CHAPTER XIII 

 INSECTS INJURIOUS TO COTTON * 



Plant-lice f 



WITH the formation of the first true leaves of cotton, winged 

 aphids or plant-lice appear in large numbers on the under side 

 and on the terminals, the " buds " of the plants often being black 

 with them. Almost all of them are the common greenish Melon- 

 aphisj (see page 344), which infests melons later in the season. 

 It is evident, therefore, that the practice of planting cotton 

 between rows of melons is undesirable. The aphids migrate 

 to the cotton while it is young from various common weeds upon 

 which they have passed the winter. 



Another species, known as the Bur-clover Aphis occurs on 

 cotton at about the same time and is not readily distinguishable 

 from the previous species, but is darker and has a shining reddish 

 or brownish-black color. 



In cold weather these plant-lice often cause considerable 

 injury to the young plants, and greatly retard their development, 

 since they multiply very rapidly and feed mostly on the growing 

 terminals. If there be a few warm days, however, hordes of 

 small Hymenopterous parasites appear and in a few days often 

 completely rid the plants of the pest. 



Control. Although these aphids may be destroyed by spray- 

 ing with kerosene emulsion, whale-oil soap, or tobacco water, 

 as a rule the use of these on any considerable scale will hardly be 

 profitable. Keeping the fields clear of weeds by fall and winter 

 plowing will undoubtedly have a beneficial effect in reducing 



* See Hunter and Hinds, The Mexican Cotton Boll Weevil, Bulletin 51, 

 Bureau of Entomology, U. S. Dept. Agr.; Quaintance and Brues, The Cotton 

 Bollworm, Bulletin 50, Bureau of Entomology, U. S. Dept. Agr.; Sanderson, 

 Miscellaneous Cotton Insects of Texas, Bulletin 57, Bureau of Entomology, 

 Farmers' Bulletin 223, U. S. Dept. Agr. 



t Family Aphididce. 



t Aphis gossypii Glov. 



Aphis medicaginis Koch. 



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