218 INSECTS AFFECTING FIELD CROPS 



hydrocyanic acid gas or with bisulfid of carbon may be employed. 

 (See page 61.) 



A species of aphis works on the roots of peanuts. This calls for 

 crop rotation ; the same land should be used for peanuts only once 

 in four or five years. (U. S. Farmers' Bulletin 356.) 



INSECTS ATTACKING TOBACCO 



Southern Tobacco Worm. This sphinx moth (Phlegethontius 

 sexta Johan.) is perhaps the most destructive insect with which 

 tobacco growers have to contend. In the larval stage it is a green 

 worm with seven oblique, whitish lines on each side. It is about 

 two inches long when full grown. On the posterior end of the 

 body is a prominent horn. It pupates slightly below the surface 

 of the ground. It emerges as a brownish moth with a few white 

 dots at the base of the front wings. There are two broods. The 

 winter is passed in the pupal stage. 



The Northern Tobacco Worm. This closely resembles the 

 above species and has practically the same life history and yields 

 to the same treatment. In the caterpillar stage it is a voracious 

 feeder and destroys an enormous number of plants. The two 

 insects cause an annual loss of nearly nine hundred thousand 

 dollars in the southern states. 



Enemies. Several insect parasites attack tobacco worms, 

 and the common skunk eats both larval and pupal forms. The 

 caterpillars are also attacked by fungous and bacteriological 

 diseases. 



Control. Three sprayings with arsenicals, preferably arsenate 

 of lead, or dusting the plants with powdered arsenate of lead is 

 recommended. When powdered arsenate of lead is used it should 

 be applied in the early morning, when the leaves are wet with dew. 

 It will be effective until washed off by frequent or copious rains. 

 All traces of this insecticide on leaves at harvest time should be 

 removed by spraying with water after sunset. Picking by hand 

 may be practiced where help is abundant and cheap. Hand-picking 

 among growers is perhaps more popular than treatment with 

 arsenicals. 



Bud Worm, Cotton Boll-worm, or Corn Ear-worm. In the 

 South this moth sometimes lays its eggs in the buds of tobacco, 

 the worm feeding upon the tender, unopened leaves. When treat- 

 ment is necessary, dusting the buds with cornmeal poisoned with 

 Paris green has been found most effective. About two teaspoon- 



