Adjuvant enhancement of large crabgrass (Digitaria sanguinalis) control with dithiopyr

Steven J. Keeley, Bruce E. Branham, Donald Penner

Research output: Contribution to journalArticlepeer-review


A greenhouse study was conducted to determine the effectiveness of adjuvants on postemergence large crabgrass control with dithiopyr. Using barriers to isolate foliage or soil, the primary site of dithiopyr uptake was found to be via foliage. Laboratory and greenhouse studies elucidated the factors involved in enhancement of crabgrass control by dithiopyr with nine superior adjuvants. Two adjuvants increased dithiopyr absorption by 3.7 to 4.3% over the herbicide alone. However, none of the adjuvants increased dithiopyr translocation out of the treated leaf. Treatment of a single large crabgrass leaf indicated that enhancement of dithiopyr activity by adjuvants involved an effect on translocation, on spray retention, and on the external movement of the spray solution to the apical meristem, with the relative importance of any I factor depending on the particular adjuvant used. Because of the large losses of dithiopyr during absorption/translocation studies, a separate volatilization experiment determined that 70% of the applied dithiopyr volatilized within 24 h at 24 C. Dithiopyr absorption decreased and volatilization increased with each 10 C increase in temperature. Nonrecoverable dithiopyr ranged from 46 to 55% at 5 C to 92 to 95% at 35 C. Volatility losses of this magnitude may mitigate adjuvant enhancement of postemergence grass activity of dithiopyr.

Original languageEnglish (US)
Pages (from-to)205-211
Number of pages7
JournalWeed Science
Issue number2
StatePublished - 1997


  • Site of uptake
  • surfactants
  • volatility

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science


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