Insect infestations and their effects on the growth and yield of field crops: a review

Abstract

AbstractA knowledge of the often complex relationship between insect populations and their effects on the yield-forming processes of crops is useful for assessing pest status and for devising methods of minimising the effects of infestation on yield. After a preliminary section on definition of terms, consideration is given to ways in which insects injure plants and crops, particularly annual crops. Investigations into the yield-forming processes of unattacked crops can often provide useful insights into the likely effect of insect injuries on yield. The differences between the characteristics of individuals and populations are discussed, both of insects attacking plants, and plants responding to the attacks of insects. The distribution of insects on plants and on crops and the effect that this has on damage is considered, as is the time and duration of the attack in relation to the growth cycle of the crop. The components of plant resistance to insect attack are then discussed, especially tolerance and the various ways in which plants and crops compensate for injury. The review concludes with an examination of the quantitative relationships between numbers of insects or injuries and their effects on yield. The generalised response is a sigmoid curve relating an upper and lower plateau of yield where changes in the numbers of insects or injuries have little effect. Most relationships conform to some part of this curve, though few show all its features.