Assessment, Conservation and Sustainable Use of Forest Biodiversity

Assessment, Conservation and Sustainable Use of Forest Biodiversity
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INFLUENCE OF CHEMICAL TREE INJECTION ON POPULATIONS OF BARK
BEETLES IN YOUNG SPRUCE AND PINE STANDS
Rostislav Vlasov* and Igor Shutov
Forestry Research Institute, 21 Institutsky pr.,
194021 St. Petersburg, Russia
E-mail: spb330@spb.sitek.net
Keywords: Scolytidae, spruce, pine, injection, glyphosate
Introduction
Restoration of primary (original) forest vegetation types having unique biodiversity is a very important task.
This work, as a rule, is impossible to fulfil without removal a part of invasive secondary plants. Elimination of
undesired vegetation is feasible through the use of effective modern chemicals (Egorov 1989, Martynov et al.
1998). Such a measure is suitable only if it does not cause different negative consequences, including outbreaks
of biological organisms able to destroy existing phytocoenoses. In our case, thinning experiments were
conducted to study influence of arboricide injection into stems of coniferous trees on bark beetles’
(Coleoptera: Scolytidae) attack behaviour. In such cases, the danger of bark beetle outbreak can arise in an area
having large numbers of arboricide-treated trees dying. In addition, bark beetles can move to surrounding
stands. We should know if there is a danger to the remaining healthy trees in the stand. Also, the questions of
forest protection should be discussed in the case of bark beetles’ successful development in treated trees and
subsequent colonisation of healthy trees.
Methods
The study was conducted in Siversky Experimental Forest, about 70 km south of St. Petersburg, Russia. Several
20- to 39-year-old Norway spruce, Picea abies (L.) Karst., and Scotch pine, Pinus sylvestris L., plantations
growing on good sites were chosen for the study. The reason for selection was because these stands needing
precommercial thinning appear to be most susceptible to bark beetle attacks due to tree size. The total area was
1 ha for spruce and 1 ha for pine experimental plots. Diameter at breast height (DBH) ranged 3-12 cm for
spruce and 4-14 cm for pine. The arboricide Roundup® (active ingredient glyphosate) was injected into the
stems of pine and spruce trees on the experimental plots. Felling, mechanical girdling (by removal of a
complete bark belt from the tree), and plots without any treatment served as controls. A total of 1100 spruce
and 300 pine trees were subjected to different treatments. Pheromones were not used to attract bark beetles
into the plots. In all experimental stands and plots with chemical treatment, 1 to 3 spaced frills (notches) were
made per experimental tree to be treated, depending on the tree diameter, with a hand hatchet at
approximately 1 m above the ground. The arboricide was applied at the rate of 1 ml per frill with a plastic
squeeze bottle. Strength of the arboricide, the number of frills per a tree, and the rate of arboricide application
followed recommendations by Egorov (personal communication). Treatments were carried out in mid- to late
August 1997, 1999, and 2000.
The experimental plots were examined and sampled for bark beetle activity next year after treatment. In each
plot, 5 sample trees (attacked by bark beetles) were taken randomly in late August. Three 25-cm-long sample
bolts for spruce bark beetles (50-cm-long for pine bark beetles) were taken from the infested part of each
sample tree. First, exit holes of bark beetles were counted in each sample bolt. Then bark was removed from
each sample bolt to count egg galleries, nuptial chambers and young beetles. The length of all egg galleries in
each sample bolt was measured and beetles found were identified. Population characteristics of bark beetles
such as attack density (that is the number of bark beetle families per 1 dm 2 of bark surface), the number of
parent (males plus females) and young beetles (including exit holes) per 1 dm 2 were determined as described
in Mozolevskaya et al. (1984). Statistical methods were used to analyse results obtained.
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