SOME ASPECTS OF LIFE HISTORY AND POPULATION DYNAMICS OF PISSODES PINIPHILUS HRBST. (COLEOPTERA, CURCULIONIDAE)
TL;DRAbstract
The survival of Pissodes piniphilus was investigated on 60-year-old Scots pines with both healthy-looking and damaged crowns.As the weevils are primary stem attackers, the viable trees kill them in the phase of the eggs or young larvae.They pro- duce new generations only on more weakened trees where the larval mortality is determined not only by the host tree but also by intraspecific competition caused by a high colonization density and entomophages, out of which were more frequently occurent specimens from genera Eubazus, Lonchaea, Medetera.On stems mostly the second-and the last-instar weevils larvae hibernate; their winter dormancy is quite easily terminated by high temperature, but they also acclimate to cold, and this guarantees a sufficient midwinter cold-hardiness of up to -34.5°C.The population increase of P. piniphilus in Estonia is mainly caused by a weakness of the pine stands and temperatures that have been favourable for P. piniphilus development.
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The survival of Pissodes piniphilus was investigated on 60-year-old Scots pines with both healthy-looking and damaged crowns.As the weevils are primary stem attackers, the viable trees kill them in the phase of the eggs or young larvae.They pro- duce new generations only on more weakened trees where the larval mortality is determined not only by the host tree but also by intraspecific competition caused by a high colonization density and entomophages, out of which were more frequently occurent specimens from genera Eubazus, Lonchaea, Medetera.On stems mostly the second-and the last-instar weevils larvae hibernate; their winter dormancy is quite easily terminated by high temperature, but they also acclimate to cold, and this guarantees a sufficient midwinter cold-hardiness of up to -34.5°C.The population increase of P. piniphilus in Estonia is mainly caused by a weakness of the pine stands and temperatures that have been favourable for P. piniphilus development.
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