Cone- and Seminiphagous Insects of Fir Abies alba Mill. in Selected Localities in Roztocze National Park in the Yeas 1982-1986

1988

S. 3-16

1 Abb., 4 Tab., 10 Lit. Ang.

Unselbständiges Werk

200048409

In the years 1982-1986 experiments were carried out on the insects found in the cones of fir Abies alba Mill. originated from the Roztocze National Park in south-eastern Poland. A total of 1,063 cones were collectedfrom 61 growing trees. Analyses of 489 immature cones with a total of 163,378 seeds were performed by means of cutting method to define infestation rate of the cones by insect larvae. Also by cutting method were analysed 5,700 ripe seeds, to estimate those infested by the insect larvae. Individual and mass cultures were established from the larvae found during analyses and from those collected in the cones. Based on the results obtained following conophagous insects were found: Barbara herrichiana Obr. (Lep., Tortricidae) , Dioryctria abietella (Den. et Schiff.) (Lep. Phycitidae) and Earomyia impossibile Morge (Dipt., Lonchaeidae) and seminiphagous insects: Megastigmus suspectus Borr. (Hym., Torymidae)and Resseliella piceae Seitn. (Dipt., Cecidomyiidae) (a total of 19,650 specim ens). The most numerous proved to be E. impossibile - 7,347 specimens whichconstitutes 37,4% of all the insects obtained. Also numerous were R. piceae - 6,610 specimens (33,6%) and M. suspectus - 5,266 (26.8%). The remaining speciesmentioned in Table 3 were rare. Throughout the study period R. piceae caused h eaviest losses in the seeds. The number of seeds injured by this insect amounted to 10,584 which accounts for 6.6% of the total number of examined seeds. Fiveper cent of seeds were destroyed by E. impossibile. The percentage of seeds da maged by the rest of insects was given in Table 2. Analyses of ripe seeds showed that the annual mean percentages of the seeds injured by M. suspectus were inthe range from 0.3 to 47.7; averaging 13% in the study period. Distinct fluctu ations of the number of insects, obtained from the same locality intwo replications, were found. That is indicative of the dynamics of populations of cono- and seminiphagous insects throughout years. A hitherto unknown parasitoid of Megastigmus suspectus larvae was found and identified as Mesopolobus pinus Hussey (Hym., Pteromalidae). Also were estimated parasitoids: Actia nudibasis Stein. (Dipt., Tachinidae) (host - Barbara herrichiana) and Townesia tenuiventris Holmgr. (Hym., Ichneumonidae) (presumably host - Dioryctria abietella). A strict correlation was found between the number of speciments of the studies pests, and the location of fir-tree in the stand from which cones were collected. Fir-trees growing near the border of the stand have shown an almost double intensity of cone infestation by insect pests than those inside the stand.