WASTES IN RELATION TO AGRICULTURE AND FORESTRY 



79 



and domestic animals can become exposed to the 

 insecticides used. 



Basic research on degradability, fate, and me- 

 tabolism of the newer insecticides is accelerating 

 the solution of the residue problems brought about 

 through the use of persistent insecticides. In spite 

 of the progress made, there is still extensive use of 

 the persistent insecticides in agriculture for con- 

 trolling insects on nonfood crops, soil insects, and 

 medically important insects. 



Alternate Methods of Pest Control. — Although 

 use of conventional chemical insecticides for insect 

 control has received much research attention in the 

 past, most of the current research on insects in the 

 U.S. Department of Agriculture and the State 

 agricultural experiment stations is oriented to the 

 development of ways to control insects by various 

 biological or physical means, or by developing 

 highly selective chemicals such as insect attract- 

 ants to which only the target insect will respond. 

 Thus, it is hoped to eventually achieve control of 

 most of the important insect problems without 

 creating the adverse effect on other organisms that 

 is so characteristic of broad spectrum chemical 

 insecticides. 



The chief biological methods for the control of 

 insect pests are by the use of other insects (para- 

 sites and predators) or microbial pathogens. 

 Foreign exploration for insect parasites and pred- 

 ators in the native home of pests accidentally in- 

 troduced into the United States constitutes one of 

 the important lines of research that has been em- 

 phasized for more than 70 years. 



The first successful introduction of a foreign 

 predator to control an insect involved the intro- 

 duction of the vedalia beetle in 1889 to control the 

 cottony cushion scale on citrus. 



The gypsy moth was accidentally introduced 

 into Massachusetts in 1869. Without natural ene- 

 mies, it became a ravaging pest of forest, orna- 

 mental, and fruit trees. In 1905, the State of Mas- 

 sachusetts and the Federal Government began to 

 introduce natural enemies of the gypsy moth. The 

 control of this insect by predators was not at first 

 highly successful. Alternative hosts for the preda- 

 tors were not present in this country. However, 

 continued research on gypsy moth parasites has 

 developed a situation in which the gypsy moth is 

 now a relatively manageable pest in most States 

 even though major control programs are occasion- 

 ally needed. 



The success of early efforts to control insect 

 pests by introducing beneficial insects has led to 

 the introduction of a wide range of parasites and 

 predators. The results of this research approach 

 have ranged from highly successful to complete 

 failure. 



Imported parasites and predators for control of 

 balsam woody aphid and larch casebearer have ex- 

 erted control in some areas. Control of these two 

 pests is especially encouraging. 



The continuing worldwide search for beneficial 

 insects has produced parasites of such recently in- 

 troduced pests as the cereal leaf beetle and the im- 

 ported fire ant. 



In the past, most research on biological control 

 agents was allocated to the collection and release 

 of biological agents with the expectation that such 

 agents would survive and multiply on their own, 

 and thereby play a vital role in control of the tar- 

 get pest. In recent years, more effort has been allo- 

 cated to the mass production and sustained release 

 of biological agents for direct control of the pest. 



InsecCs are subject to infection by a wide range 

 of disease organisms, including bacteria, viruses, 

 fungi, and protozoa. Most of the research on bio- 

 logical control of pests has involved microbial 

 agents. Several hundred kinds of insect pathogens 

 have been found to cause diseases in insects. Re- 

 search with laboratory animals and human volun- 

 teers has indicated that certain insect viruses are 

 not harmful to warmblooded animals, and goner- 

 ally do not even adversely affect closely related 

 insects. 



Research on (he nutritional requirements of in- 

 sect pests has contributed to a capability to arti- 

 ficially produce pests en masse. This, in turn, en- 

 ables production of parasites, predators, and 

 pathogens in enormous numbers as needed. : 

 example, cooperative research between the \ 

 Department of Agriculture and Canadian insect 

 pathologists has enabled the production of a v 

 disease of the European pine sawfly. The control 

 of the Douglas fir tussock moth with polyhedn - - 

 virus has been brought to the pilot-plant stage. 



Insect attractants have been recognized since the 

 thirties, when considerable work was done on at- 

 tractants Eor bark beetles. Only in recent years 

 a widespread interest developed in exploring this 

 profitable area o( research. Lnsect attractants • 

 duced by plants I food or ovipositional lures), by 

 insects themselves (sex lures), or synthetic 



