36 



equally under the tent, but tended to rise, leaving- near the g-round 

 a layer of insufficiently poisoned air. As this unequal diffusion of 

 the g-as has since been demonstrated in closed rooms, — a fact now 

 taken into account in the construction of fumig-ation houses, — it is 

 evident that we have here a serious objection to the whole process 

 of orchard fumigation for the San Jose scale. We now know that 

 peculiar methods and special precautions are necessary to secure an 

 equal diffusion of the gas, even in the air-tight rooms used in nur- 

 sery fumigation, and with the varied conditions and rapid work of 

 orchard fumigation it is clearly impossible to secure a uniform 

 action even in the average case. 



Details of the Work and its Results. — The following items con- 

 cerning thirteen representative orchards fumigated at Sparta are 

 taken from the field reports of the foreman and inspector. 



No. 1. On the place of Alvin Blair three hundred and ninety- 

 five trees, most of them peach, were fumigated from October 20 to 

 November 4. They were of medium size except a few of the apple- 

 trees, which were very large, requiring the use of two of the 

 largest tents lapped together over one tree and tied down with 

 ropes. The peach-trees had been severely cut back the preced- 

 ing* spring previous to spraying with whale-oil soap (see Plate 

 IX.), and the sharp stubs remaining punctured the tents, thus 

 making necessary constant inspection and frequent repair of leaks. 

 No doubt some gas escaped and some trees were imperfectly treat- 

 ed. A high wind was blowing when much of the work was done, 

 and great embarrassment was also caused by cold and rainy 

 weather, the tents tearing easily when wet and frozen. This 

 place was inspected September 10 of the following year (1900), 

 and badly infested peach-trees were found scattered through the 

 orchard, the wood of two years' growth sometimes almost incrusted. 

 In one row which was carefully examined the scale was found on 

 seventy-three per cent, of the trees. 



No. 2. On J. W. Robinson's place one hundred and seventy- 

 seven trees, thirty-six grape-vines, and seven shrubs were fumi- 

 gated October 18-20. This place had also been sprayed with 

 whale-oil soap early in May of the same year to check the spread 

 of the scale. September 10, 1900, twenty-seven trees were inspect- 

 ed, and scales were found on twenty-one. Two of these were very 

 badly infested, but it was surmised that these had been left with- 

 out treatment on the promise of the owner to destroy them as 

 worthless. 



No. 3. The place of Mrs. J. B. Hayer was probably the one 

 first infested in this whole region, one orchard having been com- 



