60 On the Disease of Rust. 



sive heat, if the air be dry, generate it. But should 

 touch rain be followed by that state of air which we call 

 close, sultry, and damp, and which we find so remarkably 

 oppressive to our feelings, the rust is almost certain to 

 strike (as the formers term it) the wheat. Nor is it ne- 

 cessary that much rain should precede the disease : on 

 the contrary; heavy fogs, or very copious dews, accom- 

 panied, or immediately succeeded (while the wheat is wet) 

 by great heat and a calm state of the air, more frequently 

 generate rust than immoderate rains. 



Such a state of the air more commonly prevails on 

 the margins of rivers, marshes, swamps, mill-ponds, very 

 flat or bottom-lands, than elsewhere ; and it is lands thus 

 situated that are most subject to the disease of rust. 



In the southern parts of Virginia, where the heat is 

 frequently very great, even as early as the middle and 

 latter end of May, the rust sometimes destroys the 

 wheat in the boot (as we term it) ; that is, before the 

 heads have fully put out : but more frequently it occurs 

 when the heads are completely formed, and in blossom, 

 or in the milky state. On this side of the Ridge*, I 

 have never known it strike the wheat earlier than the 

 middle of June : more commonly from the 20th to the 

 tatter end of the month. In the latter case, injury is 

 not materially done, except to very late wheat, or such 

 as had not the grain completely formed. At this period, 

 if the rust be violent, we find particular spots, in our' 

 best and most forward fields, injured. These spots are 



* The Blue Ridge, or South-Mountain. 



