Bt Cotton

Table 8 lists the 33 countries, in descending order of cotton hectarage that grew more than 100,000 hectares of cotton in 2001/02 and identifies the insect pests that can be economically important in the respective countries. The American bollworm, also called cotton bollworm (Helicoverpa armigera) is the most prevalent, found in 30 of the 33 countries, equivalent to a 90% incidence. It is followed by pink bollworm in 82% of the countries; other bollworms including Earias and Diparopsis spp.are found in 63 % of countries, armyworm (Spodoptera spp.) in 33% and tobacco budworm in 21% of countries. It is evident that American bollworm, pink bollworm and other bollworms such as the spiny bollworm in conjunction with Heliothis are of major significance and are known to cause very severe damage and crop losses globally. These lepidopteran arthropod pests feed on various crops and they migrate from one crop to another. High infestations of these insect pests can lead to very heavy losses and hence biological, cultural and chemical control with insecticides have been used to attempt control. For example, in Uzbekistan, the wasp Trichogramma is widely used as a biological control agent, but globally insecticide sprays remain the major control method. The data in Table 8 show that all 33 countries apply insecticide sprays, ranging from an average of 2 to 12 applications per annum. However, in many countries such as China and India, the maximum number of insecticide sprays in some regions of the countries where infestation is heavy, can be up to 30 insecticide sprays per season.

(To view Table 8, click here.)

The sequence of events leading to insecticide application is triggered when the infestation level exceeds the economic threshold. Broad spectrum insecticides not only decrease the population of natural enemies, but often result in the insect pest becoming resistant to the insecticide. This leads to more ineffective applications of the insecticide until eventually cost considerations lead to the abandonment of cotton cultivation, or a switch to alternative insecticides when this cycle, termed ‘pesticide syndrome’, is repeated (Doutt and Smith 1971, Benedict and Altman 2001). Insecticide-induced pest infestations, which in the past have caused catastrophic crop losses, have led to the general adoption of integrated pest management (IPM) which has had varying degrees of success on a global basis; insecticides, worth $1.7 billion on cotton globally in 2001, remain the principal method of control of insect cotton pests. The adoption of Bt cotton in the USA in 1996 and by China in 1997 represented a new concept of control and is an important element of IPM.

The data in Table 9 provides a global overview and summary of the relative levels of infestation (low, medium, medium to high, and high) of lepidopteran pests in the top 50 cotton-growing countries. The respective hectarage of cotton for each country is also listed in descending order. Nineteen of the 50 countries (38%) are in Category 1 where >70% of the national cotton area is infested by lepidopteran pests. Category 1 has 10 Asian countries, including those that grow a large hectarage of cotton, India, China, Pakistan and Australia, which account for 50% of the world cotton area of approximately 33.5 million hectares. Seven countries from the Americas are also included in Category 1 along with Egypt from the African continent and Spain from Europe. The total cotton area of the countries in Category 1 is 18.4 million hectares, equivalent to 55% of the 33.5 million hectares grown globally. Seven of the nine countries that have already commercialized Bt cotton are in Category 1; the only two exceptions are South Africa which is in Category 2 with medium to high infestation, and the USA in Category 3 with medium infestation. Field trials of Bt cotton have been conducted in an additional two countries in Category 1, Spain and Bolivia, bringing the total number of countries that have adopted or field-trialed Bt cotton to 9 out of 19 countries in Category 1, or almost 50%.

(To view Table 9, click here.)

In Category 2, the medium to high infestations, there are 21 African countries from all regions of the continent; they include countries from the west, east, central and southern Africa. The total area of cotton in the 21 African countries is 4.3 million hectares, equivalent to 13% of global cotton area. South Africa is the only country in this medium to high infestation category which has adopted Bt cotton. Field trials of Bt cotton have been conducted in Zimbabwe.

Category 3, with medium infestation, covering 31 to 70% of the national cotton area, contains only two countries, the USA and Brazil. The US adopted Bt cotton in 1996, and Brazil has conducted field trials of Bt cotton. The total area of cotton in these two countries with medium infestation is 6.3 million hectares, equivalent to 19% of the global area of cotton.

Category 4, with the lowest level of infestation (up to 30% of national cotton area infested with lepidopteran pests), has only eight countries out of the total of 50. These include the four Central Asian States of Uzbekistan et al, Turkey, Iran, Syria in West Asia, and Greece. None of the countries in this low infestation category have adopted Bt cotton but it has been field-trialed in Turkey and Greece. The total area of cotton in these eight countries with low infestation is 3.9 million hectares, equivalent to only 12% of the global cotton area.

In summary, 55% of the global cotton area is highly infested with lepidopteran pests (> 70% cotton area infected), 13% has medium to high infestations, 20% of the global area has a medium level of infestation (31 to 70% infestation), with only 12% of global cotton area in the low category with less than 30% of the national cotton area infested. Thus, 88% of the global cotton area, equivalent to 29 million hectares has lepidopteran infestations at medium to high levels, (31% to >70% area infested) where Bt cotton is likely to confer significant benefits over conventional cotton.

Related topics:

• The cotton crop
• Global distribution of cotton in developing and industrial countries, by area, production, consumption, imports, and exports
• Number of cotton farmers worldwide and size of farms
• Crop losses due to insect pests of cotton and the cost of control
• Global insecticide usage on cotton
• The use of Bt genes in cotton
• Assessment of environmental risk and Insect Resistance Management (IRM) strategies
• Global adoption of Bt cotton
• Bt cotton experience to date
• Summary: Agronomic, Environmental, Social and Economic Benefits
• Future global potential for Bt cotton: opportunities and challenges
• Highlights

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