Climate Change,  Featured,  Food Supply,  Global Changes,  Global Threats,  Science

Global Threats: The Spread of Crop Pests

By Roberta Attanasio

Credit: Nicholas A. Tonelli, licensed under the Creative Commons Attribution 2.0 Generic license.

One of the major global threats to food security is the current spread of crop pests, unintentionally moved by human activity across world regions at unprecedented rates.

Crop pests include viroids, viruses, bacteria, oomycetes, fungi, nematodes, and insects. In the past, this spread was limited by physical barriers such as mountains, seas and deserts. However, such natural limits are now bypassed because of the rapid increase in international and intercontinental agricultural trade.

To date, more than 12,000 alien species have been documented in Europe by DAISIE (Delivering Alien Invasive Species Inventory for Europe), a unique three-year research project involving more than 100 European scientists and funded by the European Union. Many of these species are insects.

Indeed, it seems Europe has already been invaded by over 1,000 insects, including some of the most invasive species, such as the Tobacco Whitefly (Bemisia tabaci), the Western Corn Rootworm (Diabrotica virgifera) and the Colorado Potato Beetle (Leptinotarsa decemlineata).

What are invasive alien species? According to the International Union for Conservation of Nature, invasive alien species are animals, plants or other organisms introduced by man into places out of their natural range of distribution, where they become established and disperse, generating a negative impact on the local ecosystem and species.

Several factors contribute to the spread of invasive alien species. Border controls form the last line of defense against these invasions – inspectors intercept and stop consignments that are contaminated with harmful alien species. Insufficient border controls may lead to increased spread. Results from a study entitled “Gaps in Border Controls Are Related to Quarantine Alien Insect Invasions in Europe” and published last year in the scientific journal PLOSone, suggest that European countries with gaps in border controls are subjected to invasion by higher numbers of insect pests.

Although spread of crop pests is facilitated primarily by human transportation, increasing concerns are related to the effects of climate change — climate change allows the establishment of pests in previously unsuitable regions.

Rice blast symptoms on rice stalks
Credit: Donald Groth, USDA Forest Service,

Indeed, results from a new study entitled “Crop pests and pathogens move polewards in a warming world” (published yesterday in the scientific journal Nature Climate Change) indicate that global warming is resulting in the spread of crop pests and pathogens towards the North and South Poles at a rate of nearly 3 km a year.

The study is based on the analysis of published observations collected over the past 50 years. It examines the distribution of 612 crop pests and pathogens to conclude that their movement north and south towards the poles, and into previously un-colonized regions, corresponds to increased temperatures during that period.


Daniel Bebber, lead author of the study, said: “If crop pests continue to march polewards as the Earth warms, the combined effects of a growing world population and the increased loss of crops to pests will pose a serious threat to global food security.”


Spores of the rice blast fungus
Credit: Donald Groth, USDA Forest Service,

An example of pests that impact major world crops are the rice blast and wheat blast. Rice blast is a devastating disease caused by the fungal pathogen Magnaporthe oryzae. It results in lesions found on all parts of the plant, including leaves, leaf collars, necks, panicles, pedicels, and seeds and costs an estimated $66 billion in annual losses worldwide.

The Department of Plant Biology (The Ohio State University) reports that, in an alarming development, wheat blast, caused by a related fungus, Magnaporthe grisea, has emerged in South America and, recently, has been detected in Kentucky.

What are possible solutions to these problems? At the local level, crop diversification is one of them, as it slows down the spread of pathogens and pests. A survey published in the March 2011 issue of the scientific journal BioScience highlights multiple instances of farmers succeeding in protecting crops (such as rice and other cereals, alfalfa, and coffee) from outbreaks of pests and related disease often associated with climate change.

The farmers switched from growing a single variety of crop to growing a broader range of species or varieties, either at the same time or in rotation. An additional approach to crop diversification involved the introduction of structural variety into uniform fields. Fortunately, farmers have now increasing access to crop modeling techniques that can evaluate when a given adaptation technique might provide benefits.

However, climate change is an ongoing and extremely complex process. Old and new environmental problems related to the spread of crop pests can only be effectively tackled at the international level by developing new paradigms – paradigms that must overcome the challenges deriving from the different needs of countries and regions and from their different ability to develop and adopt new tools and strategies.



  • Cynthia Rose

    When I think of invasive species, I tend to think of barnacles and things that are more water oriented. It makes sense that there would be a number of animals and insects that could be introduced on land as well though. I wonder if my garden has had any trouble with this problem in the past?

  • SJ

    I think it is so interesting that people have been commenting indirectly on the pros and cons of GMOs. In line with this discussion would also be a risk assessment of GMOs as they relate to the immune system. In developed countries, there has been more of a push to use GMOs for many of the reasons mentioned in your comments. Additionally, developed countries have the technology available to produce GMOs for the public. However, I think it is important to determine if these organisms have the ability to induce an immune response that could be more harmful than beneficial to the public. This study ( has determined that GMOs do have the ability to cause an allergic reaction. Allergic reactions as a harmful con to the use of GMOs would probably need several more years of study as the use of GMOs is relatively new.

  • Andrew R

    I know that solutions were mentioned to address the issue at the local level like crop diversification and modeling. I am wondering, how effective would those methods be in a country like the US when subsidies are given to farmers to grow a particular crop. I use that to lead into the issue of using pesticides to combat these pests since it would be an economic way to handle the problem. Would the benefits of pesticide outweigh the risks? Pesticides have been getting “safer” as we move forward, but there have been instances of farmers reverting back to pesticides with arsenic since it was more effective. Arsenic was phased out due its cancerous causing nature, but the effects from heavy use up to the early 20th century is still with us causing the FDA to state that the levels are low enough to not cause any worry. However, a study was conducted a few years ago that found that Low-Dose Arsenic Compromises the Immune Response to Influenza A Infection in Vivo ( With that in mind, more should be done to protect the populous, whether it be having stricter border protection to implementing ways to slowdown global warming to using GMOs.

  • G Jose P-G

    South American farmers are limited to classical method of controlling vectors. For example Argentina being one of the more developed countries in the South Americas still relies on the use of pesticides for their soy bean farms. In Cordoba Argentina, which lies in the center of the country, the use of pesticides has raised to the point of court hearings in 2012. Victims of unusual health effects and miscarriages blame chemicals used in the soy bean farms ( This court ruling is controversial, as soy bean is the backbone of Argentina’s economy and has had little to no change in pesticide regulations since its first implementation on crop in the mid 20th century.

    Argentina, as well as many others like it, is limited to the forms of vector control. The improper use of pesticides leads to rise in toxic levels in the food and water supply. Mapping larval habitat, monitoring adult activity of vectors and educating farmers of innovative alternative methods could potentially be the best way in order to keep pests at bay. Economic evaluation should be taken into consideration when implementing vector control strategies. Crop rotation and growing a broader range of species varieties could also be a simple, but yet cost efficient and effective solution.

    • Mira

      G-Jose P-G,

      It is very unfortunate as the impact of pesticides is greater towards the unintended targets as it reaches a different destinations such as water, air, the food that we eat, and worse us as human than the targeted species. Different laboratories findings support that pesticides can cause health problems, such as birth defects, nerve damage, cancer, and so on. Even worse, some pesticides are found to be contribute to the depletion of the ozone layer, a study performed by the Environmental Protection Agency (

      As an originator of a third world country, I may assure that many users in such countries are inadequately informed about the short and long term effects of pesticides that they use.
      Also, with almost no regulations, there is no corrective measures as opposed for instance to organization such as the Federal pesticide program here in the US that ensures that the pesticides can be used with a reasonable assurance of posing no harm.
      So, I agree when you say: “that Crop rotation and growing a broader range of species varieties could also be a simple, but yet cost efficient and effective solution”. However, the mentioned economic evaluation is a little unclear.

      • G Jose P-G

        I’m very aware that many government agencies in third world countries cam be inefficient, corrupt, and uninterested to make a difference in the people’s lives. When I say economic evaluation needs to be taken into consideration I am refereeing that one model strategy cannot be used for all situations, especially if it is a first world solution. For example, a first world solution would be research for the latest preventive pesticide regulatory method. This form of thinking cannot be transposed onto a third world country, because of lack of regulations in the developing country or simply because of the cost of the program. We must also consider that developing countries exist in almost all ecosystems of this planet, with different geological terrains, abiotic, biotic and different social-economic factors. Discovering a ‘one solution fits all’ scenario is impossible. My ideal solution is to find cost efficient and effective alternative strategies that can attack different problems, without the use pesticides. This could be controlling vectors like mosquitoes. Solutions like crop rotation, diversification and modeling could be the best solution. In controlling mosquito vectors that harm crops, countries can also control the vectors that affect humans. This could guaranty a vibrant economical force for developing countries.

  • Stefon G

    Crop pests have been a major concern for global agriculture and due to global warming and the increase in human population, its only getting worse. We sometimes underestimate the effects that our actions have on this planet. Pollution, deforestation, and human expansion are all causing the migration of local pests into foreign environments and are problems we need stop if we want to win this war against pests. I agree with you that modern day transportation is contributing to the spread of pests in distant environments, but we can best tackle this issue by ensuring that we carefully sterilize foods and other items that are being transported from one area to another. Interestingly, the implications of using biotechnology to fight off crop pests are becoming extremely popular. Farmers are using genetic modified crops to fight off pests. One example is Bt-corn, which is a genetic modified corn that produces toxins that are harmful to the bacteria Bacillus thuringiensis. But my major concern with using genetic modified organisms (GMOs) as food source is that the long term effects are unknown. I personally believe that GMOs and the foods that we eat are linked to the increase in cancer related cases. So the question becomes do we continue to use GMOs to fight off crop pests without knowing the long term effects, or do we control the pest population by minimizing our impact on this world? I go with the latter.

    • Samantha S.

      I agree that the use of genetically modified organisms (GMOs) has had a positive impact on the crop industry but the impact it has on the health of consumers has yet to be established and that in itself is frightening. Our species prides itself on the constant technological advances we regularly produce but almost never think about the possible negative consequences of those actions. I definitely understand the driving force behind the production of GMOs from a monetary standpoint but the well-being of the consumer should always trump profit margins.

      The practice of “crop diversification” is definitely a step in the right direction but I also think that a more stringent screening process by border control needs to be implemented in all countries. In addition, with the seemingly constant spread of crops globally it may be worth it for many countries to tailor their crop production based on in pest currently present, i.e. produce crops uneffected by the pests present at that time.

      • BK12

        Interesting points brought up here. I wanted to chip in by finding out how have things like GMOs have modified the human gut bacteria that live in symbiosis with humans, and how has this modification impacted our bodies ability to handle molecules that we else could not properly breakdown. I feel like the consequences of the topics presented above have the potential to permeate all aspects of healthcare. Asides from this, I am left wondering how the evolution of crop pests will impact medicine. Lastly, even with the amount of knowledge and education that we garner, will we ever reach a point to where things like this will become more noticed. there are millions of mouths to feed, and for this very reason Need will to a certain extend trump what may be “right”. Personally I think sacrifices will always have to be made. The rate of planet decay as a result of global warming is astounding. In the end we may not only end up losing natural treasures but also ourselves. But I do believe in medicine and science. Perhaps its not too late.

        • chelton

          In response to your ideas about gut flora, I would like to add some information about Monsanto’s Roundup. Recently, the EPA has increased the allowable concentration of glyphosate, the active herbicide found in Roundup, for genetically engineered crops that are common in the Western diet. These include oilseed crops of flax, soybeans, and canola. The EPA recognizes harmful health effects from exposure over the allowable levels, particularly with kidney and reproductive damage, but they do not find adequate evidence that glyphosate is carcinogenic. The EPA technical fact sheet is linked here. Monsanto boasts of the “proven crop safety” of glyphosate on its website, and has been cited in stating the safety of glyphosate’s mechanisms of action in various formats. Their claims are based on the shikimate pathway mechanism that glyphosate uses to effect plants, not animals. However, the problem lies in the fact that this pathway does affect microorganisms. Dr. Samsel and Dr. Seneff explore the implications of this fact in their study regarding the effects of glyphosate on modern diseases. In this study, they find this pathway disrupts normal gut flora which leads to inflammatory diseases of the human immune system. Furthermore, the glyphosate enhances the damaging effects of environmental toxins and chemical residues ingested through food. The study continues to suggest both of these factors have consequences of many prevalent diseases related to the Western diet, including obesity, diabetes, and possibly some forms of autism. It seems there should be some more research done on this quite prevalent herbicide glyphosate to limit the adverse effects associated with its use.
          Samsel A, Seneff S. Glyphosate’s Suppression of Cytochrome P450 Enzymes and Amino Acid Biosynthesis by the Gut Microbiome: Pathways to Modern Diseases. Entropy. 2013; 15(4):1416-1463.

  • Claudette

    Hogweed is creating a lot of problems in Europe. It comes from North America and moved to Europe through contaminated farm tools and bird feed. It causes damage. Plus, in Hungary, a lot of people are allergic to it. Just an example of invasive alien species.

Leave a Reply

Your email address will not be published. Required fields are marked *