134 PCNGI AND FUNGICIDES 



This mildew is closely related to the Downy Mildew 

 causing potato rot, to which it is similar in life-history 

 and habits. The mycelium develoj^s in the tissues of 

 the bean plant, and usually sends out its fruiting 

 branches through the breathing pores (or stomata). 

 The small oval summer spores tire produced upon the 

 tips of these branches, as seen in Fig. 56, h. These 

 spores generally germinate by means of the so-called zoo- 

 spores, (a), in a way precisely similar to the germination 

 of the potato fungus spores described on Page 8. No 

 winter stage of the fungus is yet known. 



Treatment. — All leaves, stems and other refuse 

 from the bean plants should be burned as soon after har- 

 vest as possible. Experiments in spraying with fungi- 

 cides have apparently not yet been tried, but the success 

 attending spraying for the related fungus on potatoes 

 indicates that good results are likely to be obtained in 

 this way. The ammoniacal copper carbonate would be 

 a good fungicide for the purpose. 



Literature. — The most important account of this 

 disease is that published by Dr. Thaxter in the report of 

 the Connecticut Experiment Station for 1889 (pp. 

 167-171). 



