Accurate identification is important to insect control and essential for application of insect pest management concepts. Scouting methods, equipment selection and application timing all depend upon correct pest identification. To aid in this process, two types of keys are presented in this volume: 1) a general key to adults of economically important insect families and related pests, and 2) field keys to the insect pests of each major crop based on the morphology and damage of the injurious life stages. In addition to the keys, illustrations of individual insects are also presented.
Crop advisors or managers will commonly encounter insects that have not been included in this volume. These will include insects of little or no economic significance and beneficial species. Variability in size, color and habits can also lead to confusion concerning the identity of a suspected pest. For these reasons, not all insects detected by fieldmen can be identified by using this book. In these cases, a specialist should be consulted.
Chemical Control. Although the use of pesticide application schedules is an integral part of the production of crops such as cotton, this type of control strategy is not feasible for most agronomic crops. Unlike high-unit-value crops such as cotton, fruits, or ornamentals, the economics of field crop production often does not justify the preventive use of expensive control chemicals. In these cases, cultural and other controls are of paramount importance in utilizing pesticides efficiently.
Nonchemical control tactics tend to be slow in action and primarily preventive in nature. Once an infestation is in full swing they usually are of little use. On the other hand, cultural practices, the use of resistant varieties, and other methods often prevent or substantially reduce the need for chemical control later in the season. When appropriate, these control measures are also discussed in the control section for each pest in the main body of the text.
Cultural Control. Practices such as the use of recommended planting dates, thorough weed control, and proper fertilization lead to the production of a healthy and vigorous crop better able to withstand insect injury. Early or late planting dates can be used with some crops and against some pests to avoid a pest's peak reproductive period. A combination of row spacing and planting date also has potential as a preventive control tactic for insects. Crop rotation, another cultural practice, has been used since prehistoric times as an efficient means of disrupting the development of most host-specific insects.
The insect-controlling properties of various tillage operations have long been realized. Such practices can be effective in one of several ways: 1) by directly destroying or disrupting soil-inhabiting insects, 2) by exposing such insects to unfavorable environmental elements, 3) by burying favorite weedy hosts or surface crop debris, or 4) by making an area unattractive to egg-laying adults. A notable exception to the above generalization concerns the lesser cornstalk borer. This caterpillar is primarily saprophytic under minimum or no-till conditions, but tends to be a crop pest in tilled fields. In most cases, however, tillage helps prevent damaging populations of soil-inhabiting insect pests.
Resistant crop varieties can also prevent economic insect injury in several ways. Some varieties avoid insect injury by lacking characteristics which particular insects prefer, e.g., smoothness or hairiness, a pleasing taste, a distinctive odor, a particular growth habit, etc. Another factor of resistance is the ability to tolerate insect feeding without accompanying yield reduction. Last of all, a resistant plant may possess some biochemical or morphological character which allows it to recover from incurred insect damage.
Natural and Biological Control. Although individual growers rarely have the opportunity or the resources to manipulate meteorological or biological factors for insect control purposes, understanding these factors can facilitate more informed control decisions. For this reason, the general effects of temperature, humidity, rainfall, and drought on the pest population are discussed in the insect notes along with general control practices. Likewise, major predators, parasites, and diseases of many pests are listed. In cases where parasite or disease relationships should be considered before initiating control practices, the telltale signs of such occurrences are explained. As a result, the extent to which these natural and/or biological factors are alleviating or promoting a pest situation can be taken into account when control decisions must be made.
Cooperative Control Efforts. Pest control strategies involving the manipulation of parasites and predators most often, but not always, involve the coordinated efforts of government officials and the growers in a particular area. The USDA Animal and Plant Health Inspection Service (APHIS) parasitoid release program for control of the cereal leaf beetle is one such project. Some cooperative control efforts, such as the boll weevil eradication program, do not involve biological control agents.
Pest Management. Thee tools of insect pest management are not new, but the strategy behind the movement is. The methods so far mentioned, in addition to various forms of chemical control, have been in use for at least several hundred years. The new pest management strategy, however, involves consideration and coordination of many of the above tactics to minimize the use of pesticides.
The pest management approach attempts to maintain pest populations below an economically damaging threshold by using a combination of available control tactics. Insect pest management systems usually rely heavily upon variety selection, planting date, optimum crop tolerance, promotion of beneficial organisms, scouting and other insect monitoring, thresholds utilization and judicial pesticide use. This manual may be of help in the area of scouting. In a pest management system, scouting consists of field sampling. Scouts must know the pests involved and recognize their damage. Thresholds cited for many pests in this manual have not been documented by exhaustive research. These thresholds are best estimates for taking control measures.