Pine woolly aphids secrete white wax-wool on tree stems and branches in which they lay their eggs. S…
Pine woolly aphids secrete white wax-wool on tree stems and branches in which they lay their eggs. Screenshot from video

The Icelandic Forest Service has published a video in collaboration with HealGenCar and SNS, which discusses experiments with various provenances of Scots pine with regard to their resistance to the pathogen pine woolly aphid (Pinus pini). It turns out that the descendants of the small proportion of trees that survived an aphid epidemic in the second half of the last century are least affected by aphids of the material tested.

The pine woolly aphid (Pineus pini) was a major nuisance in forestry in Iceland after the middle of the last century. Scots pine was planted on a large scale in many parts of the country after the Second World War as the star of hope in Icelandic commercial forestry. This changed in a relatively short time when the aphid arrived in the country and began to infest the species. Scots pine stands were largely wiped out by the aphid and for more than half a century, that particular tree species has not been regarded as a promising forest tree in Iceland.

Not all the trees were killed, however, and the occasional pine tree survived the epidemic well, some even faring quite well and forming quite beautiful trees. This severe blow to the Scots pine population in Iceland probably left behind individual trees having the most resistance to the aphid. In other words, a powerful natural selection took place.

A few years ago, an experiment was carried out with Scots pine to see if experience gained and new methods could give new hope for forest forest cultivation in Iceland. The main results of that experiment show that the hardiest and aphid-tolerant Scots pines for Iceland seem to be those grown from the seeds of the trees that survived the previous aphid epidemic in Iceland. The second generation of Icelandic Scots pine is healthy growing and tolerates the aphid better than imported Scots pine material.

The Nidhogg of Scots pine

In a new video published by the Icelandic Forest Service, two of the institution's researchers, Brynja Hrafnkelsdóttir and Lárus Heiðarsson, talk about the experiment in question. Tests were carried out using Scots pine provenances from Norway, Finland, Russia, Scotland and Austria, as well as descendants of Scots pines planted in Iceland which have gone through heavy natural selection attaining resistance to the pine woolly aphid.

The title of the video is Pine Woolly Aphid − Níðhǫggr of Scots pine. Nidhogg (Níðhǫggr in Old Norse) was the Norse serpentine dragon living in the roots of the great ash tree Yggdrasill which holds the 9 realms of Norse cosmology together. Nidhogg also chews on the roots of the tree for all eternity with hopes to damage it and topple it.

The video is produced in collaboration with HealGenCar (Centre of Advanced Research) operating under SNS (Nordic Forest Research), HealGenCar, a temporary collaboration platform for further research in forest health and forest genetics in support of the bioeconomy, actually ran its course at the end of last year. It was succeded by another co-operation platform called Tolerant Tree, which deals with the genetics of trees and breeding in the direction that forest trees can better withstand various challenges faced by them with climate change (Genetics and management for stress tolerant trees for the future climate).

The producer of the video is Kvikland, filming done by Hlynur Gauti Sigurðsson and editing by Kolbrún Guðmundsdóttir.

Texti: Pétur Halldórsson