SECTION IX. — THEORIES OF DAMAGK AND GENERAL PROBLEMS. 127 



The known facts on the effect of moisture on blight can be 

 summarised as follows : — 



(a) Extreme dryness such as that experienced in unusually dry 



dry-seasons, or in fields from which the standing canes have 

 been removed early, or where the soil is in poor physical 

 condition so that percolation from beneath does not take 

 place freely, is followed by an increased amount of blight. 



(b) Medium dryness, such as that in dry-seasons which are not 



severe, and particularly in fields where the canes are standing, 

 or the soil is in good physical condition, or where unusual 

 percolation takes place {e.g. Hermitage pond) reduces amount 

 of blight. 



{e) Slight dryness during wet season, as at the Indian Summer, 

 increases the amo'unt of blight. 



(d) Normal regular moisture of wet season, reduces the amount 



of blight. 



(e) Extreme moisture in wet season especially on heavy soils, 



increases the amount of blight. 



These facts appear at first to be extremely contradictory, but an 

 -examination of Table VII showing the known effect of different grades 

 of moisture on the froghopper itself and on its parasites, on root disease 

 and on cane, will provide, I think, a reasonable explanation of these 

 observed results. 



