients program:
2011 (Feb)
Rate/ac
K-Phite
1 gal
13-0-44 fertilizer
12 lb
Techmangan (MnS04)
Zinc Sulfate
Sodium Molybdate
Epsom Salts
8.5 lb
2.8 lb
0.85 oz
8.5 lb
Sampling Methods.
ACP density
Tap sampling
HLB incidence
QPCR (Plants and ACP adults)
Harvest
Yields
Juice quality
Beneficials
Abundance :
• Tap sampling
• Suction sampling
Incidence on ACP
• Exclusion experiments
Secondary pests
CLM, Red Mites, Snow Scale
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Calendar applications
a
3
2.5
2
Adults/tap
3.5
Log Cumulative ACP Number
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
b
1.5
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
No insecticide
a
ab
1
0.2 ACP0.5
threshold
0
Calendar
No sprays
1.0
0.9
0.8
0.2 0.7
thrsld
0.6
0.5
0.4
0.3
= 6.03;
0.2 P
0.1
0.0
0.7 ACP threshold
threshold
0.7 thrsld
Adults/tap
Adults/tap
Adults/tap
ACP Adults by Treatment: Block 1 (‘Earlygold’).
Differences among treatments in
the Adult ACP cumulative numbers.
threshold
GLM (df = 3, 15: F
< 0.05)
Preliminary Results (First year Harvest).
25
20
15
10
5
0
-5 0
-10
-15
-20
500
Fruit quality:
1000
1500
2000
2500
Brix/acid or Lbs solids/box
Yield loss (%)
Yields:
12
Calendar appl.
10
No insecticide
0.2 ACP thrsld.
8
0.7 ACP thrld.
6
4
2
0
Adult ACP cumulative number
No trend for reduced yields with
increased psyllid counts after only one
harvest. Future results should allow us to
determine spray thresholds depending on
fruit prices.
Brix/acid
Lbs Solids
No significant differences in the
quality of the juice were found
among treatments of a same
block after the first harvest.
Beneficial arthropods.
Individuals per sample
Abundance:
60
No spray
50
1 spray
40
2 sprays
30
20
10
0
Parasitoids, predatory flies and spiders were the
most abundant beneficials. The spiders and the
arboreal ants appeared in lower numbers in the
treatment with two insecticidal sprays.
Beneficial arthropods.
Incidence on ACP:
60
No spray
50
1 spray
40
2 sprays
30
20
10
0
120
Eggs
100
ACP Numbers
Individuals per sample
Abundance:
Nymphs
80
60
40
20
0
Calendar
Caged
Parasitoids, predatory flies and spiders were the
most abundant beneficials. The spiders and the
arboreal ants appeared in lower numbers in the
treatment with two insecticidal sprays.
No spray Calendar
Caged
Uncaged
No spray
Uncaged
Pest reduction (%)
•
•
Calendar
69.1 ± 9.0
No spray
82.8 ± 4.9
ACP nymphs and eggs reduction due to
natural enemies can be more then 70%.
Reduction was 10% higher in the
treatment where no sprays are done.
Secondary pests.
1600
CLM:
CLM adults/trap
1400
1200
Trend toward lower CLM
populations in the
calendar spray treatment.
1000
800
600
400
200
0
0.2 Thrsld
0.7 Thrsld
Calendar
No spray
Secondary pests.
1600
CLM:
CLM adults/trap
1400
1200
Trend toward lower CLM
populations in the
calendar spray treatment.
1000
800
600
400
200
0
0.2 Thrsld
0.350
0.7 Thrsld
Calendar
No spray
Red Mites (Block 2):
a
Red Mites per Leaf
0.300
0.250
0.200
0.150
b
b
b
0.100
0.050
0.000
0.2 Thrsld 0.7 Thrsld
Calendar
No spray
Secondary pests.
CLM:
1600
CLM adults/trap
1400
1200
Trend toward lower CLM
populations in the
calendar spray treatment.
1000
800
600
400
200
0
0.2 Thrsld
Calendar
No spray
Red Mites (Block 2):
a
0.090
0.080
Red Mites per Leaf
0.300
0.250
0.200
0.150
b
b
b
0.100
0.050
Phytoseids per Leaf
0.350
0.7 Thrsld
0.070
0.060
0.050
a
a
ab
0.040
0.030
0.020
b
0.010
0.000
0.000
0.2 Thrsld 0.7 Thrsld
Calendar
No spray
0.2 Thrsld 0.7 Thrsld
Calendar
No spray
Calendar sprays treatment has significant higher numbers of red mites and
lower numbers of predatory mites (phytoseids).
Preliminary Conclusions.
Economic Thresholds for ACP control should provide criteria to optimize
profits in high HLB incidence trees by cutting out unneeded sprays during the
growing season.
No differences among treatments were expected or found in the first year, in
yields or juice quality.
In addition to product and application costs, insecticide sprays may exact a
price through negative effects on beneficial fauna. Some such effects are being
seen in the calendar spray treatment after one year.
Making the right decision about which insecticide to use can also help reduce the
probability of secondary pests resurgence caused by disruption of natural
enemies.
Acknowledgments.
Citrus Research and Development Foundation.
Bob Paul Citrus and Moreno Farms.
SWFREC Entomology Team.
Noel Rodriguez
Barry Kostyk
Benny Peña
Scott Croxton
Monica Triana
Miriam Ortez
Mauricio Pinto
Robert Riefer
Ted Stansly
Joel Mendez
Bryant Cawley
Zach Lahey
Dr. Katherine Hendricks
Shea Teams
Dr. Pamela Roberts
Dr. Jawwad Qureshi
Dr. José Castillo Dr. Moneen Jones
SWFREC Entomology Team
Kat Perez