Pheromone mortality was recorded within a distance of 50 m around each test trap. The 1978 mortality was classified in two groups: (1) five trees or more killed by the beetles, (2) less than five trees killed. In 1979, records were made on whether or not one or more trees were infested by beetles. About 61 070 of the test trap localities with less than five beetle-killed trees in 1978 had no tree mortality in 1979. Where five trees or more were killed in 1978, 48% of the sites showed no beetle infestation in 1979.

Tree mortality around traps was frequently observed. Many forest owners failed to follow the guidelines for trap locations and placed their traps in the forest stands or too close to the forest edge. Also, the 10 m distance between traps and healthy trees recommended in the guidelines seemed to be too close in areas with a high beetle population. The recommendation for 1980 will be 30m. Learn more about insect suppression with pheromones.


Pheromones in the past 8 years. 2.5 million cubic meters of spruce, (about 7 million trees) were killed by bark beetles in southern Norway. In 1978, about 1.1 million cubic meters were beetle-infested. The Norwegian Civil Forest Administration faced the threat of an increasing bark beetle outbreak. and one of the biggest catastrophes to Norwegian.

FIGURE 2. Mean trap captures at different altitudes in Telemark County in 1979.

Pheromone response might be better in the lowlands due to higher temperatures and a longer flight period.

Pheromone Captures

The spruce bark beetles emerge from the forest floor and have a main spring flight in middle or late May, depending mainly on the air temperature. The flight occurs on warm days during most of the summer.’ Under epidemic conditions, beetles leave their galleries after some days or weeks for a second flight and establish sister broods. The beetles may have two or three sister-brood flights. The temperature during midsummer influences the degree of reemergence and the summer flight activity. Learn more about pheromones at The summer of 1979 was rainy and cold in Norway, and the snow remained until May in inland districts. Initial beetle flight was observed in certain warm sites from the middle of May, but the main spring flight was delayed until May 30 or 31 in most lowland districts, which is later than usual in Norway.’ Flight activity was also re- corded in June. About June 20, the traps had caught 75% of the season total. During the first half of July, there were some days with sister-brood flight, but in mid—July, cold weather mostly terminated flight activity. Trap captures from some experimental plots during summer are shown in Figure 3, separately for the southern coast region and the inland region. Learn about the discovery of pheromones.

Trapping of Nontarget Insects

More than 99% of the insects trapped were beetles of the genus Ips. I. typographus predominated, but a few percent in certain locations were (Sahlberg), which responds to the ipsdienol component of the dispenser. A few budprestids, ela- terids, and ants were found among the bark beetles, but only in insignificant numbers.