Development of Systemic Insecticides for Pests of Animals in the United States

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Abstract
Progress in the control of livestock insects by means of a systemic insecticide has been remark-able, when one considers that it has been only 19 years since Lindquist and his co-workers conducted the first successful laboratory test. During the following 14 years, most of the research was limited to studies in a few United States Department of Agriculture laboratories, but practical success with ronnel and Co-ral has greatly accelerated investigations. Most of the basic manufacturers of insecticides are now interested in developing chemicals for systemic control of livestock insects. Many state and Canadian workers have contributed to progress in this new field of research and development, and a considerable amount of research has been conducted in other countries. Presently recommended treatments do not consistently give 100% control of cattle grubs in practical applications, but do give an average of 80-90% control and therefore represent a great improvement over the rotenone sprays. Certainly, the present recommendations represent only a beginning. New chemicals are being investigated in an effort to find compounds with higher insecticidal efficiency and lower mammalian toxicity. It is hoped that in a few years there will be systemic treatments so effective against insects and so well tolerated by animals that the compounds can be mixed with salt or minerals for free-choice feeding to livestock. When this time comes, systemic control of livestock insects will not be limited to the control of pests which are not easily controlled by ordinary sprays. The labor-saving advantages of letting cattle treat themselves will displace many conventional spray treatments which are now considered quite satisfactory for the control of arthropods. Cattle grub control with systemic insecticides represents a major breakthrough. However, there are no really satisfactory recommendations as yet for the control of tabanids or mosquitoes attacking range cattle. None of the presently available treatments protect cattle more than a day or so from horse flies, deer flies, or mosquitoes. It may be that systemic insecticides mixed with salt or minerals, and constantly available in pastures, will solve this problem. At present, there is no way to protect deer and other wildlife from ticks and insects. These parasites not only kill these animals, but frequently pest populations build up on these unprotected hosts so that the arthropods cause damage to livestock. Many wild animals also act as reservoirs of livestock diseases transmitted by insects. Systemic insecticides administered to these animals may lead to the reduction of transmission of diseases from wildlife to domestic animals.