CONTROL OF TOBACCO WILT IN THE FLUE-CURED DISTRICT. 3 



SYMPTOMS OF TOBACCO WILT. 



The disease affects the entire plant, leaves, stem, and roots, in a 

 characteristic manner. It may attack plants in any stage of de- 

 velopment, but usually symptoms first appear two to four weeks 

 after transplanting. During the period of rapid growth which fol- 

 lows as soon as the tobacco plants have become established after trans- 

 planting, the number of wilted plants increases rapidly, reaching 

 the maximum at about the usual time for topping. Under certain 

 conditions there are exceptions to this progressive increase of wilt. 



LEAVES. 



The first decided indication of the presence of wilt is the drooping 

 of one or more leaves of the plant. This wilting usually comes on 

 gradually, requiring several days to become prominent, and growers 

 familiar with the disease are often able to detect the first symptoms of 

 wilting a day or two before the layman would observe anything un- 

 usual about the plant. Affected leaves also may be somewhat distorted 

 and wrinkled. At first there is no discoloration, but the leaves 50011 

 become pale green, especially between the larger veins, and then the 

 leaf gradually turns yellow. Meanwhile the midrib and the veins 

 have become limp and droop in a characteristic, umbrellalike manner, 

 which persists even after the leaves and the stalk become brown and 

 crisp. In some cases the leaves on one side of the plant wilt first, 

 and sometimes only half the leaf is affected at first. 



STALK. 



In the early stages of wilt, if the tobacco stalk is cut across with a 

 knife the woody portion shows a yellowish discoloration, which be- 

 comes brownish or black as the disease progresses, especially in the 

 lower part of the stalk. By stripping off the bark the discoloration 

 appears as longitudinal streaks. In the advanced stages the pith also 

 becomes affected. The inner bark also decays, and as the wet rot 

 extends outward dry, blackened areas appear on the surface of the 

 stalk. Pressure on discolored stalks will force out from the cut ends 

 an opaque, dirty white ooze, very different in appearance from the 

 normal cell sap. 



ROOTS. 



The organism causing the disease enters the plant through the 

 roots, so that by the time the leaves begin to wilt the roots will show 

 more or less decay. When cut across with a knife the affected roots 

 in the earlier stages will show a dark discoloration in the woody por- 



