1. Challenges and Considerations of Field Sampling for Pesticide Residue Analyses
Tim Creger, NDA Pesticide Program Manager
Eric Fuentes-Ruiz, NDA Pesticide Inspector II

2. Topics Covered: Reasons for collecting samples
Types of samples typically collected
Sampling Decision-Making (the ‘why’ behind the type of sample collected)
Sampling Protocols and Dicamba
Critical Support by Lab
Perspective of Inspector

3. Reasons for collecting samples
Complaint Investigations (frequent)
Establish a line of forensic evidence to support or refute the allegation/s
Product Quality Assurance (infrequent)
Verify integrity of pesticide formulations in the channels of trade

4. Types of samples typically collected
Formulation samples at production or repackaging facilities
Liquids, dry, granules, wettable and insoluble powders, etc.
Aerosols and gases are rare, typically go to EPA lab
Residue samples which are part of an complaint investigation
Plants, soil, water, clothing, swabs, animal material, etc.

5. Sampling Decision-Making (the ‘why’ behind the type of sample collected)
Formulations are collected to determine product is within range of label guarantee
Residue samples are collected to establish evidence of a misapplication, or determine causes were related to symptoms or damage observed

6. Examples of Residue Samples
Plant material is the most frequently collected and analyzed

7. Examples of Residue Samples
Contaminated soil
Bees, honey, wax, wood, swabs
Water
Treated soil

8. Examples of Residue Samples

9. Sampling Protocols and Dicamba

10. Old School vs. New School (i.e. pre-dicamba and now)
Before dicamba sampling was used to:
Establish drift gradient
Determine toxicity
Estimate residual life
With dicamba, sampling is used to:
Determine presence of absence of chemical

11. Lab Involvement
It’s a two-way street: Pesticide programs need the lab to provide reliable, defensible sample analyses to prosecute cases and defend allegations.
At the same time the lab needs field inspectors to follow established procedures in order to adhere to QAQC requirements.

12. Inspector’s Perspective
How much material is needed for any particular sample media?
Plant = 1 lb?
Soil = 1 pt?
Water = 1 gal?
How are the samples prepared and extracted?
Are plants washed, chopped or ground up?
It could make a difference in what is sampled and how it is collected

13. Inspector’s Perspective
Does it matter what kind of plants are collected?
Evergreens vs. deciduous
Does soil need to be dry or can wet/muddy pass?
What about freezing vs. ambient temp?
Special techniques for swabs?
Some say wiping, others say dabbing or blotting

14. Inspection Examples Driving to inspection June 5, 2017
Spotted application equipment along highway backed up to reuse pond
Stopped to speak to applicator, collected water and soil sample

15. Lab Report: Soils

16. Lab Report: Water

17. Inspection Example Dept. of Aeronautics Inspector reported to NDA
“something just didn’t look right”
I investigated and found two aerial applicators circumventing their mix/load containment
The facility was built before 1993, when state containment came into effect

18. Inspection Example

19. Inspection Example
Waste Water
Soil

20. The Bigger Picture
Those red circles? They’re city water wells

21. Take-Home Message
State Pesticide Programs really need strong lab support
Labs can help advise field staff and managers on type and amount of samples for intended analysis
Don’t be afraid to let managers know if something needs to be changed, their programs rely on QAQC consistency