Articles by Michael M. Müller

Unequivocal evidence on the antagonistic effects of endophytic fungi associated with woody plants against insect herbivores has been documented in only a few cases so far. Experimental evidence of the significance of needle endophytes to coniferous trees has remained scant because it is difficult to obtain trees with needles free of endophytes that could be used as comparable controls for trees infected with endophytes. Previously we reported a new methodology to get Norway spruce (Picea abies (L.)  Karst.) saplings without needle endophytes and to inoculate them with a needle endophyte Lophodermium piceae (Fuckel) Höhn. Here we describe the first trial where spruce saplings with and without needle endophytes were provided as substrate for insect larvae. We transferred larvae of two sawfly species, Neodiprion sertifer Geoffroy and Gilpina pallida Klug, to the seedlings. Even though the main host of these sawfly species is not Norway spruce, but Scots pine (Pinus sylvestris L.), they are also known to occasionally feed on spruce. In this experiment the larvae did not develop to pupae with the provided spruce substrate but consumed measurable amounts of needles. No significant difference was found between the extent of needles consumed by either of the two sawfly species in inoculated and uninoculated saplings.

• Müller, Natural Resources Institute Finland (Luke), Forest Health and Biodiversity, P.O. Box 2, 00791 Helsinki, Finland https://orcid.org/0000-0003-3699-2139 E-mail: micms.muller@gmail.com
• Hamberg, Natural Resources Institute Finland (Luke), Forest Health and Biodiversity, P.O. Box 2, 00791 Helsinki, Finland https://orcid.org/0000-0002-0009-7768 E-mail: leena.hamberg@luke.fi
• Varama, Natural Resources Institute Finland (Luke), Forest Health and Biodiversity, P.O. Box 2, 00791 Helsinki, Finland E-mail: martti.varama@pp.inet.fi

We investigated the causative agent of a disease outbreak affecting small-leaved limes (Tilia cordata Mill.) and resulting in darkening of the leaf petioles and excessive defoliation during summer 2016 in southern Finland. The fungal species composition of the symptomatic petioles was examined by culture isolation and molecular identification using ITS rDNA sequences, which revealed the most prevalent fungal species present in the petioles as Apiognomonia errabunda (Roberge) Höhn. Based on reviewing curated herbarium specimens deposited at the Universities of Helsinki and Turku, A. errabunda is native and widely distributed in small-leaved limes in Finland, and occasionally infects also other broadleaved trees, including Quercus robur L. and ornamental species of Tilia L. and Fagus L. The ITS sequence analysis conducted during this study revealed minor within-species polymorphisms similar to those observed earlier in the Central European and Russian populations of A. errabunda, and reports the first nucleotide sequences of this species from the Nordic countries.

• Vainio, Natural Resources Institute Finland (Luke), Management and Production of Renewable Resources, P.O. Box 2, FI-00791 Helsinki, Finland http://orcid.org/0000-0002-6739-7968 E-mail: eeva.vainio@luke.fi
• Velmala, Natural Resources Institute Finland (Luke), Management and Production of Renewable Resources, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: sannakajsa.velmala@luke.fi
• Salo, Finnish Museum of Natural History, Botanical Museum, P.O. Box 7, FI-00014 University of Helsinki, Finland E-mail: pertti.salo@helsinki.fi
• Huhtinen, University of Turku, Herbarium, Biodiversity Unit, FI-20014 Turku, Finland E-mail: sephuh@utu.fi
• Müller, Natural Resources Institute Finland (Luke), Management and Production of Renewable Resources, P.O. Box 2, FI-00791 Helsinki, Finland E-mail: micms.muller@gmail.com