Studies on the occurrence and parasitization of the spruce seed pests, <i>Megastigmus strobilobius</i> Ratz. (Hym., Torymidae) and <i>Plemeliella abietina</i> Seit. (Dipt., Cecidomyiidae) in Poland during a poor seed year

The cone entomofauna of native Norway spruce was compared to that of 28 exotic spruce species introduced in 2 French arboreta. Thirty‐two insect species, including 12 phytophagous, have been observed. Most of them were native to Norway spruce. The seed wasp Megastigmus atedius was the only phytophagous pest introduced with its hosts from North America. It was recorded for the first time in France. The number of insect species that colonized cones was directly related to the phylogenetic and geographic proximity of the exotic spruce from Picea abies and to its flowering phenology. Early‐flowering spruce species of abies group, originating from Hymalaya and central China, were the most attacked by insects, followed by Euro‐Caucasian species of omorica group. Host range observed in each phytophage showed that damage was the more related to spruce phylogeny as insects were specialized in cone exploitation. The importance of entomological studies in arboreta was clearly demonstrated, as evidenced by the potential for native insects to shift to exotic species and the detection of introduced seed chalcids. Résumé Les dégâts d'insectes des cônes sur les Conifères exotiques introduits en arboretum. I. Variations interspécifiques au sein du genre Picea La colonisation par les insectes des cônes de 28 espèces exotiques d'épicéas introduites dans 2 arboreta français a été étudiée en référence à la faune entomologique connue sur l'essence native, l'épicéa commun. Trente‐deux espèces d'insectes, incluant 12 ravageurs phytophages, ont été observées. Un seul de ces phytophages, chalcidien des graines nouveau pour la faune de France, a été introduit avec son hôte depuis l'Amérique du Nord. Les autres espèces appartenaient à la faune autochtone des cônes d'épicéa. L'importance de la colonisation des essences exotiques dépend de leur proximité phylogénétique et d'origine géographique vis‐à‐vis de Picea abies, ainsi que de leur précocité de floraison. Les essences à floraison précoce du groupe abies, d'origine hymalayenne et de Chine centrale, sont les plus attaquées globalement, suivies par les essences euro‐caucasiennes du groupe omorica. L'étude du spectre de colonisation de chaque espèce d'insecte montre que ce lien avec la phylogénie du genre Picea est encore plus accentué chez les insectes spécialistes. L'intérêt des études entomologiques dans les arboreta est finalement mis en évidence, notamment pour un inventaire précoce des potentialités des insectes autochtones à passer sur les essences exotiques et pour la découverte de ravageurs des graines nouvellement introduits. Zusammenfassung Über Insektenschäden an Zapfen exotischer, in Arboreten angebauten Koniferenarten. 1. Interspezifische Variationen in der Gattung Picea Es wurde die Entomofauna der Zapfen der einheimischen Norwegischen Fichte, Picea abies, mit jener von 28 exotischen Fichtenarten, die in 2 französischen Arboreten eingeführt worden waren, verglichen. Dabei wurden 32 Insektenarten festgestellt, darunter 12 Phytophagen, von denen die meisten an der Norw...

Section: Cydia Strobilella (Tortricidae)supporting

confidence: 87%

Insect damage to cones of exotic conifer species introduced in arboreta

Ros

Ostermeyer

Roques

et al. 1993

“…At least in some parts of Switzerland, infestation rates of P. abietina equalled or exceeded those of C. strobilella , but this gall midge caused only about half of the absolute and relative seed losses per cone. In other countries such as Finland (A nnila , 1966), France (R oques , 1983) or Poland (S krzypczyńska , 1989), P. abietina is referred to as a rather rare species with infestation rates sporadically rising up to 20%. A nnila (1984) found, that this species exploits seeds only during years of heavy to medium crop, whereas in Switzerland the crop size was quite small in the two years under study.…”

Section: Discussionmentioning

confidence: 99%

“…

In 1989 and1990, spruce cones were harvested at 29 sites distributed over the ®ve main geographic regions of Switzerland, i.e. Jura, Central Plateau, North, Central and South Alps.

…”

mentioning

confidence: 99%

The effect of spruce cone insects on seed production in Switzerland

Seifert

Wermelinger

Schneider

2000

In 1989 and 1990, spruce cones were harvested at 29 sites distributed over the five main geographic regions of Switzerland, i.e. Jura, Central Plateau, North, Central and South Alps. The presence of insects and the species‐specific consumption of seeds was determined for each cone by examination of the median longitudinal section. Seven seed‐feeding species (Assara terebrella, Cydia strobilella, Dioryctria abietella, Eupithecia abietaria, Megastigmus strobilobius, Plemeliella abietina, Strobilomyia anthracina) and the spruce cone gall midge Kaltenbachiola strobi were found in the samples. The proportions of infested cones ranged from 36 to 100%. The regions did not show significant differences in terms of infestation rates, whereas differences between sites within the regions were highly significant. Seed loss ranged from 2 to 100%, its geographical distribution exhibiting a similar pattern to the infestation rates. Considering the number of infested cones, C. strobilella was the most abundant species, followed by K. strobi and P. abietina. Cones infested by conospermatophagous species (C. strobilella, D. abietella, E. abietaria) showed higher seed losses than those infested by spermatophages (M. strobilobius, P. abietina). Due to the ubiquitous occurrence of C. strobilella, its high infestation rates and the resulting seed losses caused by its offspring, this species has to be considered as the most important insect seed predator in Switzerland. A multiple linear regression analysis was carried out for each region to simultaneously explore the impact of site and tree variables as well as the effect of insect attack on the yield of viable seeds. The results indicate that site and tree conditions contributed more to the variability of seed yield than insect presence in a cone. The model predicted significant effects of insect attack mainly for cones with total seed numbers that were higher than the average.

“…Probably the greatest damage caused by this species occurred in the higher levels of the upper montane zone where the greatest numbers of K. strobi occurred in cones, and empty seeds were most numerous. Infestation of spruce cones by K. strobi in the Tatra National Park turned out to be exceptionally high, and in excess of levels reported from any other part of Poland (SZMIDT, 1953;MADZIARA-BOR-USIEWICZ, 1961;SKRZYPCZYN Â SKA, 1982, 1985, 1989, 1994. In total, this pest inhabited 89.10% of analysed cones.…”

Section: Discussionmentioning

confidence: 80%

“…In Poland, pests of cones and seeds of spruce were investigated ®rst of all in the Beskid Sadecki Mountains (SKRZYPCZYN Â SKA, 1982), Babia GoÂ ra National Park (SKRZYPCZYN Â SKA et al, 1994), and in the north-eastern range of spruce (SKRZYPCZYN Â SKA, 1989). Very little investigation in this respect was carried out in the Tatra National Park, which is one of the largest and most valuable spruce mountain stands in Europe (BIAL / OBOK and BARTKOWIAK, 1967).…”

Section: Introductionmentioning

confidence: 99%

Cono‐ and seminiphagous insects of Norway spruce Picea abies (L.) Karst. and their parasitoids in lower and upper montane zone of the Tatra National Park in Poland

Kozioł

2000

A study of the insects inhabiting of cones of Norway spruce Picea abies (L.) Karst. in the Tatra National Park was conducted during 1987±92. As a result of breeding and analyses of the cones collected from trees at various altitudes above sea level, 53 746 specimens of cono-and seminiphagous insects were collected. Interior damage to cones and the losses of spruce seeds caused by pests were measured, with regard both to the variable cone crop abundance of spruce and to different altitudes above sea level. The role of parasitoids in limiting the numbers of some cono-and seminiphagous insects was also estimated. U. S.