Exploring the Ozarks Outdoors: freshare.net

Insecticides Lead Aquatic Insects to Starvation

By Robert J. Korpella

First posted on 05-17-2013


Neonicotinoids are a class of insecticides that are chemically related to nicotine. These insecticides affect the nerve synapses of insects, and neonicotinoids are popular for their solubility in water. Plants absorb the chemical, which is often applied to the soil to reduce its chances of drifting through the air.

However, the solubility that makes neonicotinoids prized for controlling sap-sucking insects such as aphids, has adverse affects on other organisms such as honeybees and aquatic invertebrates.

The toxicity of neonicotinoids on bees has been known for some time, and the use of these insecticides is suspected as a contributing cause in the decline of bee colonies. Bees can consume the chemical through plant nectar. However, recent studies point out how lethal neonicotinoids are to aquatic organisms.

A Swiss study, conducted by that country’s Federal Institute of Aquatic Science and Technology, demonstrated how low, but continuous concentrations of neonicotinoids affected the behavior of freshwater shrimp. These aquatic invertebrates, also known as scuds, are found throughout Ozarks streams.

imageFreshwater shrimp are quick swimming organisms that are somewhat tolerant of pollution. They contribute to overall stream health by shredding food sources, enabling smaller organisms to feed on the debris. Scuds also serve as food for larger animals, such as trout and other fish species.

Imidacloprid is one type of neonicotinoid found in some insecticides. The study subjected freshwater shrimp to high concentrations of imidacloprid in short-term bursts, as well as a consistent flow of the chemical in low concentrations. Both scenarios mimicked rainfall situations after lands had been treated with the insecticide. Runoff readily carries the substance into streams.

High concentrations of the chemical flowing into streams for not more than a day had less of a harmful effect on scuds than lower concentrations that persisted for several days, or even a week or more.

The scuds that were transfered to clean water after short-term burst exposure recovered quickly. However, those that were exposed to constant, low concentrations of the insecticide starved to death in 2 to 3 weeks. The nerotoxin impaired the shrimp’s mobility and feeding behavior.

Conventional toxicity testing fails to demonstrate this slow starvation because those tests are not administered over several weeks time.  The results of this study also show how crucial seasonal factors can be, as insecticides may be applied several times during the months when insects are most prevalent.

You may want to check the ingredients of any insecticides you use around the house or farm. If the labeling indicates one or more of the following chemicals, it contains a neonicotinoid:

•  Acetamiprid
•  Clothianidin
•  Dinotefuran
•  Imidacloprid
•  Nitenpyram
•  Thiocloprid
•  Thiamethoxam

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