ABSTRACT
This chapter examines the causes of pest problems. It was clear from that analysis that a complex of factors causes pest outbreaks. Pest populations do not have to exist at such high levels to decrease crop yields. Estimates of expected pest losses for major crops grown without pesticides were made by examining data on current crop losses, loss data based on experimental field tests without treatment, and by consulting with pest control specialists. Diseases can also be prevented by planting only disease-free propagated material and by other cultural methods, which eliminate sources of inoculums through careful sanitation practices. Nonchemical controls in world pest control are even more important than in US pest control because smaller amounts of pesticides are used on the agricultural lands of the world. The dollar return per dollar invested in nonchemical controls has not been well investigated compared with pesticidal controls.
