Insect pests are recognized to cause significant crop losses and to be a major constraint to cotton productivity throughout the world. In the absence of any control measures (resistant varieties, insecticides, cultural control, IPM), potential losses due to cotton insect pests on a global basis would be in the range of 35 to 41% (Oerke 2002). The actual losses that currently occur, despite control measures in place, are estimated to range from 7 % to 24 % (Table 10). Crop losses are correlated to the level of infestation, which will vary by year, by country, by crop variety. The data in Table 10 show the range of actual and potential crop losses for different global regions. These data are general global estimates, and are useful in exhibiting differences in order of magnitude and patterns of loss for different regions.

The data indicate that average potential crop losses globally due to cotton insect pests, in the absence of any control measures, would be of the order of 37 % with no significant differences between global regions; this compares with an average actual loss of about 21 to 22%, suggesting current controls save about 15% of yield. Whereas there are no significant differences between regions for potential losses, there is a substantial difference between continents and regions in terms of actual losses. The highest actual losses occur in Africa in the range of 20%, followed by Asia at about 13 %, the Americas at 11%, and the CIS, Europe and Oceania at 11%, 9% and 7% respectively. The general pattern of actual losses indicates that in the more tropical developing countries, losses are generally higher than in the more temperate regions of developing and industrial countries.

The estimate of actual losses due to cotton insects by Oerke (2002) for North America, which includes the USA and Mexico, is 11%. Detailed estimates of losses due to insect cotton pests in the US have been compiled since 1979 by cotton entomologists for the US cotton belt (Williams 2002a, 2002b, 2001, 2000, 1999, 1998, 1997, 1996 www.mmstate.edu/Entomology/Cotton). The average loss reported for the 18 year period 1979 to 1996 was 7.5% (Williams 1997b), with the bollworm/budworm complex reported to be the most important pest in 13 out of the 18 years. For the period 1994 to 2001, cotton insect losses in the US have ranged from 4.5% to 11.1% (Table 11) with the value of loss/hectare ranging from $ 65/hectare to $ 145/hectare with an average of approximately $ 100 per hectare; this translates to an annual loss of approximately $ 500 million at the national level in the US.

In addition to the $ value of crop loss, the US data in Table 11 check also includes the cost of control, the major portion of which is insecticides and their application. During the period 1994 to 2001 control cost ranged from $113/hectare to $158/hectare. Taking into account both crop loss and the cost of control, which is the total cost to US farmers associated with cotton insect pests, this ranged from $187/hectare to $293/hectare which is substantial; these translate to national annual losses in the US due to insect pests of $1.0 billion to $1.7 billion.

Taking into account that a large proportion of cotton is grown in the more tropical developing countries where insect infestations and crop losses are higher, and more insecticide sprays are applied, the total cost associated with cotton insects is substantial. Acknowledging that there is no uniform database and methodology available for calculating precise values of crop losses and control costs associated with cotton insects globally, various data are used to derive estimates that provide indications of the orders of magnitude involved. The US data base (Williams 1997b, 2002a) is by far the most rigorous and detailed, with a long term average for crop loss of 7.5% plus control costs for an average value of approximately $1.4 billion annually. Oerke’s estimates of loss for the global regions range from 7 to 24% with an average of about 15%.

With a gross loss in the range of 15% globally, the value of crop losses due to cotton insect pests, based on a $20 billion production in 2000/01 is $3.0 billion plus $1.7 billion for insecticide for a total cost of approximately $5 billion. This estimate is conservative given that: it does not include insecticide application costs; that the average annual cost in the US alone is $1.4 billion over the period 1994 to 2001; and that China estimates the annual losses to bollworm alone at $1.2 billion (Jia 1998) and India $300 million (King 1994). It is evident from these latter references and others that the bollworm complex is the major component of crop loss associated with cotton insects in both developing and industrial countries. The bollworm cotton complex probably costs cotton farmers worldwide approximately $3 billion annually; this covers yield loss and control costs, excluding labor for sprays. Published experimental data on the increases in production from Bt cotton, when compared with conventional cotton, provide confirmatory evidence that yield increases of 10% or more are representative for the US (Kerby 1996, Benedict and Altman 2001) and up to 30%, or more, in major cotton-growing countries such as India (Naik 2001), which suffer heavy infestations of the bollworm complex. Thus, excluding the substantial labor costs involved in applying many insecticide applications to 33.5 million hectares of cotton, insect pests cost at least $5 billion annually, with bollworms being the principal pest.