Debunking Denialism

Fighting pseudoscience and quackery with reason and evidence.

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Mailbag: Ban All Agricultural Pesticides?


It is time for another entry in the mailbag series where I answer feedback email from readers and others. If you want to send me a question, comment or any other kind of feedback, please do so using the contact info on the about page.

There is a culture of fear and hate around agricultural pesticides. This is to some degree understandable, because pesticides have some risks. Large, chronic exposure can cause severe harm, thousands of people die from acute exposure to high doses and pesticides can kill non-target organisms and pollute groundwater.

However, there are also beneficial aspects with pesticides. If we let pests run amok, we would lose 50%-80% of the crop harvest and pesticides play a partial role in preventing such devastating crop loss. They can also reduce labor required to manage weeds and contribute to suppressing insect vectors for diseases (at least for a certain time until resistance develops). Extreme anti-pesticide activists also actively oppose replacing more dangerous pesticides with safer pesticides and using genetic modification to reduce pesticide use. Read more of this post

Why Rachel Parent is Wrong About Genetically Modified Foods

Rachel Parent

Rachel Parent is a Canadian 15-year-old anti-GM activist who wants GM foods to be labelled. In an independently organized TEDx event at Toronto, she held a talk regurgitating almost all popular anti-GM claims in under 15 minutes. She claims to have been interested in GM crops since she was 12, yet the “research” she did involved reading anti-GM websites, not scientific papers. It is great that young women are getting increasingly interested in science and scientific research, but deceptive misinformation is a poor substitute for scientific integrity. In reality, all of her claims are either wrong or misleading: BT is safe for humans and have been used in organic farming, all plants contain their own “bug killers”, GM technology has been used to save the papaya and make rice prevent vitamin A deficiency, GM crops does increase total yield, is associated with less usage of dangerous pesticides, GM crops do not harm beneficial insects, farmers are not sued by accidental cross-pollination and GM crops are as safe as conventional crops. Even the paper she cites as evidence for GMOs causing allergies does not even mention GM crops. This post goes into detail in explaining why Parent is mistaken.

BT toxin is safe for humans and has been extensively in organic farming

BT toxin is a substance that is produced by bacteria and is only dangerous to a certain group of insect pests. This is because of its high specificity: it requires an alkaline stomach environment (humans and other mammals have acidic), a specific protease that cleaves the inactive precursor into the active toxin, a specific receptor on the gut surface that triggers the rupturing of the stomach lining.

It has been used extensively in both conventional and organic farming for many decades by spraying bacterial spores on the plants surface. However, with the help of recombinant DNA technology, scientists have been able to insert the gene that produces this toxin into the plant itself. It is a method that we know is safe and that we know work.

Plants cannot run, therefore they contain their own bug killers

Although it might seem odd at first that plants contain their own bug killers. However, this is actually very common. Most plants are stationary with roots into the ground and so they are not able to run away from their predators. Instead, they have evolved means of protecting themselves by using poisonous secondary metabolites. Among these are the solanine in conventional potatoes, spinasterol in spinach and coumarin in carrots. These can have neurotoxic effects, interfere with hormonal signaling and cross-links DNA. So far from being weird, plants making their own bug killers is the norm. These substances, like BT, occur in very small concentrations of course, so they are not dangerous to humans.

GM technology as been used to save papaya and to prevent deadly vitamin A deficiency

Parent focus exclusively on the two most common GM applications in agriculture: herbicide resistance and insect resistance. However, she does not bother to discuss other applications, such as virus-resistant papaya or rice that have more vitamin A.

The papaya ringspot virus (PRSV) almost exterminated papaya farming in Hawaii, which represented the vast majority of papaya production in the world. Researchers were able to genetically modify those papayas to make them resistant, and thus prevent the papaya production from collapsing. In other words, one of the reason that we still have papayas today is because of GM technology.

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