USE OF KEROSENE EMULSIONS AGAINST THE WORMS. 159 



hardly felt. Moreover, Professor Comstock's *' emulsion" may liave been less perfect 

 than that used by ourselves. The kerosene water was applied in the following exper- 

 iments by means of a hand-atomizer, because from former experience I I'elt convinced 

 that the oil can successfully be applied only in the form of the finest spray. Refined 

 kerosene was used, instead of crude coal oil, because the former was more readily 

 procured at Selma than the latter. From my experience with the crude coal oil in 

 1879, 1 am inclined to think that there is not much difference between the two, either 

 in regard to insecticide property or to their injurious effect on the plant. The chief 

 difficulty to overcome in the application of kerosene being the susceptibility of the 

 plant, a series of experiments was first carried on to ascertain the proportion of the 

 oil that could be applied without harm to the plant. This was in the first part of 

 September, when but very few worms were at hand. 



The emulsion was first diluted with five times that amount of water, thus giving 1 

 part of the oil to 19 parts of milk and water ; thea with ten times that amount nf 

 water, and then used in still weaker dilutions. That the stronger mixture considera- 

 bly scorched the plant was to be expected, but I would mention in this connection 

 that a mixture of 1 part of kerosene to about 25 parts of water, which was incident- 

 ally applied to a few corn-stalks and cow peas, did not seem to injure those plants. 

 The limit where the spray is less injurious to the plant begins with a mixture of about 

 l,part of oil to 120 parts of water, but I cannot give in exact figures the mixture that 

 can safely be applied to the plant, as much depends on the amount of the fluid actually 

 applied. With a small hand-atomizer the leaves nearest at hand receive a much larger 

 amount of the fluid than those farther off, the force of the spray which strikes fullest 

 the nearest leaves undoubtedly increasing the influence of the oil. A mixture of 1 

 part of the oil to 160 parts of milk and water, when moderately applied, is not injuri- 

 ous to the leaves. In these and the above-given figures I have not included the excess 

 of the oil which floats on the surface of the mixture, and which I took care not to ap- 

 ply to the plant. How much this excess is in proportion to the amount of oil used in 

 preparing the emulsion I had no means to determine, but the amount of oil actually 

 applied to the plants is at any rata smaller than the figures given above. Old leaves 

 and bolls are the least liable to be injured by the kerosene spray ; very young shoots 

 and squares somewhat more so, while young leaves fully developed and blossoms are 

 most readily affected. In bright, hot weather the efiect of the oil on the plant is visi- 

 ble in a few hours, dry and crisp spots appearing on the leaves, and extending more 

 and more, according to the amount of strength of the kerosene mixture. In cloudy 

 weather the effects are less marked, and appear much later. Another series of experi- 

 ments was carried on with a view of ascertaining the minimum amount of the oil neces- 

 sary to kill the worms. Pure kerosene, or strong kerosene water, when sprayed upon 

 the worms, has very much the same effect as benzine, yoang worms collapsing at once 

 and dying in less than two minutes. Old worms are not so quickly killed ; they do not 

 show any signs of pain, and die without falling into violent convulsions. The effects 

 of diluted kerosene water on average-sized worms are not instantaneous, as with 

 pyrethrum, but if the worms are not affected within 15 minutes after application they 

 have either not come into contact with the oil, or the mixture was too weak to have 

 any effect. For very young worms, i. (^., not over two days old (in the month of Sep- 

 tember), a very weak mixture seems to be sufficient, but with the growth of the 

 worms the resisting power is considerably increased. The mixture of 1 part of the 

 oil to 160 parts of water is not sufficient to kill the average-sized worm, if applied in 

 very fine spray and in moderate quantity; that of 1 part of oil to 120 parts of water 

 is sufficient to kill the worms, but in all cases where I applied this mixture so as to 

 kill the worms the leaves were considerably injured. 



The improvement made in the atomizing macliines, which obviates 

 entirely the danger of clogging, suggests another method to lessen the 

 injurious influence of the kerosene on the plant, viz., by the addition of 

 a quantity of very finely sifted wood ashes to the kerosene water, the 



