142 FROGIIOPPER BLIGHT OF SUGAR-CANE. 



I have experimented with various strengths of nicotine (Black 

 Leaf 40) solution, and found that at certain concentrations, particularly 

 when small traces of soap and ammonia are present, it will kill nearly 

 all the nymphs with which it comes into contact, but the cost of the 

 solution at the concentration required was almost prohibitive. 



Gough recommends the use of kerosene emulsion for destroying the 

 adults, but, I am not aware that any extended trials have been made of 

 this method, which might be practicable on a small scale. 



Carmody and others in 1912 experimented with Nitrolim, an artificial 

 manure containing nitrogen and lime. About two ounces were applied 

 to each stool particularly on the visible nymphs, and in some cases the 

 results were said to be satisfactory. The advantage of this method is 

 that the material applied is a manure and thus no extra expense is 

 involved. Its disadvantage is that probably only the nymphs actually 

 touched by the powder will be killed. The chemical has been unobtain- 

 able during the last few years, and I have unable to test it. 



In 1918 Mr. Glasgow of Orange Grove Estate reported that he had 

 a secret liquid that would destroy all the froghopper nymphs and eggs, 

 but my tests of it and the results of his field demonstrations were not 

 satisfactory {see "Williams 1919 B.). In the following year Mr. Glasgow 

 patented his liquid, in which the active substance is corrosive sublimate 

 with hydrochloric acid and common salt. I made a few laboratory 

 experiments, and found that it was of no value in destroying nymphs 

 but eggs dipped in it for one minute failed to hatch. 



All these methods of spraying liquids round the stools suffer from the 

 common disadvantage of the cost of application and the labour required 

 when all available hands are needed for other work. 



A number of experiments were made with spraying machines at 

 St. Augustine with the assistance of Mr. J. B. Piorer, and we came to 

 the conclusion that an average of half a minute per stool is required 

 and that the plants cannot be properly sprayed at a higher rate than 

 twelve plants to the gallon of liquid. 



With six men s^jraying, two at the central pump for filling and 

 mixing the liquid, and one man with cart bringing water, about two acres 

 per day can be done. This would cost about $2 per acre for labour in 

 addition to the cost of 200 gallons of liquid (allowing 2,400 stools 

 per acre). 



The ground cannot be covered with sufficient rapidity, and the cost, 

 particularly if more than one application is necessary, is too great. 



The use of small cups for pouring the liquid round the stools from 

 buckets, as used by Mr. Glasgow, is less expensive, but also less efficient. 



It must also not be forgotten that the sprays will almost certainly 

 destroy the grubs of the Syrphid fly and so reduce one of the natural 

 checks on the froghopper's increase. 



Stamping out of Nymphs. On some estates children armed with 

 short sticks are sent through the infested fields to crush every visible 

 froth mass with the end of the stick. The method is not expensive, but 

 only froth masses on the surface are destroyed and in these friend 

 and foe alike are killed. 



It is doubtful if the method would be of any value in the case of a 

 severe widespread outbreak, owing to the labour required. 



Hand Collecting. Still more laborious is the method of sending 

 children through the fields to collect the nymphs from the froth masses 



