Conventional Chemical Insecticides Research Articles

Increased insecticidal effect by a recombinant baculovirus carrying a synthetic diuretic hormone gene

Genetically engineered insect viruses may be potential alternatives to conventional chemical insecticides. A recombinant gene for the diuretic hormone of the tobacco hornworm, Manduca sexta, has been introduced into a baculovirus, Bombyx mori nuclear polyhedrosis virus (BmNPV). When silkworm larvae were injected with the resulting recombinant BmNPV, the diuretic hormone was expressed, causing a strong alteration in larval fluid metabolism. The recombinant virus killed infected larvae about 20% faster than the original virus.

SUSCEPTIBILITY OF FIVE SPECIES OF SASKATCHEWAN GRASSHOPPERS TO FIELD APPLICATIONS OF NOSEMA LOCUSTAE (MICROSPORIDA)

The potential usefulness of Nosema locustae Canning as a microbial agent for grasshopper control was first demonstrated by Henry (1971) and Henry et al. (1973). These authors found that a 50–60% reduction in grasshopper density (as compared with untreated populations) could be achieved, and they speculated that 35–50% of the survivors would be sufficiently infected so that their fecundity would be reduced. The value of incorporating such an agent into a grasshopper pest-management system is obvious: By suppressing high insect densities to manageable levels, the need for conventional chemical insecticides could be reduced and perhaps even restricted only to “hot spot” areas. The objectives of the study we report here were to: (1) Determine if N. locustae was infective to the predominant species of grasshoppers in Saskatchewan; (2) if so, monitor the development of the disease within the populations; and (3) determine if the pathogen could survive over the winter and infect next year's populations. Because this was a preliminary experiment, we did not attempt to determine any effect the pathogen might have on population reduction.

The Potential of Autocides and Microorganisms as Ecologically Acceptable Agents for the Regulation of Spruce Budworm Infestations

AbstractThe spruce budworm (Choristoneura fumiferana) is the most economically important indigenous pest in eastern North America. In order to protect valuable timber the budworm population must be restricted to endemic levels. To achieve this, and simultaneously attempt to improve environmental quality is a major objective of much research into the development of new insect control methods.This review presents an encapsulated report of researches into the use of pheromones and hormones (autocides), and viruses, fungi, bacteria and microsporida (microorganisms) as possible control agents. Such agents would be more selective than conventional insecticides. Several of the control methods discussed in this report are almost operational, and while it is evident that none of them can completely replace chemical insecticides, field tests indicate that they have a potential in budworm control. The results also indicate the urgent need for testing the integrated use of the autocides and microorganisms, and the integrated application of these newer control agents with conventional chemical insecticides.

The Role of Chemicals in the General Insect Control Picture

When reference is made to chemical control of insects, we tend to think only of conventional insecticides. However, even with the alternate methods of controlling insects now used or being investigated, chemicals are likely to be involved in one way or another. For example, scientists engaged in research into the nature and cause of the resistance in plants to insects are finding that in some instances, at least, chemical substances deter insect attack or retard insect development (Beck and Stauffer 1957, Klun et al. 1967) ; thus research in this field may eventually provide valuable clues for the development of new types of insecticides. Even control of insects with pathogens may prove to be the result in part of the action of a chemical substance since Bacillus thuringiensis Berliner the only insect pathogen registered for use on crops, contains a chemical component that produces insecticidal action (Heimpel 1967). In addition, chemicals are involved in the sex attraction of many insects (Butenandt and Hecker 1961, Roller et at. 1966, Sekul and Cox 1965, Jones et al. 1966, Berger 1966, Jacobson 1965). Definite chemical substances are responsible for the attraction or the feeding responses of insects to certain host plants, and synthetic chemical lures are proving useful for the detection and control of a number of insects. Also, the interesting and important findings on insect hormones, a field receiving more and more attention in research programs, have to do with the discovery of the chemicals that regulate the development and behavior of insects. And, finally, the use of sterilization to control insects may require chemicals that produce sterility in the natural population or sterilize insects for release. Thus, though conventional chemical insecticides now play the most prominent role in the control of insects, other types of chemical agents will also probably be used in some of the most promising alternative methods of control.