After 10 months, diphenamid residues were found throughout the 0–9 inch soil depth. In silt loam soils under climatic conditions prevailing in and around the bluegrass region of Kentucky, diphenamid residues in soils may be present at phytotoxic levels in the plow layer 10–11 months after application at rates required for weed control in tobacco.

The resistance of corn to the herbicides, 2-chloro-4, 6-bis(ethylamino)-s-triazine [simazine] and 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine), may be related to stalk rot and corn borer resistance. Of five inbred lines of corn studied, three with known resistance to stalk rot and corn borer were found to be much more resistant to simazine and atrazine than were two inbreds which were susceptible to stalk rot and corn borer.

Soil-surface applications of isopropyl N-(3-chlorophenyl)carbamate (CIPC), 2-chloroallyl diethyldithiocarbamate (CDEC), ethyl N,N-di-n-propylthiolcarbamate (EPTC), sodium 2,4-dichlorophenoxyethyl sulfate (sesone), and N-1-naphthylphthalamic acid (NPA) were made on a Willacy fine sandy loam just before and after a 24-to-32 mph windstorm, which moved significant amounts of treated soil. All treatments were overhead-irrigated after the storm. All herbicides performed less efficiently after the wind. CIPC was found below the surface of soil only when applications were undisturbed by the wind.

Absorption and translocation in both leaves and roots is less under low temperatures. Seasonal response of wheat to 2,4-D is conditioned by the stage of growth as well as environment. The response of wheat and downy bromegrass to triazine herbicides is seasonal, whereas the response to carbamate herbicides appears to be influenced by local environmental conditions at time of spraying. Physiological condition of fiddleneck is more important than age, i.e., plants in the rosette stage were always far more sensitive than bolting plants of the same age. Sensitivity to 2,4-D was greater at 26 C than at 10 C or 5 C at all stages of growth. Applications of certain metabolites, especially thiamin, increased the sensitivity of fiddleneck to 2,4-D at low temperatures.

If there was no heavy rainfall or surface irrigation before corn emergence, as ethyl-N,N-di-n-propylthiolcarbamate (EPTC) at 3 lb/A was incorporated deeper into the soil, more corn plants were injured, the height of plants was reduced, and a loss in weight or yield occurred, although the germination of the corn seed was not affected. Implements used to incorporate EPTC did not produce significantly different amounts of corn injury where used at the same depth.

Internal dormancy was shown to occur in western ironweed (Vernonia baldwinni Torr.) and leafy spurge (Euphorbia esula L.) in late summer and fall. Time required for emergence and extent of growth were important indicators of dormancy. Dormancy is apparently broken naturally in the field by low soil temperatures.

A tractor-mounted experimental plot sprayer for applying herbicides is described.

Birdsfoot trefoil, timothy, and sterile pea plants treated with 4-(2,4-dichlorophenoxy) butyric acid [4-(2,4-DB)], formed 2,4-dichlorophenoxyacetic acid (2,4-D) to about the same extent. Apparently the enzymatic ability for beta oxidation can reside in the plant as well as in microorganisms.

Dimethylarsenic acid (cacodylic acid), 2-methoxy-3,6-dichlorobenzoic acid (dicamba), 2,6-dinitro-N,N-di-n-propyl-alpha-alpha-alpha-trifluoro-p-toluidine (trifluralin), and O-(2-4-dichlorophenyl) O-methyl isopropyl-phosphoramidothioate (DMPA) were tested to determine if they could selectively control nimblewill (Muhlenbergia schreberi J. F. Gmel.) in Kentucky bluegrass (Poa pratensis L.) pasture. DMPA reduced the nimblewill population 95% during the initial year of treament, while other herbicides gave only 61 to 72% reduction. No effect on nimblewill was evident the second year after application. None of the herbicides caused severe or permanent injury to the bluegrass.

In a closed system the vapors from the potassium salt of 4-amino-3,5,6-trichloropicolinic acid caused severe damage and death of Pinto beans. Vapors from the potassium salt of 4-amino-3,5,6-trichloropicolinic acid caused more injury to Pinto beans than vapors from the same application rates of the propylene glycol butyl ether esters of 2,4-dichlorophenoxyacetic acid or the dimethylamine salt of 2-methoxy-3,6-dichlorobenzoic acid.

Thirteen treatments during a 5-year period with a 1 : 1 mixture of the propylene glycol butyl ether esters of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-5 trichlorophenoxyacetic acid (2,4,5-T) were required to eradicate an established stand of kudzu, Pueraria lobata (Willd.) Ohwi.

Black henbane (Hyoscyamus niger L.) has invaded cultivated land, pastures, and disturbed areas in east central Saskatchewan. This species flourishes during cycles of abundant moisture and disappears during dry cycles, surviving in Saskatchewan only in moist depressions or disturbed areas. Summerfallow, fall tillage, and competition from vigorous perennial grasses provide effective control of the weed. Black henbane is not likely to become a serious deterrent to crop production in Saskatchewan.

Catalase and peroxidase activities were run at several ages on two lines of corn (Zea mays L.)—GT112 RfRf, resistant, and GT112, susceptible to 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine). Atrazine significantly decreased catalase activity in GT112, while in treated GT112 RfRf catalase activity was usually significantly increased. Catalase activity was higher in GT112 RfRf than in GT112 for both treatments at all ages. GT112 RfRf had a higher peroxidase activity than GT112 when both were untreated, but when treated with atrazine there was no overall trend.