Saturday, May 30, 2015

Neonicotinoids pesticides

Recently, the word "neonicotinoids" as a group of insecticides appear frequently in various news reports because the concerns of their association with the increasing mortality rate of honeybees. Because of the potential impact on the pollinators including honeybees, neonicotinoids are at a stage of "near ban". High priority for conducting further risk assessment on neonicotinoids is given by chemical regulations agencies.

Let's have a closer look at neonicotinoids

As indicated by the name, neonicotinoids are related to nicotine.

Neonicotinoids is a group of pesticides most widely used in the world. The group includes






Neonicotinoids act on the central nervous system of insects. Neonicotinoids can bind to some receptors in the nervous system and prevent impulses transmitting between nerves. This biochemical action mechanism would make insecticides exposed to neonicotinoids unable to move and eventually die.

Neonicotinoids have high water solubility and break down slowly in soil. They are often applied to soil and be taken up by plants and provide protection from insects as the plant grows.

When developed, neonicotinoids were claimed to have low-toxicity to many beneficial insects, including bees. However,  toxic effects to bees and other beneficial insects have been realized recently. Bees and other pollinators expose to neonicotinoids through nectar and pollen where neonicotinoids are used in agriculture for pest control. Although the exposed levels are sub-lethal , they may impact some bees’ ability to navigate to flowers and nectar.

Despite some controlled studies, more information is still needed to link neonicotinoids to the bee colony collapse disorder and increased mortality rate of honeybees. However, to keep potential risk to bees and other beneficials low, Corn farmers in Ontario and Quebec are requested to use dust deflectors on their seed planters, and that the seed companies use a seed lubricant to minimize the dust that is emitted during planting.

References and more information:

Friday, May 29, 2015

Natural polychlorinated organic compounds produced by snow flee as predator repellent

A lot of organic pollutants posing negative impact on the environment and on human health are chlorinated. Well known chlorinated hazardous organic chemicals include the well known DDT, PCBs, HCB,  Mirex, Dioxin, etc. All of the 12 persistent organic pollutants (dirty dozens) initially listed in the Stockholm Convention for international regulations are chlorinated compounds. Many of the chlorinated compounds were used as pesticides.

Halogenated organic compounds are seldom found as natural products. Recently, researcher Schulz and colleagues in Germany found one natural chlorinated compounds from the snow flee, a winter-active species of springtail, produces unique polychlorinated octahydroisocoumarins to repel predators. Sigillin A, the active component with five chlorine atoms,  showed high repellent activity in a bioassay with predatory ants.

The snow flee is easily ignored as it is only a few millimeter long, just list some pallets of black pepper on the snow. But such tiny flees have their unique strategy to deal with their predators. They can synthesize their own pesticide Sigillin A to repel ants, spiders etc.

Snow flees are quite efficient at synthesizing Sigillin A. despite Sigillin A is such a complicated organic molecules. Sigillin A synthesized by a snow flee can be 0.2% of it tiny body weight.  It is still unclear whether Sigillin A is synthesized by snow flees themselves or by microorganisms in the body of a snow flee.

Effort has been make to synthesize this natural chlorinated in the lab. Chemists are looking forward to producing this natural chlorinated compound and use it for termite control.

However, natural generated does not mean it is environmental safe when synthesized and used in large quantity. It's environmental persistence, bioaccumulation potential, and toxicity needs to be carefully evaluated before large quantities is produced and used