Articles containing the keyword 'herbivore'

The effects of forest fertilizers on the intensity of damage caused by two curculionid (Brachyderes incanus L., Brachonyx pineti Paykull) and two chrysomelid (Calomicrus pinicola Duft., Cryptocephalus pini L.) species feeding as adults on Scots pine (Pinus sylvestris L.) needles were investigated in two pine stands growing on dry (Calluna type) sites in South-West Finland. There was much variation in the abundance of the insect species both between the trials and the sample plots. Nitrogen fertilization increased both the height and radial growth of the pines. The curculinids were slightly more abundant on the nitrogen-treated plots. Potassium application seemed to decrease the feeding intensity of the chrysomelids especially. The overall effects were so small that forest fertilization cannot be considered as an effective control method against needle-feeding beetles.

The PDF includes an abstract in Finnish.

• Heliövaara, E-mail: kh@mm.unknown
• Löyttyniemi, E-mail: kl@mm.unknown

Quantitative variation in the elemental composition of living Scots pine needles was studied along an atmospheric pollutant gradient in the surroundings of the industrial town Harjavalta, south-western Finland. Two 9-km-long transects, each with nine sample plots, running to the S and SW from factory complex were delimited in a homogenous Scots pine (Pinus sylvestris L.) forest. Needle samples were taken from 10 trees at each site, and from two separate sites in Tuusula near Helsinki. There was considerable spatial variation in the elemental composition of the needles. Heavy metals (Cu, Fe, Zn) showed a clear pattern of exponentially decreasing concentration with increasing distance from the emission source. Sodium and potassium concentrations, as well as the ash weight and air-dry weight, also decreased. Magnesium, manganese and calcium concentrations increased with increasing distance.

The PDF includes an abstract in Finnish.

• Heliövaara, E-mail: kh@mm.unknown
• Väisänen, E-mail: rv@mm.unknown

Succession of insect attacks on young Scots pine (Pinus sylvestris L.) was studied in heavily, moderately and slightly polluted pine stands within a three-kilometre distance from a prominent emission source in Western Finland. The total number of pest species was highest in the moderately polluted stand, but unlike other herbivores, aphids were also abundant in the heavily polluted stands. A few positive but no negative interactions were detected between herbivores, which suggests that insect species may benefit from a previous occurrence of other species in the same tree.

The PDF includes an abstract in Finnish.

• Heliövaara, E-mail: kh@mm.unknown
• Väisänen, E-mail: rv@mm.unknown

Adult pine weevils (Hylobius abietis (L.)) feed on the tender bark of branches and roots of mature conifer trees and on the stem bark of conifer seedlings. Their feeding on mature trees does not cause any economic damage, but their feeding on planted seedlings is so devastating that the pine weevil is considered one of the most important forest pest insects in Europe. We asked whether the pine weevil prefers seedlings over other regularly utilized food sources. This question is of particular interest because new approaches to seedling protection are based on decreasing any preference for seedlings by using less palatable plants or by enhancing their defence (by genetic selection or by methyl jasmonate treatment). In a laboratory choice experiment we tested pine weevil feeding preferences for seedlings compared with branches and roots from mature trees (separately for Norway spruce and Scots pine). Pine weevils preferred roots, but not branches, of Norway spruce over seedlings of the same species. With Scots pine there were no clear preferences, but the weevils showed a tendency to prefer roots over seedlings. These results provide support for seedling protection approaches that attempt to redirect pine feeding from planted seedlings to other food sources.

• Fedderwitz, Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, SE-750 07 Uppsala, Sweden E-mail: frauke.fedderwitz@slu.se
• Björklund, Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, SE-750 07 Uppsala, Sweden E-mail: niklas.bjorklund@slu.se
• Ninkovic, Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, SE-750 07 Uppsala, Sweden E-mail: velemir.ninkovic@slu.se
• Nordlander, Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, SE-750 07 Uppsala, Sweden E-mail: goran.nordlander@slu.se