Nicotine Dust for Truck-Crop Insects. i 
Powdery mildew is a common disease of peas which is most suc- 
cessfully combated with sulphur. The use of a nicotine-sulphur 
dust, in which the carrier is about 70 per cent finely ground sulphur, 
will control not only the mildew but also the pea aphis. In parts of 
southern California peas are damaged by the beet army worm? and 
by cutworms. These may be combated, especially when the insects 
are young, by including in the mixture 10 per cent of powdered 
arsenate of lead. 
On cabbage, the nicotine dust will kill the aphis and also some cab- 
bage worms, but if the latter are numerous, the nicotine-arsenate of 
lead combination may be used. This is also effective against flea- 
beetles on tomatoes. 
Nicotine-sulphur dust should be used cautiously on cucumbers or 
melons, as more or less burning of the foliage may result, especially 
in very hot weather. This dust is partially effective against the red 
spider and is effective against mildew. 
ACTION OF NICOTINE DUST. 
The action of nicotine dust on insects is similar to that of nico- 
tine sulphate in a liquid spray, i. e., nicotine fumes or vapors, enter- 
ing the breathing pores of the insect, kill by paralyzing the 
nervous system. With the dust, this action becomes effective more 
quickly. Within a minute after the application, aphids and some 
other insects show evidence of extreme distress. Aphids elevate 
their abdomens as though trying to stand on their heads, and soon 
fall. Some beetles and small bugs lose the power of locomotion 
almost immediately, but continue to move their legs and antenne 
convulsively for a few minutes before becoming completely paralyzed. 
Because nicotine fumes are the active ingredient, killing is brought 
about in three ways: First, by covering, or partially covering, the 
body of the insect with dust: second, by covering the foliage or 
ground about the insect; third, by enveloping the whole plant with 
a cloud of dust which penetrates to all parts of the foliage. The 
first is obviously the surest method. With the material on the body 
of the insect, the nicotine fumes are certain to enter the spiracles, 
or breathing pores, causing almost instant death. The second and 
third methods, where the fumes suffocate or repel any insects in the 
immediate vicinity of the dust, are more like fumigation. As a mat- 
ter of fact, in the usual dusting operation all three conditions are 
present. The mere making of a cloud of dust about the plant, how- 
ever, is not sufficient. This cloud must be driven in and throughout 
the foliage in order to reach all the insects. 
* Laphygma exigua Hiibn. 
