Insect Resistance

Overview
Today, pesticides are often used to help control insect pests, but with variable effectiveness and considerable expense. Even with effective control measures in place, countries with tropical climates such as India often have very severe insect damage that results in yield reductions of over 60%. Improving insect control strategies is important for several reasons. Decreasing the amounts of pesticides used in agriculture will benefit both the farm workers and the environment. In addition, we will need to dramatically increase agricultural production to meet the nutritional requirements of the additional two billion people expected to join us on Earth by 2050.

What is Insect Resistance?
Insect resistance refers to crops that either naturally or through genetic engineering are able to resist insect damage. Insect-resistant crops generally produce compounds that are toxic to insects that attempt to eat the resistant plants.

How have these crops contributed to sustainability?
Insect-resistant crops have become important tools for farmers, both large and small, around the world. Insect resistant corn and cotton have been credited with reducing the amount of chemical insecticides applied worldwide to those crops by 136.6 million kg, a 29.9% reduction. This has been particularly dramatic in cotton, where the use of Bt varieties has been integral to campaigns to eradicate major pests such as the pink bollworm from cotton-growing areas. In addition, the widespread use of insect-resistant corn in the US Midwest has reduced insect populations such that even farmers who do not use the Bt-containing varieties received economic benefits of over $4.3 billion since 1996 due to reduced insect pressure.

Specific Examples
Herbicide tolerance is the most common genetically engineered (GE) trait utilized in commercial agriculture today, with round-up ready soybean, corn, canola, cotton, sugarbeet and alfalfa occupying 62% of the global biotech area3. These crops broaden farmers' choices in weed control and could lead to practices that encourage insect and bird populations on farms, and promote agricultural sustainability through water, soil and energy conservation. The system consists of a non-selective herbicide and a corresponding herbicide resistant crop: A crop is made resistant to a particular herbicide. This is done by giving the crop a new gene or switching off an existing gene. The complementary herbicide is generally non-selective. It affects all sensitive plants by interrupting an essential metabolic activity. Concerns have been raised that if herbicide tolerant characteristics are transferred to weeds, this may make them more difficult to control, thus affecting biodiversity. In reality, such plants have no competitive advantage in the wild and could still be controlled by using an alternative herbicide. Another important benefit is that this class of herbicides breaks down quickly in the soil, eliminating residue carry-over problems and reducing environmental impact. Herbicide tolerant varieties are popular with farmers because they enable less complicated, more flexible weed control. 1. Kellogg, R.L., Nehring, R., Grube, A., Goss, D.W. & Plotkin, S. Environmental Indicators of Pesticide Leaching and Runoff from Farm Fields. USDA Natural Resources Conservation Service (2000). 2. Larson, S.J., Gilliom, R.J. & Capel, P.D. Pesticides in Streams of the United States--Initial Results from the National Water-Quality Assessment Program. US Geological Survey, Water Resources Investigations Report 98-4222. US Government Printing Office (1999). 3. James, C. Global status of commercialized biotech/GM crops: 2009 International Service for the Acquision of Agri-biotech Applications (ISAAA) Brief 41 (2010).