I was over at the Turnditch orchard this afternoon applying Vitax fruit tree grease to the trunks of the fruit trees. The stuff is spread in a 100 cm band around the trunk at a height of approximately 40 cm. It helps to keep wingless parasites from climbing up the trunk to lay their eggs in the Winter. Notably the main such parasite is the Winter Moth, whose caterpillars can cause a lot of leaf damage in the Spring. In the summer the grease also keeps ants away from the trees. The ants "farm" aphids in the trees and protect them from predators such as Ladybirds. Once the ant pathways up the tree trunk are blocked the parasites such as aphids tend to disappear as the flying predators operate unhindered.
The grease is black and very sticky. It is made from Rapeseed Oil (canola).
Talking of parasites, I found the "missing" quince fruit in the orchard. It was laying in the grass about 30 metres from the quince tree. A bite had been taken out from one side of the fruit, it looks like the bite of a juvenile human. An education for them perhaps? Quince grown in this country are generally hard, very tart, and almost inedible until cooked.