IXSECT PESTS AND DISEASES 129 



methods of attack, it is not greatly feared. It is not, 

 however, a thing to be tolerated and remedial measures 

 should always be put in force upon its appearance. This 

 disease first appeared in England in 1895, in the fol- 

 lowing year it appeared in Massachusetts, and during 

 the next few years hardly a collection existed in which 

 it was not present. 



The plant pathologists, however, came to the 

 rescue, explained its nature, suggested methods of 

 combat and ways to avoid attack, and, forearmed with 

 knowledge, we need no longer be seriously alarmed 

 should an outbreak suddenly appear. There are two 

 periods of the year when rust, if present, breaks out 

 in virulent form. One of these times is during August 

 or early September. Conditions that favor attack are 

 weak or overcrowded plants, with insufficient ventila- 

 tion and excessive moisture, especially at night. Strong 

 plants are resistant, and if spraying is performed early 

 so that the leaves dry by night, this also is helpful. It 

 also, appears in spring about the time of propagating 

 young stock, this attack, in all probability, resulting 

 from spores that fell from the old plants the previous 

 summer, found lodgment in the soil and conditions 

 congenial to renewed energy when the plants com- 

 menced their spring growth. 



When an attack appears no time should be lost 

 in applying remedial measures. If only a few leaves 

 are infected they may be picked off and burned. The 

 plants should then be sprayed with some antidote, of 

 which there are several, but possibly none more effectual 

 than sulphide of potassium or liver of sulphur. It 

 is a hard stonelike substance easily obtainable from 

 any large wholesale drug store. It dissolves readily 

 in cold water and may be used with perfect safety in 

 the proportion of one ounce dissolved in two gallons 



