PESTS OF TOBACCO. 257 



Worms having cocoons attached to them, resembling 

 grains of rice, should not be killed, as these cocoons be- 

 long to a family of parasites called Microgaster congre- 

 gata, which destroy the horn worms in great numbers. 



Catching the moths in traps, or poisoning the blos- 

 soms of petunia and Jamestown weeds with a sweetened 

 solution of cobalt (water one pint, molasses or honey 

 one-fourth pint, cobalt one ounce), diminishes the num- 

 ber of worms, but there will always be left enough to bo 

 troublesome. A drove of turkeys kept in the tobacco 

 field will destroy a great number of the worms, but the 

 only safety is in going over the field at least once a 

 week, or oftener, picking off the worms and destroying 

 them. The worms usually stay on the underside of the 

 leaf ; if a hole is seen in the leaf, no matter how small, a 

 worm will usually be the cause of it. The work cannot 

 be done too carefully, for if one or two worms remain 

 on a plant, they will completely riddle it in a very short 

 time. If they are well cleaned out when they first ap- 

 pear, much time and labor would be saved. 



Spraying tobacco with Paris green to destroy the 

 tobacco horn worm has engaged the special attention of 

 the Kentucky experiment station. The proportion used 

 was one pound green to 160 gallons of water. Plants 

 were thoroughly sprayed July 27 and August 3. There 

 were fewer worms on sprayed than on unsp rayed plants. 

 As to the amount of arsenic, only one-third of one grain 

 of arsenious oxide per pound of tobacco was the largest 

 quantity recovered by careful chemical examination. 

 Only four per cent of the arsenic originally applied was 

 recovered. As two to three grains of arsenic are required 

 for a fatal dose for an adult man, the station officials see 

 no harm in making these sprayings during a dry season. 



There are usually what farmers call two "showers" 

 of these worms, one coming about the last of June and 

 the other about the middle of August, or, rather, dur- 

 17 



