1. Incorporating Weather Information into the Insect Pest Management Decision-making Process
Larry Gut

2. Degree-days (base 50 F° post-biofix)
Current use
Predict egg hatch
Time insecticide sprays
Apr
May
Jun
adults
Early
Bloom PF
Delayed
egg
laying
hatch
Standard
100
250
500
1000
Degree-days (base 50 F° post-biofix)

3. Phenology models based on:
Impact of Temperature on Growth and development
Insects appear to be highly sensitive to temperature
Lower
threshold
Developmental rate increasing linearally
Rate of development
Upper
Lethal limit
Temperature

4. Use sine-wave function to calculate DD°
Degree-day: heat experienced by the insect when the temperature is one degree above the lower threshold for 24 h
Use sine-wave function to calculate DD°
Temperature
Horizontal cutoff
Upper threshold
Lower threshold
Time (24 hr period)

5. Accuracy of Codling Moth Degree-day Model
Year
Model
Calendar 79 80 81 82 83 84 85 86 87 93 -2 -1 2 3 4 13 2 8 18 1 -2 6
Moth
flight
Bloom
eggs
larvae
pupae
Apr
May
June
July
Aug
Sep
Calendar method: Spray 21 days after full bloom.
Model method: Spray 250 DD° after biofix.
Accuracy: Negative numbers indicate predicted timing was too late;
Positive numbers indicate predicted timing was too early.
Apple data, Brunner, Washington, USA

6. CM Degree-day table GDD Base 50 0 DD° = biofix 220-250 DD° 1000 DD°
Event
1st sustained moth captures
Start of egg hatch
Expected end of 1st
generation activity
Expected end of 2nd
Action
Set DD° = 0
First treatment if
over threshold
First 2nd generation
treatment if over
threshold

7. or can weather info assist us in other ways ?
Is that all there is,
or can weather info assist us in other ways ?
For example,
decide if treatment is needed
Decision models

8. Achieving control We know that weather can be an ally
mean CM / trap 14
Absence of 3-4 weeks of activity, 2004 12 10 8 6 4 2
May
Jun
Jul
Aug
Sep

9. We know something about how weather impacts activity
Flight from ca 3 h before sunset to 2 h after sunset
Active at temperature range of 55° F - 80° F
Moisture impedes activity

10. Large field-cage studies have provided some details
20m x 20m field cages enclosing 12 trees
Release know # of males and females
Mechanisms of mating disruption

11. Add a field flight tunnel, temperature sensors and evening research
Learn about weather impacts on CM activity

12. Cage experiments 100 males released in a cage
Discerning activity window
Temp. effect on activity
100 males released in a cage
pheromone traps checked every 15 minutes
Males held in small cage within the large field cage
observed every 10 minutes
flown in field wind tunnel every 10 minutes

13. Night of the experiment
Impact of temperature on male activity
Night of the experiment ºF
Flight temp.
Low activity periods
Grey boxes = periods during which wind tunnel observations were made.
Black numbers = % of observed moths that flew to a lure in a wind tunnel; grey numbers are the % of observed moths that engaged in pre-flight behavior (e.g., wing fanning).

14. Impact of delayed mating on fecundity
Viable offspring
per female
Knight, A IOBC
wprs Bull 20:
100
About 100 eggs/female
Laid singly on leaves and fruit, proportion dependent on host and cultivar
90% laid in first 5 days
Hatch in 6-14 days
Eggs are not being deposited if temp is below 62 °F 80 60 40 20
1-2
3-4
5-6
Female age when mated

15. Possible variables to model
Can we take advantage of the seemingly on-off effect of temperature on CM activity?
Possible variables to model
Degree hours during 4 hour flight period
Combined with low catch
Risk index