30 FARMERS BULLETIN 848, 



TOPPING OF PLANTS. 



The practice of topping plants is sometimes recommended for 

 fields infested by the boll weevil. The results of work hj different 

 experiment stations have shown that topping has exceedingly im- 

 certain general results. As often as otherwise it decreases instead of 

 increasing the crop. In any case the topping of plants can probably 

 do no harm in fields that are being damaged by the weevil. It is 

 probable that the general results will be beneficial in causing the 

 more rapid growth of the crop on the lower and middle branches. It 

 has never been possible to demonstrate this in an exact way. Never- 

 theless, for the general effects stated, the topping of plants is included 

 among the recommendations that should be followed, although as one 

 of minor importance. 



COTTON LEAFWORM AND BOLL WEEVIL. 



The relation between the leaf worm or so-called "army worm"* 

 and the boll weevil deserves special attention. A quarter of a century 

 ago the efforts of entomologists and planters were directed toward some 

 means of destroying the leaf worm. The use of Paris green was found 

 to be effective. Various changes in the general sj'-stem of cropping cot- 

 ton also caused the injuries by the leaf worm to become less conspicuous 

 year after year. Even up to the time of the spread of the weevil into 

 Texas, however, poisoning was a more or less regular operation on all 

 cotton farms. The insects never did any considerable damage before 

 the middle or latter part of the season. The reason for destro3^ing the 

 leafworm was that it prevented the maturity of a fall crop. For 

 this reason the saving of the top crop, and in exceptional seasons a 

 part of the middle crop, was aU that was desired. The work of the 

 boll weevil has changed aU this. After the careful studies that have 

 been given the problem, it is evident that no top crop of cotton can 

 be expected in infested regions. This, of course, reduces the leaf- 

 worm to an insect of little importance where the boll weevil exists. 



The change has actually been even greater than this, for the work 

 of the leafworm has a disastrous effect upon the boll weevil. As 

 has been pointed out in the discussion of fall destruction, the late- 

 developing weevils are the ones that pass tlu-ough the winter. Con- 

 sequently, if the leafworms defoliate the plants and stop the forma- 

 tion of squares, a certain degree of fall destruction is accomplished. 

 It can never be as satisfactory as the poorest artificial fall destruc- 

 tion, because the plants continue to leaf out after the defoliation by 

 the worms, thus giving the weevils a supply of succulent food. It is 

 not recommended that the work of the leafworm be depended on in 

 place of fall destruction. Nevertheless, allowing the leafworms to 

 proceed with their work, or even encouraging them, will assist as a 



Alabama argillacca Iliibner. 



