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soft for quite some time. It has 2-5 year classes of older needles. Nutritional content of the new needles is high: total N
reaches 4.5% dwt, carbohydrate levels 250 nanomoles/g dwt (Jensen 1991). When needles get older, nitrogen levels drop to
around 1%, whereas carbohydrate levels increase somewhat (Table 1).
Table 1.--Concentrations of nutrients and secondary compounds in needles and male flowers of spruce, Picea abies.
Total Amino Shikimic Quinic Pinitol Hexoses Inositol Cathecin Total
Plant .part Nitrogen acids acid acid Phenolics
% ................... n moles/mg dwt ...................
Male flowers 5 _900 29 213 134 575 18 4
Old top needles 1.2 _450 224 52 61 390 7 12 68
New top needles 4 1,t20 108 625 133 248 17 3 35
In Europe a substantial number of insect species are flush-feeders on spruce although some of them also consume
older foliage, especially late in year or at outbreak densities (Table 2). This situation mainly applies to Lepidoptera although
certain sawfly species also are flush-feeders. Another group feeds exclusively on older needles and is mainly comprised of
Hymenoptera. In general, most spruce flush-feeders (e.g., L. monacha) perform substantially better when reared on the new,
nutritious needles than on the old ones. Most newly hatched larvae die when put on old needles probably because their
mandibles are not strong enough to cope with the hard needles (Jensen 1992). On the other hand, if third instar larvae are put
on old needles, they survive and perform reasonably well. Preference indices for new needles (Table 3) decrease with instar
number, indicating that larger larvae do not require young needles.
Table 2.--Needle age preferences of insect larvae feeding on Norway spruce, Picea abies.
Needle age class
Insect species Newly flushed Current Old
Lepidoptera
Parasyndemis histrionana * (*) _'
Eana argentata * * (*)
Epinotia tedella (*) *
Epinotia nanana * * (*)
Epinotia pygmaea *
Zeiraphera ratzeburgiana *
Orgya antiqua * * (*)
Lymantria monacha * * (*)
Hymenoptera
Cephalcia abietis *
Cephalcia arvensis * *
Gilpinia hercyniae *
Pristiphora abietina *
Pristiphora ambigua *
Pristiphora saxeseni * (*)
Pachynematus scutellatus * * (*)
" * indicates unequivocal primary preferences, (*) indicates secondary preference, often by late instars.
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