K.L. Heong, International Rice Research Institute, Los Banos, Philippines.
The International Business Times (IBT) on 28 December 2013 named neonics research as one of the top 10 most amazing discoveries of 2013. Scientists discovered the toxic effects of several neonics at sub lethal doses to affect and threaten bees, aquatic fauna, bird fauna and human health. This has led to the banning of 3 such products, imidacloprid, thiamethoxam and clothianidin in European agriculture by the EU but these products are commonly used in Asian rice production. Since hymenopteran parasitoids, closely related to bees are important providers of natural control ecosystem services in rice ecosystems, these pesticides will also threaten rice production by inducing more planthopper pest outbreaks . A study by Italian researchers, published by the Proceedings of the National Academy of Sciences of the United States of America on October 21, 2013, PNAS vol. 110 , demonstrated that neonicotinoids disrupt the innate immune systems of bees, making them susceptible to viral infections to which the bees are normally resistant. Neonics are now “branded” as the new DDT.
Besides threatening pollination and biological control ecosystems services, impact of the neonics are worse than we had thought. A report published in March 2013 commissioned by the American Bird Conservancy “The Impact of the Nation’s Most Widely Used Insecticides on Birds” revealed the offsite damages to bird fauna. A tiny grain of wheat or canola treated with the neonicotinoid, imidacloprid, can poison a bird. As little as 1/10th of a corn seed per day during the birds’ egg-laying season will affect reproduction. Also published in 2013 is a paper quantifying the impact of neonicotinoids on the aquatic fauna.
Neonicotinoids are a group of neuro-active insecticides chemically similar to nicotine. These chemicals were developed for market because they show reduced toxicity compared to organophosphate and carbamate insecticides. Most neonicotinoids show lower toxicity in mammals than in insects. The neonicotinoid imidacloprid is currently the most widely used insecticide in the world and others with similar modes of action include acetamiprid, clothianidin, imidacloprid, sulfoxaflor, nitenpyram, nithiazine, thiacloprid and thiamethoxam. Imidacloprid has been the main insecticide used in rice in China for more than 10 years and most rice pest species had developed multi-fold resistance and the insecticides was removed from the rice market. These insecticides exert similar excitatory effects on both insect and mammalian nAChRs and thus can adversely affect human health, especially the developing brain and harm the brain of the unborn babies. The New York Times on Dec 18 2013 reported that European food regulators recommended further restrictions to the use of neonics because of their threats to human health.
China is the largest producer of neonicotinoids and when these products are withdrawn from the domestic market because of resistance it is likely that the neonics will find new markets in SE Asia, Africa and South America. In rice production the use of neonics is likely to increase rapidly although high resistance has already developed. The ban of neonics in European agriculture will also impact on increasing use of neonics in this part of the world. Since pesticide distribution and marketing is weakly controlled – “house with no roof” in most of these countries, the spread of neonics can be rapid and widespread posing threats to human health, bees, aquatic fauna, bird fauna and rice production through inducing pest outbreaks in Asia. There is urgent need to strengthen pesticide management regulatory systems to curb some of the undesirable impacts.