NURSERY STOCK FOR SHIPMENT. 55 



larv8e and pupae of the white fly. To destroy the eggs, however, he 

 found that a hirger dose was necessary. The author fully concurs 

 with Professor Gossard in his recommendation to defoliate completely 

 all white fly infested nursery stock before shipping, and, as an extra 

 precaution, to fumigate. The almost invariable experience of Florida 

 nurserymen, however, shows that citrus trees should not be fumigated 

 with roots bare. The fumigation is far less necessary than when the 

 insects concerned are true scale insects and are attached to the stems. 

 White flies have never been known to reach maturity except on the 

 leaves, although eggs and crawling larvae may occasionally be found 

 on young growing shoots. It is safe to presume that there are no 

 unhatched eggs of the white fly on anything other than leaves and 

 young succulent growth of stems. When these are completely re- 

 moved there need be no fear that the pest will be carried by means 

 of the trees. The entire leaves, including the winged leaf petioles, 

 must be removed, and when large shipments are concerned careful 

 attention must be given to this. A greater danger than the trees 

 themselves is found in the packing. This, as Professor Gossard 

 points out, might be a possible source of danger if infested citrus 

 leaves were allowed to get into the moss or other material used in 

 packing. The danger is, of course, slight, but should nevertheless 

 be borne in mind by shippers and buyers of nursery stock. 



PRECAUTIONS. 



As is customary in publications on entomology in which the use of 

 potassium cyanid is recommended in combating insect pests, atten- 

 tion is directed to the extremely poisonous nature of this substance. 

 There are on record no fatalities due to the use of potassium cyanid 

 as an insecticide against orchard pests, but this is because the danger 

 from careless use was well known and simple precautions were 

 observed. In weighing the doses it is recommended that the hands 

 be protected b}' leather gloves, and after starting the generation of 

 the gas the operator should avoid breathing until he is outside in the 

 open air. A slight choking sensation experienced when standing 

 close to the tents during the fumigation acts as a danger signal, and 

 one should not persist in remaining where the gas is dense enough to 

 produce this result. The acid should always be handled with great 

 care. In addition to precautions necessary for the safety of the 

 operators, care should be taken to avoid the scattering of small parti- 

 cles of the cyanid where fowls or other animals might become poisoned. 

 As this substance is readily soluble in water and is deliquescent, or 

 capable of liquefying through the absorption of moisture from the 

 air, small particles accidentally dropped soon disappear. 



