Supervised Control of Insects utilizes parasites and predators and makes chemical control more efficient

Supervised control of field crop insect pests was first developed on the northwest side of the San Joaquin Valley. For three years it has been in successful operation in connection with the control of the alfalfa caterpillar, and has been expanded to the control of other pests on alfalfa and to pests of cotton. Supervised control has not been developed for such crops as deciduous and citrus fruits or truck crops. It has its possibilities on other crops but the necessary entomological information either has not been developed or has not been tested for a local supervised control district. A successful supervised control program in a district requires the following: an intimate knowledge of the insects; a sufficient acreage to finance the district; an informal grower coijperative to administer the district and a properly trained entomologist to supervise the insect control. Each of the California supervised control districts is managed by a group of growers cooperatively employing a graduate entomologist for the summer. This entomologist is responsible to the growers only. Supervised control is based on studies of the interrelationship between the pests and their environment-ecological studies-conducted by members of the Division of Entomology and Parasitology. From these studies it is now possible to predict outbreaks of the alfalfa caterpillar three days to two weeks ahead of injury. These predictions make it possible to utilize cultural controls to their fullest extent and to time any necessary chemical control most effectively. The methods of supervised control are essentially systematic surveys of the fields in an area with the objective of locating all potentially destructive pest populations before they have had an opportunity to do any damage. The standard by which economic infestations of the alfalfa caterpillar are judged is a sliding scale centered around 200 large or potentially large larvae per 20 sweeps of the standard net. This center point-of 200-is used for average conditions which rarely exist. Other factors such as growth, stand, time remaining until harvest, oviposition rates and weather must be taken into consideration. For example, this center point is too low for dense, vigorously growing alfalfa and for infestations developing during cool weather. Insect infestations frequently develop so insidiously that the average grower does not see the evidence of the insects until considerable damage has occurred. Not all fields require treatment. For example, in outbreaks of the alfalfa caterpillar it is seldom that as much as 50% of the fields require treatment even in heavily infested areas. In such cases, it usually is not more than about 20%. When the actual populations are not followed, many fields are treated unnecessarily. Under a supervised control program, it is not necessary to treat as an insurance against the possible development of economic infestations. The unnecessary use of insecticides is a needless expense and may be harmful to beneficial insects.