Nov. 4, 1918 Fumigation of CaUleya Orchids 265 



EXPERIMENTS TO DETERMINE EFFECT OF FUMIGATION ON IMPORTED 

 CATTLEYAS AT TIME OF ARRIVAL 



A series of experiments under vacuum and normal atmospheric con- 

 ditions was conducted to determine what effect, if any, the gas would 

 have on the leaves, pseudobulbs, and general health of the plant. 

 Mechanically injured and sound plants were purposely fumigated with 

 excessive dosages to determine the appearance of fumigation injury. 

 To induce burning, the leaves were slashed and bruised with a hatchet. 

 Leaves so treated invariably exhibited blackened areas immediately 

 around the injured spot, and yellowing was evident where the food sup- 

 ply was cut off. This yellowing, however, was no more pronounced in the 

 fumigated plant than in the unfumigated ones, and was invariably con- 

 fined to the old or injured leaves. The experience of the writers ^\ith the 

 introductions of the Department of Agriculture has been that leaves on 

 plants which have been poorly ventilated for a long period slowly turn 

 yellow and eventually fall when exposed to the air. These leaves are 

 apparently devitalized by abnormal shipping conditions, and the dis- 

 coloration may be due to physiological changes. 



To demonstrate that fumigation is not responsible for the shedding 

 of all the leaves which are frequently found in containers when 

 delivered to the consignee a number of cases were carefully examined at 

 the port of entry. Two poorly ventilated cases yielded the following 

 count: (i) Number of plants, 42; total number of leaves, 304, of which 

 234, or 76 per cent, had fallen from the plants and were in various stages 

 of decay (PI. 20). (2) Number of plants, 69; number of pseudobulbs 

 on the plants, 719, of which 194 were dead; total number of leaves, 539, 

 of which 257, or 47 per cent, were dead. These figures represent fairly 

 well the condition of poorly packed orchids at the time of arrival, although 

 there are several instances on record where the entire contents of the case 

 were dead. 



Orchids fumigated in New York on May 27, together vnth controls, were 

 forwarded to Washington and held in a greenhouse. On July 30 both 

 the fumigated and unfumigated plants had lost 33 per cent of their old 

 leaves. As further evidence that fumigation with i ounce of sodium 

 cyanid does not kill the plants, if they are in a reasonably good condition 

 at the time of fumigation, a commercial orchid grower, on July 17, had cut 

 80 blooms from 700 plants of Cattleya trianae which were fumigated in 

 New York during the latter part of May. It is apparent, therefore, that 

 injury and shedding of leaves which might be attributed to fumigation 

 at the port of entry are in a large measure due to poor packing, improper 

 ventilation, and poor shipping conditions. This conclusion is further 

 supported by the summarized experiments given in Tables I, II, and III. 



