178 MAINE AGRICULTURAL EXPERIMENT STATION. lO,l6. 



It is only fair to state in this connection that this is the first 

 time such a result has been secured in these series of experi- 

 ments since an unsprayed plot has been introduced as a check. 



Arsenate of Lead as a Fungicide;. 



While the conditions for the past season were not such as to 

 make the test of the fungicidal properties of the various sprays 

 in any way a severe one the results obtained with arsenate of 

 lead in controlling apple scab were in general confirmatory of 

 those previously Obtained. Where this material was used 

 alone on plot 5 the amount of scab on the fruit, as compared 

 with the check plot was reduced from 5 per cent to less than 

 half of one per cent. This is the fourth consecutive season in 

 this orchard in which the use of arsenate of lead on experi- 

 mental plots at the rate of 4 pounds of paste or two pounds 

 of the dry powder alone in 50 gallons of water has been fol- 

 lowed by a material reduction of the amount of scab on the 

 crop. One of the striking results obtained from the use of 

 arsenate of lead alone on the Ben Davis, as shown by these 

 experiments, is the relatively small amount of russeting of the 

 fruit. Consequently, as will be seen on reference to the table, 

 the plot sprayed in this way gave the largest percentage of per- 

 fect apples of any in 191 5, or 97.50 per cent. In this connection 

 attention is called to the fact that practically the same record 

 was made on plot 3 which received lime-sulphur 20 per cent 

 stronger than standard dilution combined with one pound of 

 dry arsenate of lead in 50 gallons for the first application, and 

 for the last two sprayings two pounds of riry arsenate of lead 

 alone in 50 gallons of water. 



While the evidence of apple scab control in the field by means 

 of arsenate of lead appears quite conclusive some unpublished 

 results secured by the writer's associate, Mr. M. Shapovalov, 

 indicate that, while it is much retarded, the growth of the apple 

 scab fungus in artificial culture media is by no means prevented 

 when arsenate of lead is added to the culture medium at the 

 same rate at which it was used in water for spraying. Simi- 

 lar results were obtained in germinating the spores of the fun- 

 gus in pure, distilled water and carbonated water in comparison 

 with other spore germination tests where arsenate of lead was 

 added to the same liquids. 



