A Review of Non-Chemical Weed Control Practices in Christmas Tree Production

Abstract

Weeds interfere with Christmas tree growth at any time and at any stage of production. Growers mostly rely on mechanical mowing and applications of herbicides for weed control in their fields. However, herbicides can be phytotoxic to non-target plants, can cause environment-related issues, and their repeated application can even cause herbicide-resistant weeds. The main objective of this manuscript is to provide a review of non-chemical weed control strategies in Christmas tree production and identify areas where current practices could potentially be improved or in which further research is required. Preventing the introduction of weed seeds requires controlling weeds along farm roads, maintaining clean equipment, and eliminating new weeds before they start seeding. Mowing helps to reduce the number of seeds produced by the weeds and can significantly reduce competition with trees. Shropshire sheep are well suited for grazing Christmas tree plantations as they prefer grazing on grasses and weeds rather than on coniferous trees. Weeds can also be controlled around Christmas trees by mulching. Organic mulch can improve soil moisture, maintain soil temperatures, enhance root establishment and transplant survival, and improve plant establishment and overall growth. Incorporating cover crops into Christmas tree plantations may improve tree growth, quality, and soil fertility and can supplement conventional nitrogen fertilizers. However, if cover crops are not properly managed, they can be highly competitive with the trees. Flaming can cause suppression of many annual weed species but is less effective on larger weeds and needs to be applied with caution. Several insects have been used as biological agents to control selective weed species. However, further research is required to focus on several potential biological agents, different types and depths of mulches, on cover crops types and their competition with different species of Christmas trees and their effects on seedling survival and growth.

Phytodiversity in Christmas‐tree plantations under different management regimes

“…As soils in the study area do not contain lime, the higher carbon In conventional CTP, vegetation management is the most important factor influencing vegetation structure and species communities (Streitberger and Fartmann, 2020). For promoting the desired growth of Christmas trees, a vegetation-free environment is favoured by the farmers, as high herb and grass cover reduces tree survival and quality (Saebø et al, 2009;Saha et al, 2020). Therefore, vegetation management is intensively pursued within conventional CTP, resulting in a high proportion of bare ground and stones/gravel (this study; see also Streitberger and Fartmann, 2020).…”

“…Until now, knowledge on the effects of these vegetation management methods on phytodiversity is limited (cf. Saha et al, 2020). Next to reduced chemical input, alternative measures for vegetation management may be associated with other positive ecological side-effects.…”

“…Next to reduced chemical input, alternative measures for vegetation management may be associated with other positive ecological side-effects. For example, the application of organic mulch can increase soil moisture-for example by reduced evapotranspiration and increased percolation and retention-and increases soil nutrients by its decay (Saha et al, 2020).…”

“…Nonetheless, non-chemical vegetation management, such as grazing or mulching, is labour-intensive (Saha et al, 2020) and hardly applicable within large-scale cultivation. Herbicide treatment is, therefore, still the most feasible method for vegetation management within large-scale plantations.…”

“…They compared vegetation composition of conventional CTP with other land‐use types such as intensively managed non‐native spruce ( Picea abies [L.] Karsten) forests. Vegetation management in CTP is essential for the farmers to avoid negative effects of competition by plants on tree survival and quality (Saha et al, 2020). As a consequence of chemical vegetation management, conventional CTP are characterised by a unique plant species community composed of ruderal species and an intermediate species diversity compared to other habitat types, such as spruce forests or improved grasslands (Streitberger and Fartmann, 2020).…”