Multiple leaders caused by the tarnished plant bug (Lygus rugulipennis) in Picea abies seedlings

Abstract

Feeding by the tarnished plant bug (Lygus rugulipennis Popp.) has caused severe damage in Norwegian nurseries. Large quantities of seedlings have been removed after sorting. The life cycle of the insect has been well studied and documented. This study was a first attempt to investigate how the seedlings develop after the insect attacks. The first visible sign of damage is the development of multiple terminal buds. Two-year-old containerized seedlings were planted and followed for 4 years. Before planting, the seedlings were sorted into three damage classes: 0, undamaged; I, moderately damaged, up to 10 fully developed buds; and II, severely damaged, 10–20 small buds and no dominant apical bud. The damaged seedlings were somewhat shorter at planting but this difference disappeared with time. The seedlings in the two damage classes differed in their development of multiple shoots. At the end of the 4 year period about 50% of the seedlings in class II and about 20% from class I still had multiple leaders, or lateral stems or side branches that would probably produce spike knots in the future. The sorting routine currently used at the nursery was found to reduce the problem to an acceptable level for seedlings that were planted in the forest.

Keywords:

• Lygus rugulipennis
• multiple leaders
• Picea abies
• ramicorn branches
• seedling performance

This study was supported by the Norwegian Forest Research Institute. Useful assistance was provided from the leader of Telemark Forest Nursery, Mr Kittil Dyrud and his staff. Good advice has been given by my colleagues and not the least, the referees.