Questions an optimum planting time, whether the crop is developing and fruiting on time, and when to initiate pest control actions are particularly difficult to answer, because the timing is not always the same each year. Growth and development of crop plants may vary as much as two to three weeks from the "normal". Many factors, such as length of the growing season, climate (including solar radiation, temperature, light, wind, rainfall, dew), variety, availability of nutrients and soil moisture, pests, arid cultural oractices affect cotton growth (1, 2). Under normal growing conditions, growth and development of the cotton plant follows an orderly and predictable pattern. This pattern can be projected by using mathematical models. Models have been developed for the cotton crop and for several of its major insect pests. Generally, these models are primarily based on degree-days (i.e. accumulated heat units).

Although computer technology has become a part of our daily life, its utilization in agriculture, especially in crop management is still minimal. During the past 15 to 20 years researchers and growers have been exposed to the concepts of modeling, systems analysis, and general computerization of research findings. Nevertheless, despite this inundation, very little practical application of such theory has reached the growers. The correlation of such cotton plant and insect models in the decision-making process has been difficult to implement in the field. This need for a practical means of utilizing complex models led to the development of the Cotton Slide Rule (8). The Slide Rule is intended to bridge that gap between the laboratory and the field, and make mathematical models useful to and useable by growers in cotton management.