K.L. Heong, International Rice Research Institute, Los Baños, Philippines
Two recent headlines regarding the impact of pesticides on the environment and human health have raised some concerns. One describes the new links of fungicides, normally thought to have low effects on arthropods, linked to bee mortality and entitled it “… worse than you thought”. The other headline was about the death of children in India after eating an insecticide-contaminated meal in school. In Gandamal village, located 50 miles north of the Bihar state capital of Patna, 25 school children were killed and another 22 in hospital because of monocrotophos poisoning. Monocrotophos, an organophosphate neurotoxin, categorized as highly hazardous to humans, was a commonly used insecticide in rice in the 1980s and 1990s and continues to be used in some countries, like Laos, Cambodia, India, Philippines, Indonesia and Bangladesh. In the Philippines’ Masagana 99 program bottles of monocrotophos were “packaged” with rice seeds and fertilizers for distribution (Heong and Schoenly 1998). Similarly the Bimas rice intensification program in Indonesia also distributed monocroptophos with fertilizers as necessary inputs.
The Patna tragedy underscores the poor and unregulated conditions surrounding pesticide distribution, sales, storage, packaging and use in many Asian countries. Apparently the contamination came from cooking oil stored in a bottle previously used to contain monocrotophos. In 2005, a hundred school children in Bohol, Philippines were also poisoned by cassava sweets contaminated with a carbamate insecticide. Last year two tourists died from chlorpyrifos poisoning used for bed bug control in a hotel. Chlorpyrifos, a highly toxic neuro poison, remains a popular insecticide in Asia’s rice production. Many other poisoning cases remain unreported. Weak pesticide distribution and marketing regulations is one of the root causes of such negligence and tragedies.
Besides reports of acute poisoning, many of the neurotoxic insecticides in sub lethal dosages can cause brain damages in insects, mammals, birds as well as humans. There are now pieces of scientific evidence linking some insecticides to Alzheimers, Parkinson’s diseases, ADHD, low IQ and autism.
Three neonicotinoid insecticides were banned for use in Europe early this year. New links of pesticides causing bee decline are recently being discovered. In a Plos One paper Dr Petti and his colleagues showed that bees that consumed pollen with high fungicide loads had higher probability of infection by a gut pathogen, Nosema ceranae. Fungicides often thought to be rather safe to natural enemies and bees tend to increase the susceptibility to secondary infections by pathogens. More information on bees and pesticides trickle in weekly and a summary analysis of these can be obtained in BUZZFEEDS. A scientific review of neonicotinoids, bee disorders and the sustainability of pollinator services is now in press. Click here for PDF.
Secondary pests, such as the planthoppers and leaf folders are often induced by insecticides. One of the main causes of the recent series of outbreaks in Thailand and Indonesia was insecticide misuse (Bottrell and Schoenly 2012) as we see ”history repeating itself” . Impact of insecticide to rice herbivore – predator relationships research done at IRRI is summarized in Heong and Schoenly (1998) .
Responding to the crisis, the Thai government together with IRRI and the private sector launched a campaign to stop the use of two BPH resurgence causing insecticides, cypermethrin and abamectin, from rice. The campaign brought about awareness and changes in farmers’ beliefs and practices. A recent research by Dutch scientists showed that neonicotinoids, popular insecticides in rice, can have high effects on the aquatic invertebrates. In rice ecosystems, these invertebrates are important predators providing invasion resistance services that regulate the invading planthopper adults. In the US scientists found that imidacloprid, another popular insecticides used in rice, can cause outbreaks in spider mites in elm trees. Thus, increased use of imidacloprid in rice can increase rice fields’ vulnerability to planthopper outbreaks.
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. These concerns are also reflected in a letter to Science from China by Zeng et al.
Economists have raised issues regarding farmers’ low productivity gains from insecticide use and when health costs are factored in, farmers often suffer losses. In the 2011 document of FAO entitled “Save and Grow” paving a strategy towards sustainable intensification of crop production, it stated that “Most tropical rice crops require no insecticide use under intensification”. This was derived from IRRI research that concluded that “insecticides are not needed, rather than they are and pests need to be re evaluated and proven guilty before insecticide use is to be contemplated”. The current insecticide use in rice deviates widely from these research findings and when coupled with the heavy environmental and health penalties to farmers and the public, researchers and policy makers need to re-examine the merits of applying insecticides at all in rice production.