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

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)

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

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)

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

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

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

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

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

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

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

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

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).

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 1-2 3-4 5-6 Female age when mated

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