Incorporating Weather Information into the Insect Pest Management Decision-making Process

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

2. Current use • Predict egg hatch • Time insecticide sprays Apr Jun May adults Early Bloom PF Delayed egg laying hatch Standard 500 0 100 250 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 Developmental rate increasing linearally Lower threshold Rate of development Upper Lethal limit Temperature

4. 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 0 0 -2 0 -1 0 -1 0 2 0 3 4 13 2 8 18 1 13 -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 Action Set DD° = 0 First treatment if over threshold First 2nd generation treatment if over threshold GDD Base 50 0 DD° = biofix 220-250 DD° 1000 DD° 1250-1300 DD° 2100 DD° Event 1st sustained moth captures Start of egg hatch Expected end of 1st generation activity Start of egg hatch Expected end of 2nd generation activity

7. 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 0 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 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. ºF Night of the experiment Impact of temperature on male activity 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. 1997. IOBC wprs Bull 20: 203-206 100 • 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 0 1-2 3-4 5-6 Female age when mated

15. 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