Insect growth and development

Figure 7. Kauranes that inhibit insect growth and development.

Most previous experiments with kauranes and closely related compounds have been concerned with their effects on Insect growth and development. However in this case the deterrent effects of the Isolated compounds to Trirhabda canadensis were investigated as a first step in understanding the feeding behavior of this insect in the field. 

Role of Mixed-Function Oxidases in Insect Growth and Development... 

In addition to their well established role in catalyzing the metabolism of a wide variety of naturally occurring and synthetic xenobiotics, cytochrome P-450-mediated mixed-function oxidases are of critical Importance in the biosynthesis and regulation of the major hormones (ecdysteroids and juvenile hormone) that control insect growth and development. The characteristics of the mixed-function oxidases involved in the synthesis of insect hormones are described and the possibility that the enzymes might represent potential targets for insect control is discussed. 

The stilbenes from the bark of Yucca periculosa F. Baker had growth regulatory activity against the Fall Army worm, an insect pest of com. 3,3, 5,5 -Tetrahydroxy-4-methoxystilbene was found to be the most active compound showing significant effect at 3 pg/g in diets. The results indicate the possible correlation of some antioxidant activities with insect growth and development [498],... 

Many secondary metabolites found in plants deter phytophagous invertebrates, sometimes even modifying insect growth and development if included in the diet [8]. Natural products can often act as insecticides via different pathways, as is the case with the analogues of insect juvenile hormones produced by plants. Thus, some derivatives of these analogues are used as commercial insecticides while others act as ecdysteroid antagonists [8]. 

Dhadialla, T.S., Retnakaran, A., Smagghe, G., 1998, Insect growth-and development-disrupting insecticides in Comprehensive Insect Molecular Science, Vol. 6, Gilbert, L.l., latrou, K., Gill, S.S. (Eds) Elsevier Pergamon, New York, 55-100. 

Although there is evidence that phytoecdysteroids do affect insect growth and development upon ingestion, this role should be evaluated in the context of multifaceted chemically based resistance in plants (Camps, 1991). 

In order to understand fully the importance of these chemical factors, it is necessary to consider the processes which are probably responsible for their diversification. A mechanism of coevolution of insects and plants was set forth eloquently by Erlich and Raven (4). According to their hypothesis, angiosperms produced a series of chemical compounds which were not directly related to their basic (or primary) metabolic pathways, but which were otherwise not harmful to the plants growth and development. 

A cadaver exposed to the environment is subject to degradation by various types of animals, of which insects are often the most predominant. Insects can affect the breakdown of the corpse by augmenting the internal decomposition process (Campobasso, Di Vella, and Introna 2001). The succession and development of some insects that visit a corpse can be used to estimate PMI. Succession data are useful in providing a minimum and maximum estimate of time since death. However, biotic and abiotic factors are known to influence carrion insect growth and activity and need to be considered when estimating PMI (Wells and Lamotte 2001). 

In view of their critical importance in regulating the growth and development of insects, the enzymes should continue to be viewed as potentially valuable targets around which to develop new pest control agents. This possibility is likely to become more realistic as the enzymes are further characterized and the full extent of their many roles in insect development are more fully understood. 

Resistance of vTKM6f plants to SSB is probably due to the production of certain allomones which inhibit oviposition and disrupt the insect s growth and development. Some of these factors, such as compound A, have recently been identified and synthesized in collaboration with the Tropical Development Research Institute (formerly Tropical Products Institute), London (20). The allomones in the resistant TKM6 variety thus account for inhibition of SSB oviposition and for adverse effects on egg (embryonic), larval and pupal (post-embryonic) stages. On the other hand, nine wild rices (four . minuta J.S. Presl., four 0 officinalis Wall ex. Watt, and one (). punctata Kotschy ex. Steud.) had no compound A in their plant volatiles, but a few were still toxic to SSB (21). This confirms that allomones other than compound A may also be involved in SSB resistance. The role of nutritional factors in growth of SSB larvae remains yet to be studied. 

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