Effects of Herbicides Applied Preplant or Preemergence on Weeds and Sunflowers
1972
Johnson, B. J.
Herbicides applied preplant or preemergence were evaluated on weeds and sunflowers (Helianthus annuus L.) over a 3-year period at Experiment, Georgia. Alachlor (2-chloro-2',6'-diethyl-N-(methoxymethyl) acetanilide) applied in combination with either chlorpropham (isopropyl m-chlorocarbanilate) or prometryne (2,4-bis(isopropylamino)- 6-(methylthio)-s-triazine) were the only herbicide treatments that satisfactorily controlled both grasses and broadleaf weeds in sunflowers planted in April and June from 1969 through 1971. A higher percentage of broad leafweeds was controlled with herbicides applied preemergence to sunflowers planted in April than when applied to sunflowers planted in June. Sunflower plants were severely injured from incorporated treatment of nitralin (4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline) in 1 year and from incorporated or injected treatments of EPTC (S-ethyl dipropylthiocarbamate) in 2 years. Herbicides applied preemergence to sunflowers planted in April did not affect achene yields when compared with the untreated check, whereas, alachlor applied alone or in combination with chlorpropham or prometryne to sunflowers planted in June produced higher yields than did the untreated check. None of the herbicide treatments caused sunflowers to have a higher achene oil content than did untreated sunflowers.
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