The Four-lined Leaf-Bug. 243 



This year the emulsion was tried on the nymphs when about one- 

 half grown. When the emulsion was diluted with ten parts of water 

 it had but little effect. But when only five parts of water were used, 

 and the sjjraying was thorough, the nymphs died in a minute or two. 



Prof. Cook reports as follows in regard to the use of kerosene 

 emulsion against the pest in Michigan in 1891: " We sprayed these 

 striped currant bugs on the bushes and in the laboratory with kerosene 

 emulsion made with both hard and soft soap and with pyrethro- 

 kerosene emulsion.* There were almost too few bugs on the currant 

 bushes to make the experiments satisfactory, but in the field and in the 

 laboratory both applications killed the insects, and the bushes in the 

 garden were freed of the blighting bugs." 



We have tried no experiments in the field with the emulsion. Our 

 experiments in the insectary as recorded above indicated that the emul- 

 sion must be thoroughly applied and must contain at least nine per 

 cent of kerosene (that is, the Riley-Hubbard emulsion diluted with six 

 or seven parts of water) to be effectual against the nymphs, and con- 

 siderably stronger, diluted not more than five times, to affect the adults. 



Prof. Cook's experiments both in the field and the laboratory are, 

 however, quite conclusive and indicate that the emulsion affords a 

 practicable method of combating the pest. As Prof. Cook does 

 not mention the early stages of the insect, it is probable his experi- 

 ments were made on the adults . 



The best and most effectual time to apply the emulsion will be 

 before the insect has reached the adult stage, that is, while they are 

 still nymphs. As the adults begin to appear the first week in June, 

 the spraying should be done the last week in May or as soon as the 

 bright vermilion red nymphs are seen on the bushes. With the insect 

 thus destroyed in its nymphal stage, the buds of dahlia, rose, and the 

 leaves of other herbaceous plants would not suffer from the attacks of 

 the pest if, as the records indicate, the adults alone are responsible for 

 this injury. The insect in all of its stages is so very active that the 

 spraying must be very thorough to be effectual . 



* Professor Cook's emulsions contain one quart of soft or one pound of hard 

 soap dissolved in two qua i ts of hot water and one pint of kerosene added. 

 This is diluted with an equal amount of water when it is ready for use. This 

 gives nearly seven per cent of kerosene in the dilution as applied ; or about the 

 same amount of kerosene that the Riley-Hubbard emulsion has when diluted 

 with nine parts of water, '"^he excess of soap in Cook's emulsions may increase 

 their insecticidal value af used against the Four-lined Leaf-bug. In the 

 pyrethro-kerosene emulsion one gallon of kerosene is filtered through two 

 pounds and a half of pyrethrum powder, and the filtrate is used in the same 

 manner as kerosene in making the emulsion. 



