The aim of this paper is to report on how a complex pathosystem, consisting of the plant (Plantago lanceolata), the weevil (Trichosirocalus troglodytes) and the fungus (Diaporthe adunca) functions in natural populations. In laboratory and garden experiments the weevil has previously been shown to transmit the fungus to the spikes of P. lanceolata, where infection usually starts. However, the interactions of this pathosystem in natural situations were unknown, for example, if the weevil and the fungus occur at the same place and time. To study this as well as the preference of the weevil and the fungus for certain environmental conditions, transects at 23 locations in the Netherlands were laid out. The effect of one of the environmental factors namely the mowing regime on epidemics of the fungus was experimentally tested in a hayfield. A Principal Component Analysis (PCA) showed that weevil and fungus preferred the same habitat. However, the data obtained during two years in 13 permanent transects, showed that the weevil was only active in spring and that the epidemic reached its maximum in autumn. These findings together with additional, circumstantial evidence presented suggest that the weevil does not play an important role in the transmission of the fungus in natural situations. The experiment with the mowing regimes showed that active management can exert an important effect on epidemics of the fungus. The later the vegetation is mown, the lower the level of disease at the end of the season. Late mowing can be seen as having a sanitary effect and might have negative consequences for disease occurrence in the long run. [KEYWORDS: insect herbivore; pathogen; epidemic; PCA; Plantago lanceolata; vector Phomopsis-subordinaria; lawn weeds; major l; disease;variability; genecology]
Original languageEnglish
JournalActa Oecologica
Journal publication date1996

ID: 315936