Report from the Sub-committee on Agriculture

7. Present production in forestry

7.1 Present production and use of pesticides
7.2 Wood-producing forestry
7.3 Ornamental greenery
7.4 Conclusion

Private forests contra state forests

The sub-committee has only analysed production within private forestry, which covers an area of around 300,000 ha. There is already a plan for phasing out pesticides within state forestry before the year 2005, and the economic consequences of a ban on the of use pesticides on National Forest and Nature Agency Land have been analysed (Linddahl, 1996). State forests cover a total area of 108,000 ha. In this analysis, the economic loss in the case of ornamental greenery has been calculated to be 70% of the present profit, while the additional costs have been found to be 30%.

7.1 Present production and use of pesticides

Table 7.1 shows the distribution of land for production in private forestry. Approximately 11% of land in Denmark is forested.

Table 7.1
Distribution of land used for private forestry production, together with production value

¹⁾ Covers both Norman fir and Abies nobilis.

Small pesticide consumption

Pesticide consumption in forestry has always been very low compared with farming, market gardening and fruit growing. In 1994/95, consumption in the entire forestry sector, including the State forests, was calculated to be as follows:

This consumption amounted to approx. 1% of the total consumption in all sectors of agriculture.

Pesticide consumption is generally higher in private forestry than in state forestry because a larger part of the acreage is used for production of Christmas trees and ornamental greenery. In State forestry, average consumption is estimated to be 0.35 kg gs/ha/year for afforestation and 0.42 kg gs/ha/year for Christmas trees and ornamental greenery.

Pesticides are used in the establishment phase

Pesticides are mainly used in the culture phase in forests and in afforestation areas and areas with ornamental greenery. It is principally herbicides that are used in the establishment phase, when the main problem is controlling grass. Besides this, there is a small consumption of insecticides in ornamental greenery, principally to control common spruce aphid and periodical occurrences of moths. In the establishment phase of conifers, insecticides are also used against weevils.

In the past 20-30 years the production of Christmas trees and ornamental greenery has become of increasing importance for the entire forestry sector. Today, the economy of many forest properties depends on this production (Østergaard et al., 1998).

Problems with grass weed

Grass weed is the predominant problem in forestry. Inadequate control, or none at all, would create a number of problems:

	Grass is a serious competitor for the available water, and in dry years and on poor soil, grass will always win the battle for water.
	Grass shades and lays itself on top of small plants when it dies down, thereby smothering them.
	Grass increases the risk of frost damage because it prevents heat from being given off from the soil. Some species of tree are killed by frost, while growth is retarded in others.
	Grass attracts mice, which can damage the trees by gnawing.
	Grass takes nutrition, which – all else being equal – means an increased need for fertilisation in cultures that are overrun by grass. Swardy soil causes yellowing of ornamental trees and Christmas trees.

7.2 Wood-producing forestry

This production is characterised by a long production time, with a rotation period of 50 to 150 years for deciduous trees and 40-70 years for conifers. This means that only around 5,000 ha have to be replanted per year. It is not known how much forest is established by natural reproduction or replanting, but we estimate that about 1/5 is established by natural reproduction and the rest by replanting. Pesticides are used particularly on land that is to be replanted and are normally applied 0-2 times in the first five years of the establishment phase. It is common practice to spray with glyphosate before felling so that weed is removed before replanting.

When establishing conifers it is sometimes necessary to take action against the seed pod weevil, which occurs frequently in Central and West Jutland. Other pests that can occur include the nun moth – a butterfly - although control measures are rarely needed for this. Pest problems in the form of insects are extremely rare in deciduous forests.

When establishing deciduous forests it is necessary to use repellents against mice. In areas under heavy pressure from game it is sometimes necessary to treat the top shoots of conifers or to set fences up to prevent biting.

Plan for afforestation

The Danish Parliament’s decision to double Denmark’s forested acreage within one tree generation means establishing 3-4,000 ha of new forest per year. Afforestation offers good possibilities of using mechanical methods of weed control and soil treatment, especially on even areas, while herbicides are used in less accessible areas. There is a particular need for pest control in new areas situated close to earlier forests, where pests have already become established.

7.3 Ornamental greenery

Scope of production

Ornamental greenery comprises Christmas trees and cut greenery. In the past 20 years this production has become of increasing importance to the economy of the entire forestry sector. Denmark is thus a country in which growers have specialised in this production. A substantial part of the production takes place on agricultural land. In the last 10 years exports have varied between 3 and 8 million Christmas trees, most of which are Norman fir. Exports of cut greenery vary between 12,000 and 22,000 tonnes. About 1.5 million Christmas trees and 10,000 tonnes of cut greenery are sold on the home market (Østergaard et al., 1998).

Weed control

In ornamental greenery, weeds are normally controlled with herbicides. It is estimated that herbicides are used on about 70% of the acreage with these cultures, while a combination of mechanical methods and herbicides is used on the remaining 30%. Soil herbicides used to be widely used, but since a large number of these were banned, glyphosate has been used. However, treatment has to be more frequent than in the case of soil herbicides because glyphosate has a smaller long-term effect.

Pest attack

Areas used for production of ornamental greenery are constantly monitored for insect attacks because these can severely affect the quality of the trees. The main pests in this production are common spruce aphid and various species of moth, but severe attacks of seed pod weevil, gall mite and spider mite also occur. Chemical control is of great importance for preservation of the quality of the trees. Norman fir is particularly sensitive to insect attack, whereas abies nobilis needs less protection.

7.4 Conclusion

11% of Denmark is forested. The acreage is expected to increase in the future because of plans for afforestation of 3-4,000 ha per year. Pesticide consumption in forestry accounts for 1% of total agricultural consumption. Most of the consumption is used for weed control in the establishment phase and in the production of ornamental greenery.

Pesticides are used, particularly in the production of Christmas trees, to ensure quality and uniformity, on which sales depend.

References

Linddahl, M. (1996): Socioeconomic consequences of the National Forest and Nature Agency’s proposed pesticide strategy. Report to the National Forest and Nature Agency.

Østergård, K., Hedegaaard, H.M., Søgåaard Jacobsen. J., Christensen, I.H., Nielsen F., Dybkjær T., Rubow, T. (1998): Report on scenarios for phasing out the use of pesticides in private forestry. Report prepared for the Pesticide Committee.