• K S S Nair

      Articles written in Proceedings – Animal Sciences

    • Role of behavioural studies in the development of management strategies for forest insect pests

      K S S Nair

      More Details Abstract Fulltext PDF

      Under forestry conditions, management techniques aimed at maintenance of pest populations at moderate levels have greater chance of success than conventional methods of pest control. Simple behavioural observations can sometimes be used to great advantage in the development of such methods, some examples of which are given. Although there has been considerable excitement over the past two decades on the possibility of using behaviour modifying chemicals for control of pests through mass trapping or disruption of the insect’s normal communication systems, no significant practical achievement has so far been reported. Difficulties in the use of these chemicals include inadequate information on the biological responses of natural populations of insects; utilization by most insects of a complex pheromone system involving several chemical components; non-reproducibility of laboratory results under natural conditions due to several modifying factors; high cost of the development and deployment of pheromonal control systems, particularly for low value forestry crops; inadequacy of pheromonal control methods for coping with the high epidemic densities of most forest pests; and the possibility of development of pheromone resistance. Behaviour-modifying chemicals, such as food lures, sex pheromones and population aggregating pheromones, however, are useful in pest management as tools for survey and ecological research. Populations generally exhibit properties that cannot be understood by studying individual insects; study of the behaviour of populations is therefore more important than study of the behaviour of individuals for developing management strategies.

    • The teak defoliator,Hyblaea puera: Defoliation dynamics and evidences for short-range migration of moths

      K S S Nair V V Sudheendrakumar

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      In teak plantations at Nilambur, Kerala,Hyblaea puera Cramer (Lepidoptera, Hyblaeidae) caused one or two waves of epidemic defoliations between late April and July, followed in some years by isolated, lighter defoliation between August and November. The insect was absent at other periods, although with a 3-week life cycle it can theoretically pass through several generations per year. The temporal and spatial distribution of infestation and certain behavioural characteristics of populations gave evidence of short-range migration of newly emerged moths. In a model proposed for population dynamics ofH. puera, no diapause occurs and a residual, non-migratory population exists in natural forests during the nonepidemic period. With the onset of general flushing of teak in February–March, the population starts building up and when a critical density is reached, migratory behaviour is triggered. Migration facilitates exploitation of new food sources and escape from larval parasites. Generally, after one or two epidemics, the population declines due to leaf maturity, natural enemies and density-dependent food depletion. This cycle of ups and downs, with attendant transition between migratory and non-migratory phases is repeated every year. If some steps of the proposed model are confirmed by further study, simple methods could be devised to manage this serious pest of teak.

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