Surveys of Insect Pests

G. J. Haeussler, R. W. Leiby.

Surveys are an intelligence service that provides the entomologist, plant quarantine official, farmer, county agent, and the insecticide industry with essential information regarding the insect enemy. The surveys tell where the enemy occurs, how abundant he is, and what damage he is causing or threatens to do. They are a basis for determining the need and type of action required to combat him.

The many kinds of insect surveys vary according to the objective and the circumstances of the particular problem. Some provide information about a species about which little is known, such as a pest new to an area or the country. Some concern the kinds of insects that attack a given crop, like cotton, or a group of crops, like vegetables or fruits, and are for the purpose of aiding farmers to protect such crops from loss due to insects. Others aid in planning organized control campaigns against specific pests, like grasshoppers, which periodically occur in outbreaks over large areas and require cooperative action by several agencies and organized groups. Some surveys are conducted primarily to obtain data as a basis for determining the need for and as a guide to the enactment of State or Federal quarantine or regulatory measures. Still other surveys are made primarily to provide a record of the occurrence, abundance, and host-plant relationships of all insect species within a given area, such as an entire State. In wartime, surveys are carried on as a defense measure in the event that deliberate attempts should be made to introduce injurious pests from abroad or to spread those of economic importance to new areas.

SURVEYS for a recently introduced or little-known pest are conducted primarily to determine its distribution and behavior, to determine the nature and extent of damage it causes, the manner and rate by which it spreads and to ascertain its potential destructiveness and the need for developing control measures before it can become widely distributed.

An example is the work by the Bureau of Entomology and Plant Quarantine and State agencies in the South to obtain information on the distribution and status of the imported fire ant. This little South American pest, first reported near Mobile, Ala., about 1918, has spread and increased to the extent that citizens in infested areas demanded action to control it. The surveys, started in 1949, have shown the pest to be widely distributed in Alabama and Mississippi and less abundant in Florida, Georgia, Arkansas, Tennessee, and Louisiana. The observations also suggest that shipments of nursery stock may be a common means by which the ant is spread.

SURVEYS OF THE INSECTS attacking a given crop or group of crops have been carried on extensively. During the Second World War supplies of the insecticides for the insect pests of essential crops were scarce, and nearly all the basic materials needed to make insecticides were placed under allocation control. Supplies therefore had to be conserved and the available stocks used only for the most pressing needs on crops having the highest priorities. As a part of the effort to make the best use of insecticides and equipment, the Department of Agriculture in cooperation with other Federal and State agencies and industry instituted special surveys of the insect pests of cotton, truck crops, and fruit and their control requirements.

Whenever possible, a special effort was made to anticipate the development of infestations. Information obtained from the surveys was circulated weekly or oftener to all persons and agencies that needed to plan programs and advise farmers about protecting the crops. It indicated the localities where dangerous numbers of insects were attacking or likely to attack specific crops, the local or regional availability of the necessary insecticides, and the availability of equipment. Extension workers advised farmers promptly as to the situation in local areas by announcements over the radio, in newspapers, and through correspondence. Information from the survey was used by Federal officials to aid industry in obtaining supplies of the basic materials needed to produce additional quantities of insecticides or equipment and guided industry in the distribution of the limited supplies to meet emergency situations.

The emergency situation with respect to availability of insecticides and equipment remained an important problem to the producers of cotton, vegetables, fruits, and other essential agricultural crops, and it has been necessary to continue surveys of this type. For instance, entomologists in New York knew that the Mexican bean beetle entered hibernation in the fall of 1949 in larger numbers than ever. They also knew that because of the mild winter an unusually high percentage of the beetles would probably survive to infest the State's dry bean crop, worth 13 million dollars, in 1950. State workers made surveys in June 1950 to determine whether beetles were present on beans in numbers sufficient to threaten the crop. Counts of the beetles made in 15 counties showed that the insects had survived the winter in such numbers as to necessitate the application of control measures to prevent extensive losses. An intensive control campaign was developed immediately. An evaluation of the results of the control measures instituted because of the survey findings indicated that the growers of dry beans of New York profited by $3,04,094 from an expenditure of $785,162 for insecticides and the labor to apply them.

Several States now conduct surveys of the insect pests of vegetables, fruits, the cereal and forage crops, and cotton and make the results available promptly in periodic reports. County agents, other agricultural advisors, and farmers thus are informed as to the status of insect conditions in their areas. The Bureau of Entomology and Plant Quarantine, through its field offices, assembles the survey data from the various States and summarizes and distributes it in weekly reports that show insect conditions throughout the country with regard to those crops.

The surveys of cotton insects have resulted in a great expansion in the use of control methods. The number of growers applying controls throughout the Cotton Belt has increased more than 100 percent since 1945 as a result of the advisory program made possible because of the survey. The survey of cotton insects has developed into an advisory service for farmers, others associated with cotton production, and the manufacturers of the insecticidal chemicals.

An advisory type of survey, much like those we have mentioned, provides advice to farmers on the timing of insecticide applications. An example is the surveys of the European corn borer, first conducted in 1948 by the State agricultural experiment stations of Illinois, Iowa, Minnesota, and Wisconsin and the Department of Agriculture and later expanded to include I other States. Research has shown that the losses caused by the insect can be reduced by the proper use of insecticides, but accurate knowledge of the development of the corn borer eggs and larvae is essential because the period for effective control is short and the timing of insecticide applications is critically exacting. Farmers cannot now determine this development accurately. On the basis of field information obtained by trained personnel, advice is given to farmers every week or oftener by State extension workers over the radio and in newspapers to guide them in carrying out control measures in areas where corn is threatened. A cooperative survey of this type, carried on in 12 States in 1949, helped save some 10 million bushels of corn from loss by the borer. It also helps farmers to avoid unwise use of insecticides and the cost of unnecessary applications by advising them that the degree of infestation in their locality does not warrant treatment or that the time for effective control has passed.

SURVEYS OF PESTS that occur in periodic outbreaks form the basis for planning regional or national cooperative or volunteer control programs. Grasshoppers and Mormon crickets, chinch bugs, hessian flies, and screw-worms are such pests. The surveys vary according to the particular problem, but all are conducted cooperatively by Federal and State agencies. The annual grasshopper survey, for example, is carried on to provide in advance a general picture of the infestation to be expected as a basis for planning control needs for the following season. The knowledge obtained by surveying the population of grasshopper adults and later the eggs is mapped during the winter and enables control agencies to plan their needs for the coming year. The actual grasshopper population is then determined by surveys in the spring after natural enemies and weather have exerted their influence. Further scouting, following the application of control measures, provides information concerning the thoroughness of control coverage, effectiveness of results, and the need for changes in insecticide dosages, application methods, or other procedures.

SURVEYS CARRIED ON in relation to regulatory measures are among. the most common types. They furnish a basis for the enactment of State or Federal quarantines against specific pests. Most such surveys are designed to delimit the areas of infestation and may involve inspection of plants, plant products, soil, or other commodities to determine ways by which the particular pest is spread. Examples are the surveys of gypsy and brown-tail moths, the Japanese beetle, white-fringed beetles, the sweetpotato weevil, and the potato tuberworm. Such surveys are usually conducted by the Federal and State units. Special methods and equipment such as traps and lures are often used in the surveys. For instance, traps baited with a material that attracts adult Japanese beetles are placed each summer near airports and other strategic points outside the regulated area to detect new infestations that may get a start from the escape of hitchhiking beetles. For the survey to determine distribution and spread of the pink bollworm, gin-trash machines have been developed; they separate any pink bollworms that may be present in the trash that is regularly removed from seed cotton during the ginning process. Examination of samples thus collected provides a relatively simple and reliable means of detecting the presence of the insect.

A SPECIAL SURVEY for insect pests and plant diseases in the general vicinity of ports of entry was carried on by the Bureau of Entomology and Plant Quarantine in 1943-45. The project, a national defense measure, was undertaken because of the belief that the greatly increased traffic from overseas during the Second World War might have resulted in the entry and establishment of new foreign agricultural pests in the port areas. It entailed intensive inspection of cultivated plants, field crops, orchards, home gardens, ornamentals, and native plants. Special attention was paid wild plants belonging to families closely related to important cultivated crops. The search was concentrated in States along the eastern and west coasts, Gulf coast, and Mexican border. The major effort was in southern California, the Rio Grande Valley, and in States bordering the Gulf of Mexico, where survey crews worked the year around.