Effect of Lanolin or Lanolin + Starch Rings on Absorption and Translocation of 2,4-D or Glyphosate in Hemp Dogbane (Apocynum cannabinum)

Lanolin or lanolin + corn ( Zea mays L.) starch rings are often used as barriers on leaves to prevent runoff of foliarly applied 14 C-herbicide treatments. A preliminary experiment showed that 64 and 90% of the applied 2,4-D [(2,4-dichlorophenoxy)acetic acid] and 57 and 87% of the applied glyphosate [ N -(phosphonomethyl)glycine] was adsorbed to or absorbed into a lanolin and lanolin + starch ring, respectively, during 6 days on a glass slide. Absorption and translocation of 2,4-D in hemp dogbane ( Apocynum cannabinum L.) was decreased from 26% down to 16 or 17% of the total applied when a lanolin or lanolin + starch ring was used. Glyphosate absorption and translocation increased with the lanolin ring but not with the lanolin + starch ring. Distribution of the translocated 2,4-D and glyphosate was also altered by use of the ring barriers. Results indicate that one should avoid use of the lanolin ring in 14 C-herbicide absorption studies to simulate field conditions.