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Egg distribution and survival of Cinara pilicornis (Hartig) (Hom., Lachnidae) on damaged and undamaged Norway spruce (Picea abies) (L.) Karst
The spruce shoot aphid (C. pilicornis) (Hartig) lives on Norway spruce (P. abies (L.) Karst.) and deposits its overwintering eggs on current year needles. Ovipara density and the distribution of their eggs on trees at two different sites of the Fichtelgebirge (north-east of Bavaria), with host trees showing either heavy symptoms of needle-yellowing (Oberwarmensteinach) or look green and healthy (Waldstein) is investigated. In addition, winter mortality of eggs and egg development until birth of the fundatrices is followed. Host plant quality does not seem to influence the proportion of eggs surviving to spring. Also, the biomass of developing first instar larvae of the fundatrices was independent of the degree of needle yellowing. However, significantly more eggs/shoot and eggs/twig were found on hosts without growth disturbance which is due to a higher ovipara density and a higher fecundity of individual ovipara. Damaged or stressed trees do not seem to be better hosts for C. pilicornis. A significant correlation was found between the biomass of first instar larvae of fundatrices and the time of egg hatching. The high phenotypic plasticity of C. pilicornis on good quality plants is discussed and potential implications for forestry are assessed.
ISSN : 0931-2048
Journal of applied entomology (1986) A. 1997, vol. 121, n° 2, pp. 71-75 [bibl. : 36 ref.]
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