Efficacy and selectivity of pre-emergent sunflower herbicides under different soil moisture conditions

Abstract

We ranked the most frequently used pre-emergent herbicides in sunflower (Helianthus annuus) according to their efficacy and selectivity under different soil moisture conditions within 2008–2011. The efficacy of oxyfluorfen, aclonifen, acetochlor, dimethenamid, and propisochlor on the majority of weeds (Chenopodium album, Echinochloa crus-galli, Amaranthus retroflexus, Mercurialis annua, and Solanum physalifolium) was only slightly affected by the soil moisture and these herbicides can be used in arid and semiarid regions. The efficacy of linuron, prosulfocarb, and pethoxamid was strongly affected by soil moisture and was insufficient under dry conditions. The majority of herbicides showed good selectivity for sunflower. Crop injury rate of 5–15% was recorded after application of flurochloridone and acetochlor. For flurochloridone, the phytotoxicity increased due to irrigation after herbicide application. The highest sunflower injury rate (27–35%) was recorded after application of oxyfluorfen.