The Pine-Gall Midges and their Economic Significance in Northern Germany : Insects Affecting Reforestation. Biology and Damage

1989

S. 224-233

5 Abb., 5 Tab., 6 Lit. Ang.

Unselbständiges Werk

200069391

From 1981 till 1984 there were outbreaks of the fall midges Thecodiplosis brachyntera and Contarinia baeri in Lower Saxony, especially in the eastern parts. 1. In two research areas the attack was low to medium in 1983 and low in 1984. 2. In galls of T. brachyntera only one larva per gall was found, while up to 17 larvae of C. baeri lived in one pair of needles. 3. Until August mortality of both species reached 90%. 4. Needles attacked by T. brachyntera grew to only 30 to 40% of the length of healthy needles. Needle shortening by C. baeri amounted up to 88%. 5. Contarinia baeri preferred the terminal parts of trees, whereas T. brachyntera showed no preference. 6. Especially the highest trees of the research area were attacked by C. baeri. 7. Depending on the intensity of attack in 1983 the sprouts from 1984 were shortened. 8. Replies to a questionnaire sent to the state forest districts in Lower Saxony indicated that a) the centres of attack lay in the eastern part of Lower Saxony; b) Contarinia baeri was more frequent than T. brachyntera (80% to 12%); c) the attack declined from 1983 to 1984; d) 10- to 20-year-old stands were mostly attacked; e) stands with a better supply of water and nutrients were preferred.