The effect and elimination of the effect of soil settled on jimsonweed’s shoot on clopyralid efficacy

Clopyralid is an important herbicide for controlling the broadleaf weeds in sugar beet fields, but the effect of spray volume and soil settled on the shoot of weeds on its efficacy has not been studied yet. Therefore, a greenhouse study in factorial design (3×2×5) based on completely randomized design was conducted. The first factor included the amount of soil settled on jimsonweed foliage (0, 20 kgha-1 via a dust chamber, and 20 kg ha-1 via muddy rain), the second factor composed of airflow before spraying (0 and 6 kmh-1) and the third factor included spray volume (120, 240, 360, 480, and 600 lha-1). In the absence of soil on the shoot, the highest level of jimsonweed control (> 94%) was obtained with the use of clopyralid at 120 l ha-1. Under the same condition, the efficacy of clopyralid decreased with increasing the spray volume. In the presence of soil on the shoot via both methods, the lowest level of jimsonweed control (25%) was obtained with the use of clopyralid at 120 lha-1. Under the same condition, the efficacy of clopyralid increased with increasing the spray volume. At all spray volumes (except at 120 lha-1), the negative effect of soil settled on the shoot of jimsonweed via muddy rain was greater than dust chamber. Flowing air before spraying was only useful when the source of soil settled on the shoot of jimsonweed was dust chamber. In the presence of soil on the shoot of weed, more spraying volume, but in the absence of soil, low spraying volume is recommended for the use of clopyralid.