October, '22] de ong: hard waters and sprays 339 



and the presence of husk leaves as characters associated with the amount 

 of injury due to the earworm. 



The practical application of physiological and morphological studies 

 offers certain possibilities worthy of further investigations. The writer 

 is of the opinion that such studies, carried on in co-operation with the 

 agronomist, the plant breeder and the chemist, open the way for certain 

 intensive investigations which ultimately will prove valuable in the 

 development of control measures. Many of the characters associated 

 with earworm activities can be changed or modified by careful breeding, 

 and varietal studies of com may reveal certain strains lacking in some of 

 the characters attractive to the moths. 



THE RELATION OF HARD AND ALKALINE WATERS TO 



THE PREPARATION AND DILUTION 



OF SPRAYS AND DIPS 



By E. R. de Ong, University of California 



The insecticidal ingredients of sprays and dips have been studied 

 sufficiently so their properties are now beginning to be understood, but 

 the water used as a dilutant and carrier for them has received almost 

 no attention from the entomologist or the insecticidal chemist. And 

 yet the composition of the water varies widely according to locality, 

 and from season to season, in the same vicinity. In the Santa Clara 

 Valley, California, where this study was made, a range in variation 

 of 2300 per cent was found, while the hardness in the tap water from 

 one water supply company increased 11 per cent from the first of 

 May until the middle of August. The latter change may have been 

 due entirely to a seasonal variation or to a shifting of the source of 

 supply. This instance will serve, however, to show that the analysis 

 of water from a supply company may vary materially during the year. 

 Complete yearly records have not been kept but we would natur- 

 ally expect that concentration of salts in underground water sup- 

 plies or surface streams would increase during a long continued arid 

 season, such as is common in California. 



The soluble salts in water are now recognized as a source of danger 

 in two ways, in the preparation or dilution of sprays and dips : — (1) by 

 chemical reactions with the insecticidal or fungicidal materials, which 

 neutralize their efficiency or form dangerous compounds. For example, 

 the use of alkaline or saline waters with acid (standard) arsenate of 



