MODELING PRODUCTION AND PROTECTION OF COTTON CROP IN MIDDLE EGYPT

A physiologically based model has been developed for use in addressing crop and pest management decisions in processing cotton (COTTAMIN Model). Field studies were conducted during the 2004-2006 cotton growing season in Fayum Governorate, to detect the adult population of the pink bollworm, Pectinophora gossypiella, cotton leaf worm, Spodoptera littoralis, cotton aphid, Aphis gossypii, sweetpotato whitefly, Bemisia tabaci and twospotted spider mite, Tetranychus urticae. Field generation numbers, life table parameters for the field, thermal requirements and heat unit accumulation were used. Cotton plant phenology was recorded as well as weather factors. The relationships in cotton complex were detected. The interaction of pest (5 pests), plant (phenology) and weather (four factors) were tested in COTTAMIN Model on two cotton varieties (Giza83 and Giza 90). A comparison was made between the expected and observed data. Most of the validations produced results that were in reasonable agreement with the observed data. The forecasts were more accurate when the phenology of the population peaks was compared than when actual population densities were compared. In general, no computer model can make perfect forecasts; however, we can use COTTAMIN Model successfully to help make pest management decisions in cotton fields. Introduction Modeling techniques applied to agriculture can be useful to define research priorities and understanding the basic interactions of the plant-climatic system. Using a model to estimate the importance and the effect of certain parameters, a researcher can notice which factors can be most useful. Beginning in the mid-1960 through the present, a considerable effort has been directed at development of computer models of agricultural systems. These physiologically based strategic type models have proven particularly useful for defining what we do not know about a system, in the process providing a degree of focus not normally obtained in other research programs. More recently, systems biologists have focused on the development of tactical crop and pest management models, in some cases reemphasizing the physiological aspects and choosing a more empirical approach to addressing this problem. In Egypt, cotton is subjected to yield and quality losses by insect pests. The pink bollworm (PBW), Pectinophora gossypiella and cotton leafworm, (CLW), Spodoptera littoralis are the most destructive pests causing significant losses to yield. Larval feeding within bolls is the basis for most economic losses caused by these pests. Since the larvae penetrate the bolls soon after hatching, efficient control by insecticides is hard to achieve. In addition, application of toxic insecticides may result in increased pest resistance to insecticides, interference with the activity of beneficial insects, environmental pollution, and hazards to public health. The reduction of insecticide applications in cotton is, therefore, of great benefit. Cotton bollworm has a number of difficult problems regarding sampling techniques, i. e. a)larvae feeding inside green bolls causes special difficulty in estimating their population density; b)PBW and CLW are multi-generational. Amin et al. (1994) found that PBW had four generations and CLW was found to have seven overlapping generations (Bishara 1926, Abdel-Badie 1977, Dahi 1997). The indiscriminate use of insecticides has caused a number of problems to various ecological niches around the world including Egypt. Hence there is a growing necessity and interest in the use of ecological approaches for management of these pests. The rates of development in insects under natural conditions are largely driven by temperature. In most microenvironments, temperature is characterized by daily and seasonal cyclic variations with superimposed irregular fluctuations. However, studies of insect development rate most often involve experiments performed under constant 104