482 



CHEMICAL AGENTS 



0.1 1.0 10 100 300 



Concentration, mM per liter 



Figure 11. The effect of the concentration of tetramethylthinram disulfide (TMTD) 

 on spore germination of Stemphylium sarcinaeforme. Redrawn from Dimond, 

 Horsfall, Heuberger, and Stoddard (91), by permission of the Connecticut Agri- 

 cultural Experiment Station, New Haven, Connecticut. 



plained in a similar way. Figure 1 1 illustrates the well-known bimodal 

 dose-response curve characteristic of this family of toxicants; the gen- 

 eral form of the curve shown has been confirmed in studies on spore 

 germination of Venturia inaequalis (298) and on growth of Aspergillus 

 niger (196, 198). 



The structures of interest are shown in Figure 12, with code abbrevi- 

 ations. Other complexes can, of course, be prepared and have been 



CH 3 n n CHo 



N — C— S— S— C— N 

 CH3 CH3 



Tetramethylthiuram disulfide (TMTD) 



CrL 



N— C— S— Na 



Sodium dimethyldithiocarbamate 

 (Na DMDT) 



CH. 



\ 



ch/ 



N— C— S— Fe. 



S— C— N. 



S— C— N 



/ 



.CH 3 



CH 3 

 CH 3 



/ 



\ 



CH, 



S ~ 13 



Ferric dimethyldithiocarbamate (Fe DMDT) 

 Figure 12, The structure of some dithiocarbamate fungicides. 



