The Muddled Debate About Pesticide Use And GM Crops

Does the adoption of GM crops lead to more or less pesticide use?  This is a frequent topic of debate, but generally one that misses the point.  Both sides make the same erroneous assumption that all pesticide use is, by definition, a bad thing.  In fact, it depends on the particular pesticide in question, the reason it is being used, and the details of its application.  Most modern pesticides are extremely low in hazard to us or to the environment.  Both "sides" of the GM debate would do well to stop over-simplfying this issue.

What Biotech Can and Can't Do

In his recent speech expressing regret for his former role in the anti-GMO campaign, environmentalist Mark Lynas cited cases where biotech crops reduced the need for pesticide applications (e.g. Bt Cotton and Bt Maize).  The examples are quite positive from the farmer's point of view.  However, for crops with biotech insect resistance, pesticides remain an important and well regulated tool for farmers who still have to deal with many other pests for which there may never be a biotech solution.   The supporters of crop biotechnology need to maintain the perspective that biotech traits are simply one tool in the tool box.  There is no excuse for ignoring the science behind advances in pesticide risk management any more than for ignoring the science behind risk management for GM technology.

Putting "Increased Pesticide Use" Into a Global Perspective

Jason Mark recently posted a "rebuttal" to Lynas' speech on Earth Island Journal.  It relied on exactly the sort of "self referencing" sources that Lynas critiqued, but one argument struck me as sufficiently absurd to warrant a response:

"A peer-reviewed study published last year in Environmental Sciences Europe found that GM plantings in the United States led to a 7 percent increase in chemical spraying."

Seriously? A European publication expressing angst about an incremental change in US pesticide use on its major crops? Do they know about the intensive use of pesticides on crops in Europe? (see graph below).  Actually, it is the study by Chuck Benbrook of the Organic Center in the US which generates a seemingly large number until you consider that his model includes use on hundreds of millions of acres over 16 years).


Why do European farmers use so much pesticide?  The reason is simple: they have to deal with lots of pests!  As with farmers everywhere, those in Europe face insects, weeds, fungi, bacteria and viruses which, if uncontrolled, diminish the amount of food that they can produce.  They farm in a generally wetter climate, and so they need lots of fungicides.  Like any farmer, they use the highly regulated pesticide options available to them so that they can limit the damage from those pests.  If they didn't use those pesticides, they would be making inefficient use of their land and of other necessary inputs like fertilizers and fuel.  As it is, Europe imports a great deal of its food and feed (206 million metric tons for the top 20 commodities imported in 2010).  When European farmers use pesticides to be as productive as possible, they at least help to minimize that strain on the global food supply.

Putting "Increased Pesticide Use" Into Quantitative And Contextual Perspective

The 7% increase Environmental Sciences Europe cites as an offshoot of GM crops mainly involves a herbicide, glyphosate, which happens to have a benign profile in terms of toxicity to things other than plants.  The transition to glyphosate for "Roundup Ready"crops replaced the use of sulfonyl ureas, a class of herbicides which had extremely low use-rates.  Thus, the still modest glyphosate use rate of 22-44 ounces of product per acre represented a small increase in total "pounds on the ground." Ken Cook of the Environmental Working Group responded to Lynas with a post in which he describes these crops as being "slathered with chemicals."  The 44 ounce rate means that each liquid ounce is spread over an area of almost 1,000 square feet. The active ingredient is applied at less than 0.01 grams per square foot.  Somehow, that does not fit my mental image of "slathered."

The far more relevant point is that glyphosate tolerant crops represented a more practical alternative to mechanical tillage for weed control and enabled wider adoption of "no-till" farming.  That is a system which conserves soil moisture, prevents erosion, dramatically reduces nutrient and pesticide movement to streams and rivers, and reduces fuel use.  If biotechnology and herbicides can combine with sophisticated equipment to enable this sort of farming - all the better.

Bottom line, a biotechnology trait may decrease or increases the need for a pesticide.  There will also be many cases where the biotech trait has nothing to do with pesticide use.  There is no necessary good or bad linkage between these two categories of agricultural technology - both can serve to make crop production better.  Both are options that should be available to those who farm.

You are welcome to comment here and/or to write me at savage.sd@gmail.com.  My Twitter feed is @grapedoc

Sprayer image from North Carolina Crops

Eight Technologies Keeping A Carcinogen Out of Your Food

Safe, Tasty, Nutritious Almonds We Shouldn't Take For Granted

Sometimes we need to hear about things that are working well in our food system.  I'd like to describe a case where sound regulation and well-applied technology combine to protect us from a significant risk posed by a natural chemical called Aflatoxin - one of the most toxic and carcinogenic chemicals known.  Aflatoxin can contaminate a wide range of foods from maize (field corn), to peanuts, to cotton seed meal, to tree nuts (almond, walnut, pecan, pistachio), to wild collected nuts (Brazil nut), to dried peppers to various spices. It can even be in chocolate! For those that live in "The Global South" (or developing world), aflatoxin is one of the leading causes of illness and death - particularly through liver cancer.  If you live in the richer parts of the world, you may never hear about this toxin. Strict regulations, combined with a suite of technologies and testing protocols, do a very good job of protecting us from this threat.  I'd like to describe them, but first I need to talk about...

The Bad Guys In This Story

This threat of contamination involves a "conspiracy" between a fungus, an insect, and the climate.  Ok, its just biology, but it is still insidious.  Insects, particularly caterpillars, damage crops by feeding on them.  Certain species and strains in the fungus, Aspergillus, are able to infect parts of plants that are damaged by the worms.  The fungus produces the toxin as a means of excluding other microbes from that damaged site.  For many crops (particularly maize,) drought or heat stress increases the susceptibility of the plant to this sort of attack.

Navel Orange Worm Larvae in a Nut

In some crops (particularly tree nuts), the insect and the fungus strike a mutually beneficial pact.

A caterpillar called the Navel Orange Worm actually transports the Aspergillus fungus with it when it feeds on developing fruiting structures of the nut tree.  This worm has a phenomenally effective P450 enzyme that detoxifies the aflatoxin to which it is exposed so that both partners are protected in their niche by the toxin.  These are formidable foes, but fortunately not insurmountable when the following technologies are deployed.

Technology 1: Analytical Methods

A number of companies have developed various analytical tools to fit various parts of the system.  Rapid, cost-effective, and robust tests are available that can be used by non-experts to exclude contaminated loads before they enter the supply at somewhere like a grain elevator.  Very sensitive and precise tests are available to check the end product to meet even the high EU standard for nuts of 2 parts per billion aflatoxin.  The Gates foundation is funding development of very low cost tests to extend this life saving capability to the developing world.

Technology 2: Orchard Sanitation

There is an important "low tech" component to managing this threat.  In nut orchards, the Navel Orange Worm overwinters in "mummies"- the damaged and colonized fruiting structures which tend to stay attached to the tree, unlike the healthy nuts which are shaken loose during harvest.  

Mummies (dark) left from the previous season harbor the Navel Orange Worm

It is very important for the growers to remove as many of the mummies as possible from the trees and to destroy as many as possible of those that fall to the ground.  Workers walk through the orchard with long bamboo poles to knock down as many mummies as they can.  In a recent study in Pistachios, it was determined that a threshold of 0.2 mummies/acre was desirable to keep worm populations low enough.  That would mean that between 99.965% to 99.977% of the nuts and mummies need to be removed by either harvest operations or subsequent sanitation.

Technologies 3 and 4: Insecticides and Mating Disruption

For the nut crops, the best strategy (in addition to doing the orchard sanitation) is to use two, well-timed insecticide sprays along with mating disruption - essentially putting out lots of sources of the Navel Orange Worm's mating hormone so that the males get completely confused and unable to find the females.

In a large scale, three year study (see graph above I made from their published data), the combination of insecticides and mating disruption provided the best control of the worms and thus greatly reduced the introduction of the fungus.

Technology 5: Biotechnology (Marker Assisted Selection)

Marker assisted selection is essentially conventional plant breeding except that the breeder knows which specific genes are being moved around.  This is a side benefit of decades of investment in better and better laboratory tools for biotechnology (used in plant and medical technology). As an example, it has been used by Syngenta to develop more drought tolerant corn, and that will potentially lower aflatoxin levels.

Aspergillus infection of corn like this can be prevented with insect and drought resistance traits

Technology 6: Biotechnology (GMO)

There is also a GMO drought tolerant corn from Monsanto that will first enter the market in 2013, and this should also help reduce aflatoxin.  The more dramatic effects are seen with insect resistant corn lines (available from several companies).  If the worms (European Corn Borers in this case), can't feed long enough to damage the ears of corn, then the Aspergillus can't follow and produce the toxin.  This was observed quite clearly last year.

Technology 7: Biological Control

One very cool strategy developed by USDA scientists is finding strains of Aspergillus which compete well at colonizing insect damaged plant tissues, but which don't make the toxin.  These are called "atoxigenic strains", and they are introduced into the field as pellets that sporulate and allow these benign strains to find their way to the plants.  Syngenta, is now offering this product as Aflaguard.  The combination of the biocontrol agent and biotech-based insect resistance proved to be a particularly effective combination for maize in the 2012 drought.





Technology 8: Fluorescence Detection

With crops like tree nuts or peanuts, there is one more step that can be taken to deal with infections that slip through the other control measures (remember there is an almost zero tolerance for this issue). Shelled nuts are carried, one-by-one, at high speed, down a conveyer belt past a source of light that has a wavelength that will produce fluorescence at another specific wavelength if Aspergillus is present on a nut.  If that signal is picked up with detectors, a perfectly timed puff of air knocks that nut off the line.  This is why I always prefer to buy shelled nuts because they typically go through this process.  This procedure is also commonly used for peanuts going into peanut butter and other confectionary uses.

A great deal of effort goes into minimizing risks associated with aflatoxin in our food supply.  Extending these sorts of protections to the developing world is not easy, but is a much needed change.

You are welcome to comment here and/or to email me at savage.sd@gmail.com.  You can also follow me on Twitter (@grapedoc).

Almonds image from HealthAliciousNess' photostream. Pistachio mummy image and Navel Orange Worm in nut image from the University of California.  Aspergillus infected corn image from Iowa State University. Biocontrol image from USDA-ARS