%0 Research article
%T Experimental evidence for associational resistance against the European pine sawfly in mixed tree stands
%A Kaitaniemi, Pekka
%A Riihimäki, Janne
%A Koricheva, Julia
%A Vehviläinen, Harri
%D 2007
%J Silva Fennica
%V 41
%N 2
%R doi:10.14214/sf.295
%U https://silvafennica.fi/article/295
%X This study examined whether the saplings of Scots pine (Pinus  sylvestris) exhibit associational resistance against the European pine  sawfly Neodiprion sertifer (Hymenoptera, Diprionidae) when grown in a  mixture with 50% silver birch (Betula pendula). The number of sawflies  on pine trees in pure and mixed stands was manipulated at two  experimental sites during two years. Survival of larvae and eggs was  monitored, and the numbers of presumed sawfly predators were counted. A  lower proportion of sawfly larvae and eggs survived on pines grown in  the mixture with birch as compared with pure pine stands. Lower survival  of sawfly larvae in the mixed stands was associated with the higher  abundance of ants in these stands. The numbers of other sawfly predators  (e.g. spiders and predatory heteropterans) differed between the study  sites and were negatively associated with the presence of ants, which  suggests possible interference between these groups. Although sawfly  survival was lower on pines in the mixed stands, providing evidence of  associational resistance, a related study shows the same trees had a  higher number of ant-tended aphid colonies as compared with pines in the  pure stands. Therefore, instead of considering resistance against  individual herbivore species, it seems more practical to use  associational resistance as a trait representing the resistance of  larger systems, such as whole tree stands, against the total damage  caused by herbivores in general.