Imidacloprid: a solution or an anathema?

A pesticide is any substance or mixture of substances used to destroy, suppress or alter the life cycle of any pest. A pesticide can be a naturally derived or synthetically produced substance.

In this modern age, the thought of food pesticides turns many consumers off. Pesticides have been used since Sumerian agriculture 4500 years ago, but its effects on people have only been documented for the last fifty to sixty years. The research and findings have generated enough awareness and disgust to propel the organic movement, a return to what's natural, though many consumers are unaware that organic farms still use pesticides. The difference is, the pesticides are certified organic.

When it comes to oyster aquaculture, consumers mostly regard the farming practice to be positive and sustainable because farmed oysters live and grow in their natural habitat and do a lot of good for the environment. Recently, however, news of a pesticide permit for Willapa Bay and Grays Harbor in Washington, the nation’s largest shellfish producing bay, has sparked outrage as the public learns of pesticide use in shellfish aquaculture for the first time.

The backlash caused the state to withdraw the pesticide permit approved last April, disappointing many Washington shellfish growers who were depending on it. So what’s going on? Why are Washington shellfish farms using pesticides?

A little background

Since at least the 1940s, the Pacific has been plagued with two native species of inedible burrowing shrimp. The shrimp feed by digging in the sediment, and in doing so, soften the sand and disrupt the structural integrity of the sediment causing shellfish to sink and suffocate. Eelgrass habitats that support other marine organisms are also affected because the sediment is too soft for roots. Once the shrimp take over, many of the tidal beds become useless as the shrimp get as dense as 400 shrimp per square meter.

Photo from Damian Mulinix | The Daily Astorian

Photo from Damian Mulinix | The Daily Astorian

The state recognized the damage caused by the shrimp and began testing various control methods. Carbaryl or Sevin, an insecticide, was approved in 1963 and was used until it was phased out in 2013 after carcinogenic effects were discovered. As water temperatures have warmed, the shrimp population has increased and without a way to control them, many commercial shellfishermen are watching the shrimp destroy their once productive beds that now look like moon craters.

The permit approved last April was for the use of imidacloprid, the most widely used insecticide in the world, even found in flea collars for pets. The dosage approved was 1/16th the dosage of carbaryl per acre, a highly diluted amount. Recent research, however, suggests imidacloprid may be responsible for the collapse of honey bees, and several countries have already restricted the use of such neurotoxins.

Photo From Steve Ringman | The Seattle Times

Photo From Steve Ringman | The Seattle Times

So should imidacloprid be permitted?

Arguments FOR imidacloprid

  • Imidacloprid is far safer than carbaryl and would be used in a smaller and highly diluted dosage applied by hand.
  • It would never be sprayed on oysters, only on the sediment before oysters are even seeded there months later.
  • It would prevent a worse case scenario of a 70-80% reduction of shellfish production – the bay currently yields about $35 million in product and is the economic backbone of Pacific County, employing many of its residents.
  • The insecticide does not kill the shrimp, but paralyzes it.
  • Burrowing shrimp is an invasive species destroying other parts of the ecosystem like eelgrass habitats and the estuaries.
  • Imidacloprid would only be sprayed in non-eelgrass areas with dense shrimp populations.
  • Many generational growers will lose their farms and not even be able to sell them because the flats are unproductive.
  • Imidacloprid is highly water soluble and has very low toxicity to fish even on an acute basis.
  • Bees do not frequent shellfish beds.

Arguments AGAINST imidacloprid

  • The burrowing shrimp are native species to Washington. The cultured gigas oyster originally from Japan is the invasive one.
  • There would be uncertain consequences to the aquatic ecosystem.
  • Because imidacloprid is highly water soluble, it shouldn’t be applied directly to water.
  • Although the imidacloprid paralyzes the shrimp, the shrimp eventually suffocate and die.
  • Imidacloprid is highly toxic to aquatic invertebrates, moderately toxic to small birds, and may affect other subsurface organisms.
  • If there is no light, imidacloprid will break down slowly in water in which the half-life of imidacloprid is about 1 year.
  • NOAA and U.S. Fish and Wildlife Service oppose the use of imidacloprid on ocean environments.
  • Pesticides can drift into neighboring farms of growers who refuse to use pesticides.
  • The use of pesticides make oysters seem less “natural” or “quasi-wild.”
  • We are changing the land and sea to better our human production needs.
  • If aerial application is allowed, there might be potential spray drift from the helicopter.
  • Potential confusion in public access areas treated by imidacloprid.

We summarized the main arguments from both sides above. Shellfish growers in Willapa Bay are just as torn as some growers are for and others are not.
 

What do you think?
Share your thoughts with us in the comments below.
 


Sources

Fact sheet for Willapa Grays Harbor Oyster Growers Association National Pollutant Discharge Elimination System (NPDES) Permit No. WA0039781; October 24, 2014

Willapa Desert: Key oyster bed abandoned as inedible shrimp take over; The Daily Astorian: http://www.dailyastorian.com/Local_News/20160805/willapa-desert-key-oyster-bed-abandoned-as-inedible-shrimp-take-over

Get out of the way and let oyster growers survive; The Chinook Observer: http://www.chinookobserver.com/co/editorials/20160809/get-out-of-the-way-and-let-oyster-growers-survive

Washington State Turns to Neurotoxins to Save Its Oysters; Bloomberg: http://www.bloomberg.com/news/features/2015-04-24/washington-state-turns-to-neurotoxins-to-save-its-oysters

Willapa Bay Oyster Farmers Ask State Again for Permission To Use Neurotoxin; KPLU: http://www.kplu.org/post/willapa-bay-oyster-farmers-ask-state-again-permission-use-neurotoxin

Can oyster farms make Puget Sound a little more wild?; Crosscut.com: http://crosscut.com/2016/06/can-oyster-farms-make-puget-sound-a-little-more-wild/

U.S. consumers across the country devour record amount of organic in 2014; Organic Trade Association: http://ota.com/news/press-releases/18061