Pest-Resistant Crops

Many insects are herbivores, meaning they eat plants. Some pierce the stems or leaves to suck out plant juices. Others chew parts of or consume whole leaves and flowers. Some feed on roots, while others eat fruit.

In addition to directly consuming plants, insects also act as vectors of plant pathogens, spreading bacterial or viral infections among crops. This can lead to plant decay and yield losses. In monocultures, where a single type of crop is grown, these losses can be monumental.

To combat insect pests (as well as weeds and pathogens), farmers use synthetic pesticides.

Drawbacks to synthetic pesticides

The use of synthetic pesticides has negative consequences, including resistance in some pest species, decreased populations of beneficial insects, and health and environmental problems. This has created an urge to adopt more environmentally friendly pest control strategies.

Alternatives to synthetic pesticides

Efforts in this arena include biological control, mechanical control, crop rotation, and companion planting. Pesticides have been produced using ingredients from naturally pest-resistant plants, such as tobacco. Work on these botanical pesticides is ongoing. Another alternative to synthetic pesticides is pest-resistant crops. 

Pest-resistant crops are plants that have been genetically modified to produce their own protection against bugs. This protection is made possible by the genetic combination of the plant’s DNA with insect-resistant genetic material.

One example of this type of genetic engineering involves adding genes from the soil bacterium Bacillus thuringiensis (Bt). Bt naturally produces insecticidal proteins. Bt crops have been successfully grown in the U.S. since 1996. They are effective against a wide range of damaging pests common in agricultural crops. 

Effect of Bt crops on pests

Around 10,000 species of insects affect crops worldwide, with different pests causing damage at different life stages.

Most insects have 4 life stages: egg, larva, pupa, and adult. The larval stage is when most feeding occurs. Larvae usually feed on leaves, seeds, and fruits. However, some adults that feed on plant fluids can affect crops as well.

Bt crops are effective against insects because of specific proteins in bacterial spores. These proteins release toxins that attach to cells on the inside surface of an insect’s gut. The toxins cause insects to stop eating. They also destroy the cells they bind to, allowing bacteria from the gut to flow into the rest of the insect’s body, causing a fatal infection.

Different types of Bt toxins are infectious to different types of insects. For example, the kurstaki strain is active against some moths and butterflies, the israelensis strain is active against mosquitoes, flies, and gnats, and the San Diego strain kills beetles. 

Effect of Bt crops on humans

Since it kills insects, are we in danger if we eat plants containing Bt genes?

No. This protein only affects insects and is harmless to humans and other mammals, even in high doses. Eye and skin irritation as well as allergic reactions are possible, however. 

Effect of Bt crops on beneficial insects

Unfortunately, Bt can also affect beneficial insects, such as honeybees.

And while it is toxic to butterflies, it is not typically found at dangerous concentrations in pollen, and butterfly caterpillars are not common pests in Bt crops. 

Benefits of pest-resistant crops

Annual losses caused by pests are huge. Even with modern pest control tools, the United Nations Food and Agriculture Organization estimates that pests directly account for the loss of 20-40% of global crops. Plant diseases, often spread by pests, cost an estimated $220 billion a year, globally.

Pesticides cost the global economy over $35 billion each year. Pest-resistant crops are not only good for agriculture, they also benefit the economy and contribute to food safety. Fortunately, many crops are available in pest-resistant varieties, including corn, cotton, soybeans, and potatoes.

The adoption of Bt crops results in less pesticide use, less overall need for crop management, increased yield, and savings due to reduced pesticide use.

With these genetically modified insect-resistant crops available commercially, the agricultural industry’s pest losses can be minimized.

This is possible without spending billions on pesticides that damage the environment, endanger farmers, and kill beneficial insects. However, there is evidence that some insects are developing resistance to Bt crops. Further research is required to maintain the protection of the major global food source that is our agricultural industry.

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