4 CIRCULAR 411, U. S. DEPARTMENT OF AGRICULTURE 



At the beginning of this study it was realized that the growth habit 

 of cabbage heads (i. e., from within, accompanied by the progressive 

 loosening of some of the outer leaves) is an important factor in deter- 

 mining when the application of poisonous insecticides should be dis- 

 continued in order that the harvested product may not contain an 

 excess of harmful residue. Hence 25 plants in each experiment were 

 marked at the time the last application of dust was made, by cutting 

 a V-shaped notch in the youngest exposed leaf and recording the 

 position of the marked leaf at the time of sampling. 



The data obtained from these notching tests demonstrate that 

 Copenhagen Market cabbage grown at Baton Rouge and marketed 

 as U. S. grade No. 1 may include, late in the fall, some of the leaves 

 that become visible 30 clays before maturity, and, in the spring, 

 under favorable growing conditions, some of the leaves that become 

 visible 10 to 15 days before maturity. The corresponding periods of 

 time for the Charleston Wakefield variety grown at Charleston were 

 longer and ranged from 20 to 40 days, depending upon the character 

 of the season. 



RESULTS 



The pertinent data obtained in experiment 1 at Charleston are 

 given in table 2. 



Table 2. — Arsenic residue l on the loose leaves, stripped heads, and entire plants of 

 20-plant samples of Charleston Wakefield cabbage that were dusted with paris 

 green and lime (1 to 10) and lead arsenate and lime (1 to 5), experiment 1, Charles- 

 ton, S. C. 



From last dusting to sampling 



Total 

 appli- 

 ca- 



Paris 



green and lime, 1 to 10 



Lead arsenate and lime, 



1 to 5 











Residue AS2O3 per 





Residue AS2O3 per 





Dura- 

 tion of 

 period 





Average 



pound plant material 



Average 



pound plant material 



Period 



Rain- 

 fall 



tions 



appli- 

 cations 





appli- 

 cations 



















per acre 



Loose 



Stripped 



Whole 



oer acre 



Loose 



Stripped 



Whole 













leaves 



head 



plant 





leaves 



head 



plant 





Days 



Inches 



Nu ru- 

 ber 



Pounds 



Grain 



Grain 



Grain 



Pounds 



Grain 



Grain 



Grain 



Dec.5-Dec.15__ 



10 



0.44 



7 



20.4 



1.260 



0.028 



0. 3694 



25.5 



0.560 



0.033 



0. 2274 



Nov. 25-Dec. 15. 



20 



.95 



6 



19.6 



.322 



.011 



.1101 



25.4 



.307 



.009 



.1073 



Nov.lo-Dec. 15. 



30 



1.89 







19.4 



.175 



.005 



. 0572 



25.5 



.100 



.003 



.0432 



Xov. 5-Dec.l5_. 



40 



2.82 



4 



16.5 



.056 



.002 



.0202 



24.0 



.145 



.003 



.0461 



Oct. 25-Dec. 15- 



51 



4.99 



3 



16.5 



.012 



.004 



.0074 



24.0 



.013 



.002 



.0057 



Oct. 14-Dec. 15- 



62 



7.30 



2 



16.5 



.016 



.002 



.0067 



24.0 



.007 



.003 



.0042 



0ct.5-Dec. 15. .. 



71 



8.50 



1 



16.5 



.006 



.001 



.0026 



24.0 



.020 



.005 



.0096 



1 Treatments leaving a residue exceeding the legal tolerance of 0.01 grain of arsenic trioxide per pound 

 of marketable product are shown in bold-faced type. 



These data show that a large portion of the arsenic residue on 

 cabbage treated with paris green or lead arsenate is found on the 

 loose leaves. The legal tolerance of 0.01 grain of arsenic trioxide 

 per poimd was exceeded on the entire plant when dusted four times, 

 the last application being made 40 days before harvest, under weather 

 conditions which included 2.82 inches of rainfall. It was exceeded 

 on the stripped heads, in the instance of paris green, when the last of 

 six applications was made 20 days before harvest and the precipita- 

 tion for the period totaled 0.95 inch. 



