CHEMICAL CONTROL OF WEEDS IN NEWLY PLANTED SHELTERBELTS

Abstract

A number of herbicides were tested to find residual and contact-type herbicidal treatments for the 1st year or 2 of new shelterbelt plantings on different soil types using caragana (Caragana arborescens Lam.) as the test species. The herbicides, tested individually or in combination, were amitrole, chloramben, chloroxuron, chlorthal, dichlobenil, dinoseb, diuron, linuron, norea, paraquat, simazine, swep, and trifluralin. A number of herbicidal treatments were effective in controlling weeds without tree injury during the initial years of a new shelterbelt planting. These include herbicides that can be applied as directed treatments (e.g., amitrole (8–10 kg/ha) and paraquat (1–2 kg/ha)); pre-planting incorporated treatment (e.g., trifluralin (2–4 kg/ha)); and soil surface treatments as pre-emergence to weeds (e.g., chloramben (5 kg/ha), dichlobenil (4–6 kg/ha), diuron (2–4 kg/ha), or linuron (2–4 kg/ha)). All of these treatments gave satisfactory weed control at one rate or another and in different soil types. All of these herbicides are considered less residual than simazine and therefore should not carry over residues to damage the replacements. None of these treatments was antagonistic to weed control or crop tolerance with simazine as a follow-up application once the new planting was established. Yearly applications of simazine (2–4 kg/ha), both as initial and follow-up treatments, to new plantings of caragana were also very effective, provided that the appropriate rates were used and replacements were not necessary.