48 EXPERIMENTAL FARMS 



9-10 EDWARD VII., A. 1910 



Since 1906, the Nova Scotia Department of Agriculture has been most active in 

 its endeavours to rid the province of this dreaded pest. The following letter gives 

 concisely the present state of the Brown-tail Moth in that province. 



Truro, N.S., June 14, 1909. — ' During the year we have had reported to us as 

 destroyed, after a very careful search, about 750 Brown-tail Moth nests, as compared 

 with about 6,000 two years ago, and 4,000 last year. I should also add that this 

 season's search was the most thorough which we have yet made. It would accordingly 

 appear that unless something unforeseen happens, we are making some headway in 

 fighting this pest. Practically all nests have been discovered between Middleton, 

 Annapolis count;/, and Digby, Digby county, and the majority in the vicinity of 

 Bear River, Digby county. — M. Gumming, Secretary for Agriculture.' 



In another letter, Prof. Cumming stated that he had received a number of nests 

 from oak and other forest trees. For two years a bounty had been paid on every nest 

 collected, but during the present year this was discontinued, and instead, as is stated 

 by Prof. Cumming in a letter dated March 20: 'We have now got down to what 

 might be termed house to house work, which is being done by graduates of our own 

 college.' 



Mr. Gibson deserves great credit for the hearty enthusiasm he has thrown 

 into this work and for the patient and thorough examination he has made of an 

 enormous amount of material. 



EXPERIMENTS WITH HYDROCYANIC ACID GAS TO KILL THE LARV.E OF THE BROWN-TAIL MOTH. 



(By Arthur Gibson, Chief Assistant, Division of Entomology and Botany.) 



In order to test the value of fumigation with hydrocyanic acid gas, to kill the 

 caterpillars of the Brown-tail Moth, the following experiments were conducted : — 



February 26, 1909. — Two nests on pear seedlings, which had been put in a large 

 wide-mouthed glass jar, with cheese-cloth covering, were fumigated at the same 

 strength as is used in the federal fumigation stations, viz. : 1 ounce of cyanide of 

 potassium, 1 ounce of sulphuric acid and 3 ounces of water, to every 100 cubic feet 

 of air space. The fumigation box which was used is 4 feet high, 4 feet wide and 8 

 feet long = 128 cubic feet. The amounts of chemicals used were 1% ounces cyanide 

 of potassium, 1^ ounces sulphuric acid and 3| ounces of water. The nests were 

 exposed to the gas for 45 minutes, and afterwards when opened and examined the 

 larvae were all found to be alive. 



February 27. — Two different nests on pear fumigated. Chemicals used: 2 ounces 

 of cyanide of potassium, 2 ounces of sulphuric acid and 4£ ounces of water, for the 

 128 cubic feet in box. Exposure 55 minutes; no larvce killed. 



March 2. — The two nests fumigated on February 27 were again submitted to the 

 same strength, but the exposure was for 45 minutes. A few caterpillars had emerged 

 from the nests and were on the outside of the same. Result : none killed. 



March 12. — The same two nests were fumigated a third time. The strength was 

 increased to 2h ounces of cyanide of potassium, 2£ ounces of sulphuric acid and 7£ 

 ounces of water to the 128 cubic feet of space. The exposure too, was lengthened to 

 one hour. Many of the caterpillars had left the nests and were resting on the sides 

 of the jar. One small parasite was found alive in the jar, just before the fumigation 

 took place. This, of course, had not been affected by the two previous fumigations 

 to which these nests were subjected. Result: thirty dead larvae in the jar after the 

 fumigation, which was about one-fourth of the number of living caterpillars which 

 had occupied the nests. 



March 15. — The remaining larvae in the same two nests were fumigated a fourth 

 time. The strength used was the same as on March 12, but the exposure was 

 lengthened to two hours. Many of the caterpillars were active on the sides of the 

 jar. Result: only twelve dead, although several others were apparently without much 

 life. 



