Not just the cones: Dioryctria mendacella (Lepidotera Pyralidae) also attacks grafted pine shoots

The pine cone moth, Dioryctria mendacella Staudinger, is one of the most important pests affecting cones of Mediterranean pines in Portugal and in southern Europe. The females lay eggs on pine cones where the larvae cause damage to tissues and seeds resulting in deformations, abnormal growth, cone abortion and seed loss. Attacks of D. mendacella are restricted to cones, but in the spring of 2021, an unusual infestation by Lepidoptera larvae in the grafted shoots of young Pinus pinea L. trees was observed in Coruche, Portugal. Pine shoots exhibited resin exudation, frass, wilting and drying of the scion and the upper stock. Shoots were collected and taken to the laboratory, and emerging adult moths were identified as D. mendacella by morphological (including genitalia observations) and molecular analysis. We recorded 49.5% of failed graftings and considering nearby plantations (in the absence of insect attacks) we estimated D. mendacella was responsible for around 17% of the grafting failure. Cones collected from pines within the plantation showed no insect attack. We discuss why this pine cone moth population may have adopted this new feeding habit, and its possible implications to modern stone pine silviculture where grafting is a frequent technique.