June, '17] MORRILL: SOUTHWESTERN COTTON PESTS 311 



(Heliothis obsoleta), the cotton leaf worm {Alabama argillacea), the salt 

 marsh caterpillar {Estigmene acraa), the cotton boll cutworm (Prodenia 

 ornithogalli), the fall webworm (Hyphantria ci/?iea), the western army 

 cutworm (Chorizagrotis agrestis) the cotton leaf perforator (Bncculatrix 

 thurberieUa) and an undetermined bollworm which attacks the bolls 

 of the Arizona wild cotton. 



In their consideration of the distribution and destructiveness of 

 the cotton bollworm in relation to life zones, Quaintance and Brues (21) 

 say: "In Texas, from about the ninety-eighth meridian westward, the 

 bollworm rapidly becomes of less and less importance along with the 

 diminishing rainfall." In Arizona and California cotton-growing dis- 

 tricts the bollworm attacks corn as extensively as it does in the humid 

 eastern cotton states but for some as yet unexplained reason the insect 

 has thus far done very little damage to cotton in these sections. 

 It is noteworthy, however, that in the arid Laguna district in Mexico, 

 about 500 miles south of Phoenix at an elevation of 3,700 feet, the 

 cotton bollworm has during certain seasons caused heavy losses. 



The cotton leafworm was found on Thurberia plants in the mountain 

 canyons of southeastern Arizona, and on cultivated cotton in the Salt 

 River Valley and near Tucson in the summer of 1913. The next season 

 it was found in Graham County in eastern Arizona where cotton was 

 being tried out on a small scale about 75 miles from any other plantings. 

 The insect has not been found near Yuma although carefully searched 

 for and Mr. McGregor of the U. S. Bureau of Entomology informs me 

 that he failed to find a single specimen of the leafworm in the Imperial 

 Valley in 1916. In one instance the writer observed a Salt River 

 Valley Egyptian cotton field partially defoliated by the leafworm but 

 this was late in the season and apparently no material damage was 

 done to the crop. 



The salt marsh caterpillar is a common pest in Salt River Valley 

 cotton fields but there is no record of its injury to cotton elsewhere 

 in the arid Southwest. The injury from this insect is sporadic and the 

 occasional local outbreaks which have been noted have apparently been 

 due to the insects having completely consumed the supply of a preferred 

 food plant, a common weed known as the yellow-flowered ground 

 cherry {Phy salts angulata var. linJciana). 



The cotton boll cutworm and the fall webw^orm can only be recorded 

 as among those cotton pests present in Salt River Valley fields. The 

 actual damage noted in any case has been inappreciable. 



Cutworms did considerable damage in the spring of 1916 in one 

 locality in the Salt River Valley, necessitating the replanting of 

 several acres where the use of poisoned bran was not resorted to in time. 

 Attempts to breed out* the insects were unsuccessful but it is be- 



