16 RELATION OF DROUGHT TO WEEVIL RESISTANCE IX COTTON. 



weevils as early as possible of food and of facilities for breeding. If 

 this work is postponed until the plants are killed by frost, much of 

 the advantage of removing the stalks is lost, though it may still be 

 very important to destroy the unripe bolls, which sometimes carry 

 many weevil larva? through the winter. In some districts the pastur- 

 ing of the cotton fields in the fall is very useful, for the cattle eat the 

 buds and green bolls with the weevils and larva? that might otherwise 

 be left in the fields. 



Another factor that tends to limit late planting in Texas is the 

 prevalence of root-rot. As the attacks of this disease are often 

 deferred till the latter j^art of the season, the plants that are killed 

 may not represent a total loss. Some of their bolls may be ripe 

 before the plants are killed, and the remainder are opened prema- 

 turely by drying, so that the lint, though often weak and worthless. 

 can be picked and sold with the rest of the crop. In some parts of 

 Texas fields are often seen with half the plants dead from root-rot 

 before the middle of September, though half or three-quarters of the 

 crop may be already mature. If the crop were to be deferred by 

 late planting, root-rot injuries might involve a total loss. In such 

 cases the root-rot. rather than the boll weevil, may be said to deter- 

 mine the necessity for early planting. 



RELATION OF DROUGHT TO WEEVIL-RESISTANT HABITS OF 



GROWTH. 



Recognition of the importance of dry weather brings a new factor 

 into the question of weevil-resistant habits of growth. If it be con- 

 sidered a matter of first importance to lessen the number of weevils 

 that go into hibernation in the autumn, it appears to be essential to 

 use the earliest and most determined varieties, so that the crop can 

 be completed at the earliest possible date, and thus leave the weevils 

 without opportunity to breed for as long a period as possible before 

 winter. It happens, however, that some of the best of the early 

 varieties, such as the Triumph cotton of Texas and the Kekchi cotton 

 of Guatemala, have low. compact habits of growth that undoubtedly 

 tend to interfere with the beneficial effects of dry weather in killing 

 the weevil larva?. Fallen squares are much more effectively shaded 

 by a low. contact plant than by one that bears its foliage farther up 

 so that all of the ground tinder the plant is exposed directly to the 

 sun during at least a part of the day. Plants that stand well up 

 from the ground and allow the sun to reach and dry out the fallen 

 squares and kill the weevil larva? are able to secure in this way a dis- 

 tinct advantage over the low. compact plants that shade the fallen 

 squares and protect them from the dry winds. 



Many of the experimental plats at San Antonio in 1909 consisted 

 of Triumph cotton. The low. compact form of the plant- was well 

 220 



