Translocation of 14C-glyphosate [N-(phosphonomethyl) glycine] in johnsongrass [Sorghum halepense (L.) Pers.] was examined in relation to time and illuminance. Plants were treated with 14 C-glyphosate and harvested 3 days and 6 days after treatment. Translocation increased significantly between the 3 day and 6 day harvest. The greatest accumulation of 14 C occurred in areas of meristematic growth. The concentration of 14C recovered in rhizomes nearly doubled between the 3 day and 6 day harvest. Plants harvested after 3 days of treatment in the dark translocated 1.3% of the applied 14C, while plants exposed to full light translocated 4.7%. Plants harvested after 6 days of treatment in the dark translocated 2.1% of the applied 14C, while plants exposed to full light translocated 5.8%. Translocation data indicated that movement of glyphosate in johnsongrass was via the phloem. Accumulation of 14C in roots and rhizomes was significantly greater in plants exposed to full light compared with plants exposed to either darkness or shade.

Simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] was applied annually at 4.5 kg/ha to uncultivated sandy loam of peach (Prunus persica Batsch) for 7 yr (orchard A) and 9 yr (orchard B). Simazine and the metabolite, hydroxysimazine [2-hydroxy-4,6-bis (ethylamino)-s-triazine] as determined by gas chromatography (GC) persisted for 40 and 28 months in soil of orchard A and B, respectively. However, no progressive accumulation of either compound in large quantities occurred from repeated annual applications of simazine to the orchard soils. No metabolites other than hydroxysimazine were detected. Hydroxysimazine was degraded more slowly than simazine and the residue levels of hydroxysimazine were at least 40 times those of simazine 40 months and 28 months after the final application in orchard A and B, respectively. Both simazine and hydroxysimazine residues were detected in the upper 30 cm of the soil profile.

The purpose of the paper is to permit the calculation of prospective costs before starting the biological control of a weed. The cost of the Canadian program from its start in 1950 to the end of 1976 was tabulated in scientist-years by target weed, agent, and the type of study done. This information and international data on the number of agents required to control a weed were used to calculate expected costs. A complete biological control program is likely to cost 18.8–23.7 scientist-years or currently $1.2 to 1.5 million and thus is only economic for use against major weeds. However, it is often possible to capitalize on studies done elsewhere, and under these circumstances biological control may be economic for solving more minor weed problems.