Bushy and arboreal weed control with herbicides in Pinus radiata D. Don plantations

Abstract

Bushy and arboreal weed control is a necessity for forestry companies. Plantations are aggressively invaded by ligneous weeds, from either regrowth or seeds, which compete for resources, limiting the availability of water, nutrients, space and light for the plantation. In addition woody weeds obstruct other activities, such as pruning, thinning, transit, harvest, etc. They also infest the stand as monospecies or more commonly as different association of species. Herbicides that suitably control woody weeds are not selective to Pinus radiata D. Don, so they must be applied with "minimum risk techniques". The objective of this task is to increase Pinus radiata plantation yield through an efficient bushy and arboreal weed control, by using efficient and effective application techniques and herbicide mixes.
Four herbicide trial areas were established: 7th Region, Talca (Farm Los Negros), 8 t h Region, Nacimiento (Farm Los Barros), 9 t h Region, Cañete (Farm Elicura) and Lastarria (Farm Los Carrizos), and an operational trial in Nacimiento. Herbicide application techniques were divided into foliage application (foam nozzle Yamaho 25), stump, basal and granule applications. The witness treatments consisted in manual mechanical weeding and no weeding.
Results were observed 150 days after application (DDA). There is no doubt that as time goes by clearer degrees of control as well as weed regrowth capacity are observed. Among the different application techniques, foliage application seems to be the most recommended because of its operational convenience, cost and efficiency. Therefore the most consistent treatment at 150 DDA are: Roundup 7 l/ha + Escort 0.08 kg/ha + adjuvant; Roundup 7 l/ha + Garlon 0.7 l/ha + Tordon 0.7 l/ha + adjuvant and Roundup 7 l/ha + Banvel 1 l/ha + adjuvant.