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Sirvi Autor "Ploomi, Angela (advisor)" järgi

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    The Effects of Natural and Anthropogenic Factors on the Physiological State of Insects
    (Eesti Maaülikool, 2012) Kivimägi, Irja; Metspalu, Luule (advisor); Ploomi, Angela (advisor)
    1. A novel O2 respirometry system termed coulometric respirometry was developed able to record oxygen convective uptakes (passive sucction inspiration) during the F-phase. It is not possible to measure and record these O2 uptakes using a flow-through respirometry system. It was found that the F-phase begins immediately after the end of O-phase. The convective O2 uptakes at the beginning of the F-phase did not allow the emission of CO2 and water vapour. It was demonstrated that when coulometric O2 respirometry and flow-through CO2 respirometry are used alternately more information can be obtained than from each system separately. 2. This work demonstrated that, in carabid beetle Pterostichus niger, the DGE pattern is typical in a dry environment (5% RH), as well as in conditions of high humidity (95% RH). The main prediction of the hygric hypothesis is that, in moist air, DGE is eliminated. In this way, the hygric theory was not supported in this carabid species. Therefore, we give more support to the well-known alternative hypothesis: the O2 damage hypothesis. 3. The results showed that sublethal doses of pyrethoid Fastac 50 EC influence the physiology of beneficial insects. The main effect of pyrethroid was to eliminate cyclic gas exchange of carabid beetle Platynus assimilis and the pattern of continuous gas exchange appeared. After this transformation of gas exchange pattern, water loss increased due to the higher frequency and amplitude of the continuous respiratory contractions. 4. The present work demonstrated significant differences in some biological parameters of cabbage moth Mamestra brassicae larvae and pupae reared on different food plants. Food plants influenced larval developmental rate, larval and pupal body mass, mass loss and the intensity of pupal diapause. Developmental time of larvae was shorter when reared high quality of food plants. Poor quality of larval food plant influenced diapause intensity of pupae. The weakening diapause of pupae caused higher winter mortality. From the results it may be concluded that the effect of the pesticides should not be observable in a short time frame since there is a chance the insect survival is affected subsequently. This is the reason why pest monitoring is required before pesticide application. The elaborated O2 respirometry system termed coulometric respirometry allows to measure even smallest differences caused by numerous factors influencing the physiological state of insect. By this method it is possible to carry out more detailed research about long-term effects of sublethal doses of pesticides including biopesticides on insect. Together with physiological research field studies on availability and quality of host plants are needed in order to accumulate basic knowledge for planning crop layouts within a field and successional cropping/rotational practices from year to year to minimise the success of pest.