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Synopsis Variety ✕ environment first order interactions were small and nonsignificant for most traits studied. But the interaction of variety ✕ location ✕ year was highly significant although small in relation to the variety component for most of the characters. From a comparison of theoretical variances of treatment means with varying plot allocations, adequate information on the relative performance of tobacco varieties in North Carolina can be estimated from data obtained in 2 years, at each of 5 locations with 3 replications.

Imazaquin {2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid} was evaluated in the field for weed control in flue-cured tobacco (Nicotiana tabacumL.) during 1983 and 1984. The 75 DG formulation of imazaquin was used at 0.28 and 0.42 kg ai/ha. Methods of application were: preplant incorporated, over the top immediately after transplanting, postbed incorporated, and early postemergence. Imazaquin controlled 90%, or better, of common lambsquarters (Chenopodium albumL. # CHEAL), common ragweed (Ambrosia artemisiifoliaL. # AMBEL), redroot pigweed (Amaranthus retroflexusL. # AMARE), spiny amaranth (Amaranthus spinosusL. # AMASP), ivyleaf morningglory [Ipomoea hederacea(L.) Jacq. # IPOHE], sicklepod (Cassia obtusifoliaL. # CASOB), and prickly sida (Sida spinosaL. # SIDSP) with all application methods except early postemergence. It controlled 80 to 89% of large crabgrass (Digitaria sanguinalisL. # DIGSA) by the soil-applied methods. Postemergence applications of imazaquin controlled common ragweed, pigweed spp., ivyleaf morningglory, prickly sida, and sicklepod. Imazaquin was less effective postemergence on lambsquarters and large crabgrass. Tobacco tolerated use of imazaquin by all methods of application except preplant incorporation.

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Absorption of14C-imazaquin by leaves of field-grown flue-cured tobacco was similar when applied to young seedlings immediately after transplanting or to plants 3 wk after transplanting. The distribution of14C in treated leaves indicated that 40% was absorbed, 54% remained in water extracts of leaf surfaces, and 6% was found in the epicuticular wax layer 8 d after treatment. Translocation of the herbicide from treated leaves to roots was very low (4 to 5%). In contrast, soil applications of imazaquin and subsequent uptake by roots resulted in retention of 40 to 53% in roots and translocation of 47 to 60% to shoots after 8 d. Analyses of methanol-soluble extracts of14C indicated that more than 77% of the foliar-applied herbicide was metabolized in roots and upper shoots after 2 d. Similarly, 64% or more of the imazaquin was degraded in roots and shoots 2 d after root absorption.