Studies on the biology and ecology of the egg‐parasites (Hym.: Chalcidoidea) of the pine sawfly Diprion pini (L.) (Hym.: Diprionidae) in Central Europe

Abstract

As a supplement to our earlier paper on the egg parasites of Neodiprion sertifer (Pschorn‐Walcher and Eichhorn 1973), the biology and ecology of the same four species of egg parasites in association with the common pine sawfly Diprion pini (and some of its relatives) is described. The dominant egg parasite is Achrysocharella ruforum, whereas A. ovulorum, Dipriocampe diprioni and the hyperparasite Tetrastichus oophagus are relatively rare. The phenology, voltinism, and synchronization with the host through the intervention of a photoperiodically controlled, eonymphal diapause and the adoption of a facultatively hyper‐ or auto‐parasitic behaviour in Achrysocharella spp. are discussed. The oviposition pattern of A. ruforum and D. diprioni in egg clusters of D. pini is shown to be more or less random, in contrast to the aggregated pattern found in the other gregarious species of pine sawflies, and it is suggested that this difference is due to the partial protection of D. pini eggs provided by the froth‐like substance covering them. The effect of the egg parasites on low, endemic populations of D. pini is thought to be rather limited, average egg parasitism being usually around 15%, but ‐ as literature records indicate ‐ the efficacy, especially of A. ruforum, might be greater at higher host densities. Zusammenfassung Studien zur Biologie und Ökologie der Eiparasiten der gemeinen Kiefernbuschhornblattwespe, Diprion pini (L.), in Mitteleuropa In Ergänzung zu Untersuchungen über die Eiparasiten der rotgelben Kiefern‐Buschhornblattwespe, Neodiprion sertifer Geoff. (Pschorn‐Walcher und Eichhorn 1971, 1973), wurden in den Jahren 1968–1975 Untersuchungen über die Eiparasiten der gesellig lebenden Kiefern‐Buschhornblattwespen Diprion pini L., Gilpinia socia Klug, G. pallida Klug und Microdiprion pallipes Fallén durchgeführt.Das Material wurde in 9 Regionen (24 Lokalitäten) in 6 europäischen Ländern gesammelt. Es wurden die gleichen 4 Erzwespenarten als Eiparasiten der Gattungen Diprion, Gilpinia und Microdiprion festgestellt wie bei N. sertifer, nämlich Dipriocampe diprioni Ferr., Achrysocharella ruforum Krausse, Achrysocharella ovulorum Ratz, und Tetrastichus oophagus Otten. Von insgesamt 3869 Eiparasiten, die aus Eiern von D. pini gezogen wurden, waren 82,0% A. ruforum, 7,9% A. ovulorum, 6,9% D. diprioni und 3,2% T. oophagus. A. ruforum ist daher der einzige Eiparasit, der als biologischer Begrenzungsfaktor Bedeutung hat. Was die Konstanz der Eiparasiten betrifft wurde folgendes festgestellt: In 61 Proben, die 1968–1971 in 24 Lokalitäten gesammelt wurden, kam A. ruforum in 91,8% vor, A. ovulorum in 64,0% D. diprioni in 42,6% und T. oophagus in 22,4%. A. ruforum tritt vorwiegend primär, gelegentlich auch als Sekundärparasit auf. Die Art überwintert in Eiern von D. pini, G. socia und G. pallida als erwachsene Larve (Eonymphe), selten als Puppe. Die Adulten der überwinternden Generation schlüpfen in Delémont (500 m über NN) von der zweiten Aprilhälfte an bis Ende Juli mit zwei ausgeprägten Schwerpunkten (1973: Anf...

Does egg deposition by herbivorous pine sawflies affect transcription of sesquiterpene synthases in pine?

“…The sawfly D. pini (Hymenoptera, Diprionidae) was reared in the laboratory on pine branches as described by Bombosch and Ramakers ( 1976 ) and Eichhorn and Pschorn-Walcher ( 1976 ) at 25 ± 1°C, 65% RH, and 18:6 h light/dark cycles. The egg parasitoid C. ruforum (Hymenoptera, Eulophidae) was collected in the field in southern Finland.…”

“…We addressed this question by studying Pinus sylvestris (Scots pine), a species that changes its odor locally and systemically in response to egg deposition by the pine sawfly Diprion pini. An egg parasitoid, the eulophid wasp Chrysonotomyia ruforum which may significantly limit sawfly populations, is attracted by the oviposition-induced odor of Scots pine (Eichhorn and Pschorn-Walcher 1976 ; Hilker et al 2002b , 2005 ). The sawfly female slits a needle longitudinally with her sclerotized ovipositor valves and lays eggs into the slit.…”

Interspecific extrinsic and intrinsic competitive interactions in egg parasitoids

“…It was found that, when exposed to S,R,R-tridecyl acetate or to S,R,R-proprionate, both parasitoid species showed a similar reaction spending significantly longer time in the test odor arm than in the three control ones. Even if both parasitoids display similar responses to host sex pheromone components, parasitism level by C. ruforum is higher in the field (Eichhorn and Pschorn-Walcher 1976). We suppose that these findings are likely to be related with the ability of C. ruforum to develop as a facultative hyperparasitoid of D. diprioni especially during the early season when the availability of unparasitized host eggs is scarce.…”

Biological Control ofFenusa pusilla(Hymenoptera: Tenthredinidae) in the Northeastern United States: A Thirty-Four Year Perspective on Efficacy

“…When high proportions of tree leaves are mined, browning makes ornamental birches unsightly, although damage does not normally cause tree death. Investigations on natural sources of mortality associated with the pest in Connecticut (Friend 1933) and Quebec (Cheng & LeRoux 1965, 1969, 1970 showed that parasitism of larvae was insignificant (<5%) compared to the situation in the its na-tive range in central Europe, where parasitism was much higher (38-47%) (Eichhorn & Pschorn-Walcher 1973). This difference prompted the initiation of classical biological control programs in both Canada and the USA, leading to the release of 4 parasitoids: the ichneumonids Lathrolestes nigricollis (Thompson) and Grypocentrus albipes Ruthe, the braconid Phanomeris sp., and the eulophid Chrysocharis nitetis (Walker).…”