Home Agriculture Bt Crops: To Plant or Not to Plant

Bt Crops: To Plant or Not to Plant

by Admin-Phmp
Published: Last Updated on

By Henrylito D. Tacio

Photos courtesy of BIOTECH and SEARCA

Scientifically, it is called Ostrinia furnacalis, but it is commonly known as an Asian corn borer. It is likely the worst pest insect on corn in the western Pacific region of Asia and one of the worst pests overall.

This insect can cause devastating losses in a cornfield. In the Philippines, losses of 20- 80% have been reported. In Taiwan, it has reached 95%. The moth larva feeds on almost any part of the plant, damaging the fruit when it bores into the ear to feed on the silk and kernels.

Asian corn borer is one of the pests that can be eliminated by Bt corn. Bt stands for Bacillus thuringiensis, a common soil bacterium so-called because it was first isolated in the Thuringia region of Germany. It produces a protein that paralyzes the larvae of some harmful insects.

Through genetic engineering, scientists have taken the Bt gene responsible for the production of the insecticidal protein from the bacterium and incorporated it into the genome of plants. As such, the plants have a built-in mechanism of protection against targeted pests.

Aside from corn, Bt is also introduced in cotton, poplar, potato, rice, soybean, tomato, and, more recently, eggplant. “The protein produced by the plants does not get washed away, nor is it destroyed by sunlight,” said a briefing paper published by the Global Knowledge Center on Crop Biotechnology. “The plants are protected from the insects round the clock regardless of the situation.”


Since Bt crops are able to defend themselves against pests, the use of chemical insecticides is significantly reduced. A study conducted by the United States Department of Agriculture showed that 8.2 million pounds of pesticide active ingredients were eliminated by the farmers who planted Bt crops in 1998.

“Aside from being effective against insect pests, Bt crops have lower incidences of opportunistic microbial pathogens, such as the fungus Fusarium,” the briefing paper said. “This fungus produces mycotoxins that can be deadly to livestock and also cause cancer in humans.”

The briefing paper shares this information on how Bt operates: “When ingested by larva of the target insect, the Bt protein is activated in the gut’s alkaline condition and punctures the mid-gut leaving the insect unable to eat. The insect dies within a few days.”

It is for this reason why much research has been done to exploit the organism’s agronomic value. To date, there are more than 200 types of Bt proteins identified with varying degrees of toxicity to some insects.

In the past, Bt was cultured by fermentation. In fact, over the last 40 years, Bt has been used as an insecticide by farmers worldwide. It is said that organic farming has benefited from it as it is one of the very few insecticides permitted by organic standards. “The insecticide is applied either as a spray, or as ground applications. It comes in both granules and liquefied form.”

In a report, the Laguna-based International Service for the Acquisition of Agri-Biotech Applications (ISAAA) said that more than 18 million farmers in 27 countries planted biotech crops in 2013, reflecting a five million, or three percent, increase in global biotech crop hectarage.

“Accumulated hectarage of biotech crops planted worldwide to-date stands at 1.6 billion hectares or 150 percent of the total landmass of China,” said Clive James, author of the report and ISAAA Founder and Chairman Emeritus.

In Asia, Bt corn is now planted not only in the Philippines but also in China, Indonesia, Japan, Malaysia, South Korea, and Taiwan. It is also grown in the United States, Canada, Switzerland, and in some parts of South America and Africa.


But there are some issues against Bt crops. Critics claim that Bt proteins could target predatory and other beneficial or harmless insects and the targeted pest. The University of California reported that the Bt proteins had been used as organic sprays for insect control in France since 1938 and the USA since 1958 with no ill effects on the environment reported.

“The specificity of Bt for its target insects is one of the characteristics that make it an ideal method of biological pest control,” the briefing paper explained. “The specificity rests on the fact that the toxicity of the Bt protein is receptor-mediated. This means that for an insect to be affected by the Bt protein, it must have specific receptor sites in its gut where the proteins can bind. Fortunately, humans and majority of beneficial insects do not have these receptors.”

A 1999 study, which appeared in Nature, showed that in a lab environment, pollen from Bt corn-dusted onto milkweed could harm the monarch butterfly. Several groups later studied the phenomenon in both the field and the laboratory, resulting in a risk assessment that concluded that any risk posed by the corn to butterfly populations under real-world conditions was negligible, according to a study published in the Proceedings of Natural Academy Science.

A 2002 review of the scientific literature also concluded that “the commercial large-scale cultivation of current Bt–maize hybrids did not pose a significant risk to the monarch population” to quote a study entitled, “The case of the monarch butterfly: a verdict is returned,” which appeared in Trends Genet.

What about the effects among human beings? The US Environment Protection Agency has reportedly administered toxicology assessments. Bt proteins have already been tested even at relatively higher dosages.

According to the Extension Toxicology Network (Extonet), a pesticide information project of several universities in the US, “no complaints were made after 18 humans ate one gram of commercial Bt preparation daily for five days, on alternate days… Humans also ate one gram per day for three consecutive days and were not poisoned or infected.”

On tests conducted on dogs, guinea pigs, rats, fish, frogs, salamanders, and birds, the Bt protein was found not to have any harmful effects. Interestingly, the study found that no toxic effects were found on beneficial or predator insects, such as honeybees and lady beetles, Extonet reports.

The ISAAA claimed that Bt crops had benefitted food security, sustainability, and the environment. “Between 1996 and 2012, biotech crops have made positive contributions through decreased production costs and increased productivity (estimated at 377 million tons) valued at US $117 billion,” it reported.

Its environmental benefits included: eliminating the need for 497 million kilograms of pesticides; reducing carbon dioxide emissions by 27 billion kilograms in 2012 alone (equivalent to removing 12 million cars from the road for one year); and conserving biodiversity by saving 123 million hectares of land from being placed in agricultural production during the period 1996 to 2012.

“Bt crops are an addition to our arsenal against plant pests,” the briefing paper concludes. “With an increasing population and decreasing arable land, it is necessary to exploit all options with as little compromise to produce more crops. When used side by side with proper agricultural practices, Bt insect resistance technology can bring many benefits to crops, farmers, and consumers alike.”

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