Fifty-day-old jimsonweeds (Datura stramonium L.) were susceptible and tomatoes (Lycopersicon esculentum Mill.) tolerant to soil-applied metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] at 0.25 and 0.50 kg/ha. Spray applications of 0.50 kg/ha metribuzin to jimsonweed foliage, or to both foliage and soil, reduced jimsonweed height growth 39 and 66%, respectively; whereas, tomato height was reduced 57 and 50% by the two placement methods, respectively. Metribuzin applied to a basal leaf appeared to move both basipetally and acropetally in jimsonweed, but only basipetally in tomato. Metribuzin applied to tomato leaves reduced growth 28% more when leaves had been abraded than when not abraded. Differential translocation appeared to be a major factor in selectivity. Directed sprays of metribuzin at 0.3 and 0.6 kg/ha on the lower 75% of jimsonweed leaves provided control in the field without injury to tomatoes.

Oat (Avena sativa L. ‘Elgin′) and soybean (Glycine max L. ‘Evans′) were treated with 14C-diclofop-methyl {methyl ester of 2-[4-(2,4-dichlorophenoxy)phenoxy] propionic acid]} or 14C-diclofop alone or in combination with 2,4-D [(2,4-dichlorophenoxy)acetic acid] or bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] and 14C-2,4-D alone or in combination with diclofop-methyl or diclofop. More radioactivity was recovered in the treatment zone after 14C-diclofop-methyl applications, alone or in combination, than after similar 14C-diclofop treatments in oat and soybean. Basipetal movement of radioactivity was 4 and 1% and acropetal movement was 1 and 4% in oat and soybean, respectively, regardless of the diphenyl ether treatment or time. Addition of 2,4-D or bentazon did not reduce translocation of radioactivity from 14C-diclofop-methyl treatments in either plant species. Basipetal movement of radioactivity from 14C-diclofop-methyl was greater than from 14C-diclofop in both oat and soybean. The addition of diclofop-methyl or diclofop did not affect the pattern or amount of 14C-2,4-D radioactivity translocated. In oats, radioactivity appeared to accumulate within the intercalary meristematic region with 14C-2,4-D and 14C-diphenyl-ether applications. Diclofop-methyl at 1 kg/ha applied either to an entire oat plant at the three-leaf stage or the apical meristemic region resulted in plant mortality. The extent to which transport contributes to diclofop-methyl efficacy is questioned.

Studies were conducted in 2006 at Clinton and Kinston, NC, to determine the influence of halosulfuron POST (over the crop plant) or POST-directed (to the crop) on growth and yield of transplanted ‘Precious Petite’ and ‘Tri-X-313’ triploid watermelon. Treatments included a nontreated control, 39 g/ha halosulfuron applied POST-directed to 25% of the plant (distal or proximal region), POST-directed to 50% of the plant (distal or proximal; Precious Petite only), and POST. Watermelon treated with halosulfuron displayed chlorotic leaves, shortened internodes, and increased stem splitting. Vines were longest in the nontreated control (Tri-X-313 = 146 cm, Precious Petite = 206 cm) but were shortest in the POST treatment (Tri-X-313 = 88 cm, Precious Petite = 77 cm). Halosulfuron POST to watermelon caused the greatest injury (Tri-X-313 = 64%, Precious Petite = 67%). Halosulfuron directed to 25 or 50% (distal or proximal) of the plant caused less injury than halosulfuron applied POST. Stem splitting was greatest when halosulfuron was applied to the proximal area of the stem compared with POST-directed distal or POST. Internode shortening was greatest in treatments where halosulfuron was applied to the distal region of the stem. However, Tri-X-313 in the POST-directed 25% distal treatment produced similar total and marketable fruit weight as the nontreated control at Clinton. Fruit number did not differ among treatments for either cultivar. At Kinston, Precious Petite nontreated control and POST-directed 25% distal end treatment had greater marketable fruit weight than the POST-directed 50% proximal and POST treatments. The current halosulfuron registration allows POST application between rows or PRE. Limiting halosulfuron contact to no more than 25% of the watermelon plant will likely improve crop tolerance.