42a EXPERIMENT STATION. [Jan. 



seemed to make it particularly worth testing, these substances 

 being at the time so costly because of war conditions. It 

 proved to be a very slow poison even when larvae had eaten 

 very freely of sprayed leaves, requiring about twice as long 

 to become effective as a standard arsenate of lead. On the 

 other hand, it appeared to be slightly repellent to young 

 larvfe. When applied at the minimum strength recommended 

 by the manufacturers, leaf injury, even on mature leaves, 

 always followed; when applied at an increased strength to 

 obtain killing efficiency equal to that of a standard spray, 

 the burning became so serious that its use was out of the 

 ciuestion. 



The scarcity of nicotine sulfate (fiorty per cent) in some 

 parts of the State during the time when the potato aphis was 

 abundant led to the use of many substances as substitutes. 

 Among these was sulpho-napthol (now spelled Sylpho-Nathol), 

 which was frequently used and sometimes highly recommended. 

 To ascertain whether this material had any real value for 

 this purpose a series of tests was made, both in the laboratory 

 and in the garden. The results indicate that, to be of any 

 value against plant lice, Sylpho-Nathol must be used as strong 

 as 13^ fluid ounces per gallon of water. At this strength, 

 however, burning of the leaves always occurred, and though 

 the plants often recovered and made new growth, the check 

 they suffered was as great as would have been produced by 

 the plant lice unless these were unusually abundant. 



Plant Lice Killer, manufactured by the Sterling Chemical 

 Company, was also tested to some extent, though not available 

 until rather late in the season for complete data, the object 

 being to determine the best dilution for aphid control and its 

 value for this purpose. Considerable difficulty was met with 

 in preparing the material for use, owing to its oily nature, 

 and, when prepared, constant agitation was necessary to 

 keep it from separating out of the mixture. It was found, 

 however, when properly mixed and maintained, to be a very 

 effective material for use with aphids, — proportions of 1 

 to 15 and 1 to 20 of water killing practically all the insects 

 reached, and 1 to 30 killing about 90 per cent of them. On 

 foliage, the strength of 1 to 15 injured only the most tender 



