ECONOMIC ZOOLOGY ENTOMOLOGY. 259 



time nearly all the sprays were applied intensified the damage from the Paris 

 green, but the adjoining block treated similarly with arsenate of lead failed 

 to develop more than about 1 per cent of apples blackened at the blossom end. 

 In the picked fruit sprayed with ai'senate of lead, 3.8 per cent bore either cur- 

 culio crescents or codling moth wormholes, while 7.67 per cent bore these in- 

 juries in the plat sprayed with Paris green. Including both windfalls and 

 picked fruit, 96.18 per cent in the arsenate of lead plat and 93 per cent in the 

 Paris green plat were free from these injuries. This difference in cases of 

 heavy yields of high priced fruit is thought to justify the use of the lead, even 

 though the cost of the Paris green might be slightly less. 



There seems to be good evidence that arsenate of lead possesses some fungi- 

 cidal value as foliage was held on the trees in a vigorous condition late in the 

 fall, while unsprayed trees adjoining were stripped early in the fall by fungus 

 diseases. 



rumigation dosage for forcing crops, H. T. Febnald (Massachusetts 8ta. 

 Rpt. 1908, pt. 1, pp. 73, 7//). — A summary is here presented of hydrocyanic-acid 

 fumigation experiments with tomatoes and cucumbers under glass which ex- 

 tended over a period of 4 years. 



" Fumigation during sunlight can not be practiced without resulting in the 

 serious injury or death of the plants. Fumigation during cloudy days is very 

 unsafe at best and is not advised. Fumigation on moonlight nights is also 

 unsafe, frequently resulting in considerable injury. Good results are obtained 

 by fumigation on clear nights, without a moon, or on cloudy nights. The best 

 results are obtained by fumigation on clear, dark nights, with a house temper- 

 ature of from 55 to 65° F., followed by complete ventilation for from 15 to 30 

 minutes and a rather low temperature in the house the next day. Plants 

 fumigated while drops of water remain on them are likely to be injured ; fumi- 

 gation should, therefore, be given only to plants not so recently watered as to 

 have leaves or stems still wet. The moisture in the house (humidity) should 

 not be high, to obtain the best results. Under the conditions above named, 

 fumigation for tomatoes, using 0.01 gm. of 98 per cent potassium cyanid for 

 each cubic foot of space for a period of 40 minutes, should insure satisfactory 

 results, and the time with cucumbers could safely be extended to IJ hours with 

 advantage. 



" In general, the experiments show that with tomatoes the period during 

 which fumigation can safely be applied to the plants is hardly long enough to 

 more than kill the adult white fly, but a repetition of the treatment 3 times 

 at intervals of 2 weeks should be effective. With cucumbers, treatment can be 

 prolonged with safety, but it is doubtful if the eggs can be destroyed, using a 

 safe strength of the cyanid, and for this reason repetition of the treatment 

 as with the tomato is desirable." 



Analyses of Paris green and lead arsenate, C. S. Cathcart (New Jersey 

 Stas. Bui. 222, pp. 3-13). — All of the 17 samples of Paris green analyzed con- 

 tained the required 50 per cent of arsenious oxid combined with copper, but 

 7 samples indicated a lack of care in the process of manufacture. The average 

 composition of the 17 samples examined was : Total arsenious oxid, 55.26 per 

 cent ; water-soluble arsenic compounds, 1.66 per cent ; copper oxid, 28.81 per 

 cent ; and arsenious oxid combined with copper, 53.87 per cent. 



Fifteen samples of arsenate of lead analyzed showed the following varia- 

 tions: Water from 39.06 to 68.16 per cent, arsenic oxid from 6.07 to 19.71 per 

 cent, lead oxid from 21.13 to 40.08 per cent, soluble arsenic oxid from 0.05 to 

 0.28 per cent, and the soluble impurities other than arsenic oxid from 0.06 to 

 3.10 per cent. These results show that there has not been any decided improve- 

 ment in the uniformity of the various brands. 



