Cheat Grass

Evaluation of TFMS Herbicidal Activity. The herbicidal potency of the 15 substituted TFMS compounds was rated after a 21-day test period on a 0-100% kill scale. Herbicidal test data were collected for two grass species (Foxtail, Cheat Grass) and a broadleaf weed (Wild Mustard) in the presence and absence of 0.1% (w/v) Tween 80. Since the tests... 

Table VII fists the LD90 values determined for each of the 15 TFMS derivatives in pre-emergence tests on Foxtail, Cheat Grass, and Wild Mustard. The Foxtail and Wild Mustard tests were carried out in the...

Comparisons similar to those outlined in Equations 28-31 were likewise undertaken for the remaining cases (Foxtail with Tween 80 present Wild Mustard with and without Tween 80 present Cheat Grass without Tween 80 present). The statistical parameters for the final best-fit Hansch correlations for each case are listed in Table IX. 

It is evident from the statistical tabulation in Table XI that the TFMS herbicidal data for Foxtail, Cheat Grass, and Wild Mustard are well-correlated by the given Hansch relationships, both in the presence and absence of surfactant. The numbers in parentheses beneath the fit parameter coefficients in Table XI are the standard errors in those coefficients. Perusal of Table XI leads to the following observations ... 

Figure 4a. Three-dimensional perspective plot of the Hansch equation describing pre-emergence activity of 4-substi-tuted TFMS herbicides on Cheat Grass (no Tween 80 present)...

As an illustration of the use of the final Hansch relationships in Table XI in explaining biological activity differences between individual TFMS series members, we will examine the activity of 4-S02CH3-TFMS and 4-C1-TFMS against Foxtail, Wild Mustard, and Cheat Grass. Table XIII gives values of the individual terms in the Hansch equations of Table XI which are appropriate to the action of each herbicide on the three weed types. At a later point, we also examine the activity of 2,4-di-Cl- and 2,4-di-F-TFMS derivatives as predicted by the Hansch relationships in Table XI. 

In general, substituents characterized by large, positive Hammett <7 constants (electron-attracting substituents) exhibit enhanced pre-emergence herbicidal activity on all weed types tested (Foxtail, Cheat Grass,... 

Log a Cheat grass Giant foxtail Wild mustard... 

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