6 BULLETIN 124, U. S. DEPARTMENT OP AGRICULTURE. 



July 22 : Butterflies are very numerous now, filling the air everywhere. They 

 are even flying around over town in great numbers. Over an alfalfa field north 

 of town they are simply swarming. Millions of them present over the blooming 

 alfalfa where they are feeding. A field just across the road that had been 

 recently cut had the alfalfa covered with eggs. These are adults of the third 

 generation. 



Aug. 1 : Eurymus larvae are very abundant now and in a few fields beginning 

 to do considerable damage. On Mr. Aepli's farm 1 mile south of town the cater- 

 pillars were exceptionally numerous and damage considerable. However, 

 Mr. Aepli cut his crop of hay and stopped their work by disking. There were 

 257 larvae to the square yard counted in this field. 



In the Imperial Valley in 1912 the fourth hay crop, about August 

 1, was nearly one-third lessened by the feeding of the caterpillars, 

 but the damage, although heavier than in the previous year, in no 

 way compared with that of 1910 or 1913. During July, 1913, Mr. 

 Walter Packard wrote to the author, telling him of a great outbreak 

 around El Centro and suggesting that something should be done at 

 once, as practically all of the third crop had been destroyed. As 

 the writer was in northern New Mexico, engaged on other work, Mr. 

 R. N. Wilson was instructed to proceed to Imperial Valley and in- 

 vestigate the outbreak. Upon his arrival there he found the damage 

 to be very heavy, but over for the year, as the species had again been 

 checked by the disease. The conditions are best told in his original 

 field notes, which follow: 



El Centro, July 14, 1913: Some of the fields [alfalfa] were visited this 

 morning, and it immediately became obvious that if the bacterial disease is as 

 prevalent in all of the fields in the valley as in those visited this morning 

 it is now too late to try cultural methods, brush dragging, disking, etc., as 

 most of the larvae are dead. I am told that last week was very warm during 

 the entire week and that the humidity was high. This was probably just 

 the right condition for the disease to spread, and hence the cause of the death 

 of millions of the larvae. Many of the fields about El Centro have been cut 

 recently and so show nothing now as to Eurymus conditions ; many are 

 also being pastured, and in these the caterpillar attack is slight. In some 

 fields which have not been either pastured or cut the damage is considerable, 

 but very few healthy larvae or pupae can be found at present. Butterflies are 

 numerous everywhere, and in some fields they rise in clouds before the sweep- 

 net. That the damage from larvae to the present crop is about over is almost 

 certain. * * * A few farmers cut the crop after it had been stripped by larvae, 

 and the hay was of such poor quality that it was not even gathered. Much of the 

 hay that was gathered was of such poor quality and some of it was so foul 

 with diseased larvae that it was of little value. 



On July 16 Mr. Packard said that he noticed the " worms " in some num- 

 bers in the second crop at cutting time, about the last of May. The real 

 outbreak came in July, however, when the third generation of worms began 

 to eat the third crop of alfalfa. He noticed the bacterial disease in the fields 

 about the first week in July, when a large amount of damage had already been 

 done by the larvae, but the disease did not become widespread or really effec- 

 tive until after the hot, humid weather of last week. 



