Insect control strategies

The analysis of neuropeptides in insects may lead to the development of both specific insect control strategies and model systems that clarify the role of neuropeptides in all animals. Therefore it is important to vigorously pursue neuropeptide studies and to exploit the available technologies to the fullest. This paper will review the importance of current recombinant DNA techniques to the study of neuropeptide biology. Studies of the adipokinetic hormone (AKH) family will be emphasized as examples, but other peptides will be mentioned to present a broader picture of the advantages and problems associated with the techniques. 

Tony Hooper (Rothamsted Research, UK) discussed local applications of push-pull insect-control strategies with plant-derived semiochemicals and pheromones in the control of crop pests. For example a sudan grass trap crop reduced the number of stem borers on maize grown in adjacent plots. Five thousand African farmers have already been involved in a practical test of the methodology which exploits plant diversity in a very creative way. It was an excellent example of an understanding of chemistry and biotechnology being put to practical use in a local context. 

The development of transformation systems will yield major breakthroughs in establishing advanced insect control strategies. 

Reproductive Behavior. Male accessory glands contain peptides which affect female reproductive behavior. Female sexual receptivity is diminished after mating (22) and oviposition is stimulated (22). Peptides responsible for these behaviors have been isolated from Drosophila species (22,23) and sequenced. In addition, a peptide with similar behavioral influences in a lepidopteran has been isolated from Helicoverpa zea (24). Miller (this volume) discusses the potential of these "sex peptides" in the development of unique insect control strategies. While males influence female reproductive behavior via the action of "sex peptides", females, especially in the Lepidop-tera, influence male behavior through the release of pheromone. The production of pheromone, in turn, is controlled by the pheromone biosynthesis activating neuropeptide (PBAN for a comprehensive review see 25). PBAN-like activity has been observed in more than 20 insect species (25) and offers another avenue for exploitation of neuropeptides in insect control. 

Prior to the interest shown in baculoviruses as protein expression vectors, augmentation of natural populations of these insect-specific viruses had been in use for decades, as an insect control strategy (32). Due to the nature of baculovirus infection of lepidopteran larvae, it takes several rounds of viral replication within the larva before the larva succumbs to the infection. This may take firom days to weeks according to environmental conditions. Baculoviruses are used therefore mainly against pests of crops which can sustain some degree of damage, without significant economic loss (32). 

Strategy Problem 7 Synthesis of a single enantiomer. Many compounds such as pharmaceuticals, flavourings, and insect control chemicals must not only have the right relative stereochemistry but must be optically active too if tliey are to be of any use. Consider the strategy of synthesising one enantiomer ... 

Sex pheromones have found a place in monitoring for the presence of insects as a guide to when spraying of conventional chemicals might be needed. However, the use of pheromones to attract insects and then trap them is not an effective control strategy because males only are attracted and the trapping has to be close to 100% effective to reduce mating in the field and this, to date, has been unachievable. The use of lure and kill ... 

The chemical and behavioral aspects of the sex pheromones of several forest defoliating insects of economic importance in eastern Canada are presented, with emphasis on the spruce budworm, Choristoneura fumiferana. Studies conducted over several years in New Brunswick on the use of pheromones as potential control agents, using in particular the air permeation technique to effect mating disruption, are discussed. The identification and the behavioral effects of minor components of the spruce budworm pheromone system are presented and the potential exploitation of their behavioral roles in the mating sequence in terms of control strategies are addressed. 

Renou M. and Guerrero A. (2000) Insect parapheromones in olfaction research and semiochemical-based pest control strategies. Annu. Rev. Entomol. 45, 605-630. 

Our strategy for an endocrinologic approach to insect control therefore was based upon the search for anti-juvenile hormones. 

As previously stated, these compounds do not show antijuvenile hormone activity against all insects, but open the door to a new mode of insect control which affects most insect stages and provides a broader dimension to the endocrinologic strategy of insect control. 

Mannal controls are simple and inexpensive pest-control strategies, since the only tools required are your time and patience. Besides controlling pests, manual controls require that you closely examine plants, increasing the likelihood that you ll detect the early symptoms of insect or disease problems. 

Use the pest-control strategies in this section to lure pests into situations from which they can t escape. Pest baits and lures can be visual (using color or light to attract the pest), sexual (using pest-specific pheromones), or dietary (using preferred insect foods or kairomes, which are feeding stimulants). 

Research in molecular genetics of insect neurohormones, specifically neuropeptides, will facilitate rapid advances especially in identifying the pheromones and cloning neuropeptide genes into microbes for production purposes and into plants for novel control strategies. 

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