Field Trial Artificial Infestation – Insect Pressure Assurance

Planning and executing a successful field trial is a large investment in time and resources requiring the effective coordination of multiple variables, many of which the trial coordinator has limited control over, such as weather or insect pressure of the targeted pest complex. Without sufficient plant damage, statistical differentiation of test treatments becomes difficult and has the potential to place the entire trail at risk. Crop protection candidates that have progressed through the stages of R&D, field trials, new product development, and commercialization, are often on the horizon.  With so much on the line, the inability to demonstrate efficacy in the limited window of a field season can lead to very costly commercialization delays.  

To remedy this frustrating and costly situation, Frontier Scientific Services assist the field entomologist and trial coordinators to address the insect pressure variable by adding control with high confidence outcomes.  This is achieved through a comprehensive Artificial Infestation Program tailored specifically for the field entomologist and trial coordinator’s requirements and guaranteed with our Insect Pressure Assurance.  We often begin working with the field coordinator during the preceding winter months during their planning period.  As their trial plans become defined with the number of trials, plot sizes, and projected planting dates, and artificial infestation requirements are developed including a draft of the shipment schedule defining the estimated shipment dates and egg quantities required for each trial location.

Once the tentative schedule is established we begin to make plans to size our cultures for the upcoming season, ensuring sufficient production quantities to supply all of our clients with overages built in to account for timing shifts and weather events.  As the actual ship dates come into focus we make final adjustments to the schedule coordinating closely with our client and execute shipments according to their release approval. With the uncertainty that summer weather can play, we include replacement options for rain out situations to ensure that your investment in insect pressure is established on the trial plots.

In summary here’s a general overview of Frontier’s Artificial Infestation Service:

1. Planning Period, March/Early April          
   1. Estimated egg quantities for each species and associated shipment dates for each field trial location provided by field coordinator; accordingly we schedule the colony ramp up dates, procure all necessary supplies, and check that we have all permits in place for each ship to location.
2. Technical Support
   1. Protocol recommendations
   2. USDA permitting requirements
3. Plant growth timing- planting & plant stage updates from field coordinator
   1. All shipment permits in place
   2. All materials on hand
   3. Colony ramp up
4. Final shipment dates confirmed by field coordinator
   1. Egg shipments executed to field cooperators
      1. Coordinated emergence and infestation times are synchronized
5. Insect Pressure Assurance Program
   1. Insects will be promptly replaced at no cost for re-infestation in the event of a weather-related events effecting their establishment on the test plants.

Example Protocol – Artificial infestation of Fall Armyworm (FAW) on Corn

1. Receipt of Eggs – FAW eggs are received on a wax paper substrate
   1. Eggs are shipped in an insulated container with packing supplements to control internal package temperature.
   1. Egg Inspection and transfer to neonate emergence containers
2. Egg Incubation
   1. Incubation setpoints and predicted neonate emergence time
      1. 28˚C       24-36 hours
      1. 21˚C       60-72 hours
      1. 12˚C       Egg storage up to 3 days; no development

Newly hatched larva of the fall armyworm, Spodoptera frugiperda (J.E. Smith).

Photograph by Lyle J. Buss, University of Florida.

• Larval Emergence and Formulation
  • Emerging larvae are mix into sterilized 20-40 mesh corn cob grit (Product #S3123) and transferred in an inoculation bottle (Product #F9146).
  • The inoculation bottle containing the eggs and corn grit carrier is capped with a Davis Insect Inoculator.
    • The bore size in the inoculation lever can be adjusted to the desired load volume
  • Mix the larvae/corn grit mixture by gently tumbling by hand
  • Moving the inoculator level back and forth dispense larvae/grit mixture onto white paper or similar and count the number of larvae observed per dispense.
    • Repeat this step a minimum of 3 times to confirm determine the average number of larvae per inoculator dispense
    • Concentrate to the target number of larvae by adding additional larvae to the mix
    • Dilute to the target number of larvae by adding additional grit to the mix
    • Cap the inoculation bottle containing the calibrated larvae and hold them at 60-70˚C as feasible.  The bottles may be placed in a cooler with cool packs to transit to the field.

• Artificial Infestation
  • Time of Day – as feasible try avoid dispensing the larvae at the hottest period of the day, mid morning once dew has evaporated or late afternoon are generally preferred when daily temperatures are over 90˚F.
  • Re-mix the larvae grit mixture by gently swirling the inoculator in a tumbling fashion and repeat occasionally during the infestation process.
  • Position the inoculator tube over the plant targeted plant tissue defined for the study; Generally FAW for corn will be directly over the inner whirl. 
  • Moving the inoculator lever back and forth dispense the larvae/grit mixture onto the plant.
    • To increase the number of larvae placed on a plant multiple dispenses can be performed, but it is important to be consistent with the infestation rate across all plants in the trial.
• Monitor the plants for establishment of the larvae on the infested plants
• Our recommendation is to wait at least 12 hours before applying any treatments so that the larvae can establish on the plants.

Author: Dave Davis

Sr. Director

Frontier Agricultural Sciences

                                                                                                                                                7/23/19