22 BULLETIN 833, U. S. DEPARTMENT OF AGRICULTURE. 
When a severe infestation is encountered the most heavily infested 
plants should be taken out immediately and burned. 
This should then be followed by either fumigation or spraying as 
outlined below. 
Fumigate every night, with either nicotine papers or hydrocyanic- 
acid gas, for a period of at least six weeks. This will kill all the 
adults that emerge during such a period and at the same time will 
prevent the further laying of eggs for future generations. The 
dosage need not be very heavy in either case. When nicotine papers 
are used one sheet to every 1,000 cubic feet of space will suffice. 
If hydrocyanic-acid gas 1 is employed, one-eighth to one-fourth ounce 
per 1,000 cubic feet will kill all of the adults. The use of hydro- 
cyanic-acid gas is not recommended unless in the hands of a competent 
fumigator, owing to its deadly poisonous effects. Too much emphasis 
can not be laid on the fact that the fumigation must be set off after 
12 o’clock, midnight, to be effective. It is preferable to start the 
generation between the hours of 12.30 a.m. and2a.m. Any fumi- 
gation done before midnight would be useless for it has been pointed 
out that the adult does not emerge until after midnight. On the 
other hand, if it is started later than 2 a. m. many adults will have 
emerged and laid their eggs. 
Tn case fumigation is not advisable, especially where chrysanthemum 
plants are isolated or when other varieties of plants are present in the 
houses, spraying is recommended. This must be done consistently for 
a period of four to six weeks, a 40 per cent solution of nicotine sul- 
phate extract diluted (1-800) being used, and soap added at the rate of 
one-half to 1 ounce per gallon of solution. - The application should be 
made late in the afternoon in order that the best results may be 
obtained. In this manner practically all adults can be killed at the 
time of emergence and any eggs present will be destroyed. 
PREVENTIVE MEASURES. 
It has been proved that the means of disseminating this insect 
has been the shipment of infested chrysanthemums, both plants and 
cuttings. Interceptions made by the various State inspection 
officials, as well as by inspectors of the Federal Horticultural Board, 
definitely confirm this fact. It is therefore imperative that only 
clean plants and cuttings be brought into commercial houses where 
chrysanthemums are growing or to be grown. Growers should care- 
fully examine all chrysanthemums received and see that all material 
intended for shipment or distribution is free from this pest. Any 
questionable material should at once be submitted to the State 
1 For further information on the use of hydrocyanic-acid as in fumigating greenhouses, see Farmers’ 
Bulletin 880. 
