Webinar Q&A: Biological pesticides - Approaches to Terrestrial Non-Target Arthropod Testing

Webinar Q&A: Biological pesticides - Approaches to Terrestrial Non-Target Arthropod Testing

In March, Dr. Michael Patnaude presented the webinar Biological Pesticides - Approaches to Terrestrial Non-Target Arthropod Testing, an overview of the commonly used terrestrial non-target species available for biological products following the 885.4340 guideline.

Read below for responses to questions asked during the audience Q&A.

Q: Is Smithers involved with any ring testing or OECD method development?
A: Not specifically for microbials, but Smithers has been involved in ring testing/OECD method development with solitary bees, bumble bees, and honey bees.

Q: How variable are the analytical recoveries generally? Is it possible to have consistent microbial content?
A: From the available studies, we haven’t seen too much variability,  CV’s averaging around 20%.

Q: How often sponsor request you to test monarch butterflies? How many studies you typically conduct per year?
A: Not often, the last monarch butterfly study before this one was about 17 years ago.

Q: Have you tried other diet additives like solvents or surfactants in the honey bee diets? Do these impact the microbials?
A: We have used solvents in honey bee diets, but not for microbials.  They may impact microbial survival and as such would benefit from diet trial work beforehand. 

Q: What are your biggest challenges you face with NTA studies and microbials?
A: Understanding all the required parameters and making sure they are represented in the protocol.

Q: How is 10-100x the field concentration determined?
A: It is based on the application rate and the dilution factor to determine the number of colony forming units (CFU’s)/mL and then applying the 10X or 100X safety factor.

Q: For the green lacewings tests, how much is the percentage of adult emergence using liquid diet for control treat?
A: Adult emergence averages around 60%, but as the larval exposure typically lasts at least 10 days there are robust data for risk assessment. 

Q: How much xanthan gum do you typically add to your 50% sucrose diets?
A: 0.15% xanthan gum is our typical target for 50% sucrose diet.

Q: In most cases for microbial pesticides is daily preparation required, or you can prepare once and freeze? The slides with rove beetle showed a bold statement that meat diet would be dispensed onto weigh paper daily and not prepared into frozen meat packets.
A: Daily preparation is the default unless diet trial work (or client provided information) demonstrates microbial stability under refrigeration or freezing.

Q: How do you account for toxic compounds that develop from heated co-formulants in heat attenuated test items groups?
A: If the co-formulant solution is available before the microbes are added during production, then this would be needed as a control if the co-formulants are toxic or suspected to be toxic when heated.  If this information is not available, preliminary testing could identify issues with heat-attenuated co-formulants.  A filtration control may also provide an appropriate control in this case if the microbe can be filtered out of the test material solution.  

Q: The focus in the EU is promotion of biologicals over chemical PPP's, do you foresee the US moving in the same direction?
A: I don’t see it happening in the same way.  The US has about twice the number of registered microbial products compared to the EU. This is likely due to an easier US registration process for microbials.

Q: Did you ever have observed effects of microbial products on Collembolans?
A: Of the microbial products tested here, we have not seen effects from microbial products on Collembola.

Q: What is your ecological reasoning for testing microbials collembola or earthworms? They naturally live on a diet of microorganisms, so any test item you give them would just be more food. I have never tested microbial pesticide where the test item group did not outperform the controls for both test species.
A: Collembola and earthworms already have available test methods (OECD 232, 207, 222). Beyond the characteristics that make them important to test traditional chemicals, the characteristic of eating microbials would make them very appropriate to test as they are likely to be exposed more than other organisms. 

Q: Carboxy methylcellulose may be suitable apart from xanthum?
A: I would agree that it would be worth exploring other thickeners such as CMC.

Q: How many tests precipitate 50% sucrose?
A: It seems to be common for separation of microbials in 50% sucrose.  Visual trials are important to establish suspension options in sucrose.

Q: How do you account for the clumping?
A: Heating or agitation techniques are some of the available options that may disperse clumps.  These methods would need to be worked out before testing begins.

Q: Are any of these organisms/methods especially difficult to work with?
A: None of the listed species are particularly difficult.  Most just take practice and experience.

Q: Aside from Honey bees, are there any seasonal limitations?
A: Most if not all the other non-target arthropods are cultured in laboratories such as lacewings and ladybird beetles and do not have seasonal limitations.  Solitary bees may be the only group that does. Some Osmia species are only available from about February to April.

Q: Some of the studies are <10-days. Has any work been performed to extend these?
A: Most of these tests were originally designed for a shorter duration than needed for microbials, but any tests could likely be extended to accommodate a longer duration.

Q: In reference to the Endangered Species Act (ESA), what insects used in testing may be potential surrogate species for the endangered insects?   
A: The following are examples of potential surrogates for representing some of the endangered insect species; 
  • Pink-spotted ladybird beetles as a surrogate for various endangered beetles (ground, tiger, burying, etc.)
  • Honey bees as a surrogate for the various endangered yellow-faced bees
  • Common eastern bumble bees as a surrogate for the endangered bumble bees (Franklin’s and Rusty patched)
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