8 Farmers’ Bulletin 1282. 
TIME OF APPLICATION. 
Since the fumes of nicotine in this dust must be depended upon 
to kill the insects, two factors are of importance in its application, 
viz, the stillness of the air and the temperature. The longer the 
cloud of dust remains around the infested plant, the more likely 
the insects are to be killed by the fumes. On the other hand, if 
a wind is blowing, not only the cloud of dust itself, but the fumes 
also, will be blown away. Therefore it is desirable to apply the 
dust when the air is still. Usually this is early in the morning or 
just at dusk. At these times, also, the humidity being higher, the 
dust remains close to the ground. 
The effectiveness of the dust is also dependent on the volatility of 
the nicotine, which is greatly increased at a high temperature, re- 
sulting in a much quicker and more thorough killing. Hence, from 
this standpoint alone, the application is best in the warmer portion 
of the day. If, however, a breeze is blowing, the value of the tem- 
perature may be entirely offset by the rapid diffusion of the fumes. 
Dust should not be applied either when the wind is blowing or 
on a day when the outdoor temperature is much below 65° F. 
NUMBER OF APPLICATIONS. 
Such insects as aphids and thrips reproduce very rapidly. No 
matter what method of control is used, therefore, whether it be 
dusting or spraying, under conditions favorable to the insect a re- 
infestation may take place, even though a high percentage may 
have been killed. On this account it is not to be expected that at 
- all times one dusting will be sufficient for an entire season. Some-~* 
times one application will be sufficient, but it may be necessary to 
dust twice or even three times. In fact, many growers plan for 
a second application, timing it to check the second infestation be- 
fore it begins to be serious. 
All dusting and spraying should be done with the idea of prevent- 
ing infestation and the resulting damage rather than trying to stop 
an infestation after it has become heavy. This is always the easier, 
cheaper, and more profitable way. If the grower waits until the 
field is quite generally infested before starting control measures, 
even though practically all the insects present are killed, it is prob- 
able that they will have already done considerable damage to the 
plants and reduced the crop accordingly. The grower, then, may 
feel that the control measures were not worth while, whereas, if 
they had been undertaken earlier, the damage would have been 
prevented and a larger crop produced. 
