804 



D. P. Gowing 



Table 1. Some substituted phenyl- and phenoxyalkyl carboxylic acids with hcrbi- 

 cidal properties on young broad-leaf weeds. 



* All except 2,4-D and 3-chlorosalicylic acid (Dow Chemical Co.) and 4-chloro- 

 phenylmercaptoacetic acid (Evans Chemetics, Inc.) synthesized by R. W. Leeper, 

 Pineapple Research Institute, Chemistry Department. 



t Sprays at 100 gallons per acre; chemical dissolved in dimethylformamide and 

 applied with triethanolamine and a wetting agent. 



I Data of M. J. Kent, Pineapple Research Institute, Chemistry Department; 

 1-naphthaleneacetic acid used at 200 p. p.m. as a standard for comparison. 



in loss of the crop, and for this reason such compounds are not used 

 for weed control in pineapple fields. The pineapple plant is forced to 

 flower by the a-propionic and y-butyric analogues of 2,4-D also. How- 

 ever, within the halogen- or alkyl-substituted phenoxyacetic acids, 

 several of the 2,5-substituted and the 3,5-substituted compounds have 

 some herbicidal activity, but all such compounds have thus far failed 

 to force pineapples to flower. Results with some of these compounds 

 and others are shown in Table 1. Pybus et al. (5) have recently re- 

 ported on the effectiveness of certain phenylacetic acids. 



Of these compounds, all have had more or less activity in the split 

 pea-stem test for growth regulator activity with the exception of 3- 

 chlorosalicylic acid and the 3,5-substituted compounds. The latter 

 are herbicidal apparently owing to some contact, or less general sys- 

 temic, activity. Such materials, then, although much less effective 

 than 2,4-D as herbicides, would merit further investigation in crops 

 exceptionally sensitive to 2,4-D since they might be tolerated in drift 

 amounts. Although some of them have the advantages of systemic 

 herbicidal activity, they would be no more injurious to the crop than 

 some nongrowth-rcgulator chemicals in a misdirected contact spray. 



