64 MASS. EXPERIMENT STATION BULLETIN 202. 



temperature was kept between 60° F. and 70° F. Spores from these 

 sulfured plants were tested from time to time and were uniformly unable 

 to germinate. The mycelium in the plant remained alive, and occasion- 

 ally produced new sori near the old ones. But new infections were 

 impossible, and the spread of the disease was checked. In one case 

 some young plants which had been sulfured became infected, but the 

 explanation was soon found. They had been grown since sulfuring 

 at a temperature not over 50° F. To be successful, the sulfur must be 

 accompanied by some rise of temperature. 



Fungine, a potassium polysulfide preparation, is toxic to the uredinio- 

 spores of P. Antirrhini. It controls snapdragon rust under glass if applied 

 to the plant frequently, but its use is not recommended, for it has no 

 advantages over powdered sulfur, while it costs more and cannot be 

 applied as thoroughly as a dust. 



Summary of Control Measures. 

 Many of the experiments already described contain suggestions as to 

 the control of snapdragon rust. They may be summed up as follows : — 



1. There is only very slight chance of rust entering a house on the 

 seeds. The urediniospores would not live on the seeds. Teliospores 

 are not formed till after seed is harvested, and are of no use to the fungus 

 when formed. 



2. A house which has contained snapdragon rust should not be used 

 for snapdragons the following year if any plants have remained alive 

 during the interim, nor unless the house has been dried out. 



3. Cuttings should not be taken from a bench showing rust. If such 

 cuttings must be used, dust them with powdered sulfur, and give them 

 a high temperature for a few nights. 



4. Varieties showing resistance to rust should be selected. The list 

 of varieties showing relative susceptibility should be of assistance here. 



5. Water should be kept off snapdragon foliage. In watering, only 

 the soil should be wet. If syringing becomes necessary it should be done 

 on a sunny morning so that the foliage will dry off quickly. 



6. Insects should be kept down; they serve to spread the rust. But 

 cyanide must be used carefully, as snapdragons are easily injured by it. 



7. If rust appears the plants should be dusted with finely powdered 

 sulfur. If only a few isolated leaves are infected they should be removed 

 by hand picking. The sulfur should be applied with a good bellows 

 that will throw clouds of dust. The temperature should be kept up for 

 a few nights. (For more detail on sulfuring, see the article by Dr. 0. 

 R. Butler, 1917.) 



8. A solution of cuprammonium sulfate containing 0.065 per cent 

 copper will control the fungus, but because of its toxic effect on the 

 foliage it can be used with safety only when the sprayed foliage will dry 

 within one hour. 



9. Bordeaux mixture is absolutely ineffective. 



