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Insecticide, the fall armyworm, and maize in Mexico

From the comfort of a desk, looking at a computer screen or the printed page of a newspaper, it is very easy to ignore the fact that thousands of tons of insecticide are sprayed annually.

Consider the problem of the fall armyworm in Mexico. As scientists and crop advisors, we’ve worked for the past two decades trying to curb its impact on corn yield. We’ve tested dozens of chemicals to gain some control over this pest on different crops.

A couple of years ago, we were comparing information on the number of insecticide applications needed to battle this worm during a break of a technical meeting. Anecdotal information from other parts of the country got into the conversation. Some colleagues reported that the fall armyworm wasn’t the worst pest in a particular region of Mexico and it was easy to control with a couple of insecticide applications. Others mentioned that up to six sprays were necessary in other parts of the country. Wait a second, I said, that is completely ridiculous and tremendously expensive to use so much insecticide in maize production.

At that point we decided to contact more professionals throughout Mexico and put together a geographical and seasonal ‘map’ of the occurrence of corn pests and the insecticides used in their control. Our report was compiled doing simple arithmetic and the findings really surprised us: a conservative estimate of 3,000 tons of insecticidal active ingredient are used against just the fall armyworm every year in Mexico. No wonder our country has the highest use of pesticide per hectare of arable land in North America.

Spodoptera frugiperda, fall armyworm. Photo courtesy of Marlin Rice.
Spodoptera frugiperda, fall armyworm. Photo courtesy of Marlin Rice.

Mexican farmers are stuck on what has been called ‘the pesticide treadmill.’ The first insecticide application sometimes occurs at the time that maize seed is put in the ground, then a second one follows a couple of weeks later, then another, and another; this process usually involves the harshest insecticides, or those that are highly toxic for the grower and the environment, because they are the cheapest. A way of curtailing these initial applications can be achieved by genetically-modified (GM) maize that produces its own very specific and safe insecticide. Not spraying against pests in the first few weeks of maize development allows the beneficial fauna (lacewings, ladybird beetles, spiders, wasps, etc.) to build their populations and control maize pests; simply put, it enables the use of biological control. The combination of GM crops and natural enemies is an essential part of an integrated pest management program — a successful strategy employed all over the world to control pests, reducing the use of insecticides, and helping farmers to obtain more from their crop land.

We have good farmers in Mexico, a great diversity of natural enemies of the fall armyworm and other maize pests, and growers that are familiar with the benefits of using integrated pest management in other crop systems. Now we need modern technology to fortify such a program in Mexican maize.

Mexican scientists have developed GM maize to respond to some of the most pressing production needs in the country, such as lack of water. Maize hybrids developed by Mexican research institutions may be useful in local environments (e.g., tolerant to drought and cold conditions). These local genetically-engineered maize varieties go through the same regulatory process as corporate developers.

At present, maize pest control with synthetic insecticides has been pretty much the only option for Mexican growers. They use pesticides because controlling pests is necessary for obtaining a decent yield, not because they are forced to spray them by chemical corporations or for being part of a government program. This constitutes an urgent situation that demands solutions. There are a few methods to prevent most of these applications, genetic engineering being one of them. Other countries have reduced their pesticide use by 40% due to the acceptance of GM crops. Mexico, the birthplace of maize, only produces 70% of the maize it consumes because growers face so many environmental and pest control challenges, with heavy reliance on synthetic pesticides. Accepting the technology of GM crops, and educating farmers on better management practices, is key for Mexico to jump off the pesticide treadmill.

Image Credit: Maize diversity. Photo by Xochiquetzal Fonseca/CIMMYT. CC BY SA NC ND 2.0 via Flickr.

Recent Comments

  1. Joe Funderburk

    I am having difficulty with the argument being made here. ultimately the fall armyworm will develop resistance to the bt crops if it hasn’t already and the insecticide treadmill continues. aren’t there serious risks to hybridization to important corn germplasm in Mexico?

  2. Carlos Blanco

    Joe: maize production in Mexico has been in an insecticidal ‘treadmill’ for many decades; that is what the report is all about, more than 3,000 tons of insecticidal active ingredient are applied annually; that is almost half a kilo per hectare. In my opinion something should be done to reduce this high use of insecticide. Bacillus thuringiensis-expressing corn may be one option to make a significant decrease.
    Your concern about the development of resistance to Bt is a justified one, something that has been documented recently in several regions where this type of corn has been grown for several years. But you should also realize that (1) in places where measures to delay the development of resistance have been implemented such as the United States, this technology has been proven effective for almost two decades, and (2) insects develop resistance to synthetic insecticides as well. For example, the tobacco budworm, another pest effectively controlled by Bt crops for the past 20 years, developed resistance to DDT in 14 years, to carbaryl in 10, to pyrethroids in 7 and to methomil in 5.
    Why should we necessarily believe that this technology won’t be more effective and last longer that the annual use of 3,000 tons of synthetic insecticides? Do we know that these insects are still controlled by these insecticides and they have not developed resistance to them as well?

  3. Serunjogi Emma

    Now, which is the right way to control fall Armyworm in maize?

  4. Derick wamboko1

    Now really what’s the specific one should we use even here in Uganda the same thing too resisting

  5. […] damage over a quarter of the crop field, systemic pesticides are recommended. Some scientists have noted in the past some excesses which have harmed farmers health and the environment without economic sense, alongside building […]

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