Neurotoxin to be sprayed on Washington oyster beds

B. McPherson

Never forget the law of unintended consequences
Washington State has given the oyster harvesting industry the go ahead to spray about 2000 acres of sea bed with imidacloprid to kill burrowing shrimp. Imidacloprid is a neurotoxin that particularly affects invertebrates(animals without backbones).

The state department of ecology has issued permits to spray the mudflats of Willapa Bay and Grays Harbor. The stated reason is to reduce the population of burrowing shrimp. They are also known as ghost shrimp. The two areas that are to be sprayed with the pesticide are important oyster producing areas. The annual revenue is over US$60 million per year.

The shrimp are feeders of small particles and given a high enough population can compete with other plankton eaters for resources. Burrowing shrimp dig in the intertidal mud flats almost constantly and kick out sand and other detritus. The sediment can cover the very young oysters(spat), suffocating them.

Imidacloprid is the most widely used pesticide in the world. Bayer Crop Science was the inventor of this neurotoxin, but the patent protection has run out so many other companies are now free to make copies.

The pesticide is not without controversy. It is a systemic poison which means that when it is sprayed on plants, the plants take it up into their cells and become poisonous. Those animals that are without backbones – shrimp, bees – are extremely sensitive to the neurotoxin. However it can damage fish which are slightly affected by it, birds which are vulnerable to it and humans exposed can develop troubling symptoms.

The spraying of mud flats will be a novel use of the pesticide. In the past the pesticide carbaryl was used to control shrimp numbers. It is now banned. The oyster growers have tried to control the shrimp numbers by dynamiting their burrows and in another failed attempt, spread a thin layer of cement on top of their burrows. The idea was to suffocate them but the creatures made new holes before the cement hardened.
Washington State Dept. of Ecology                

National Pesticide Information Center(Oregon StateUniversity)                               

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