TOBACCO DISEASES AXD THEIR CONTROL. 



15 



soil treatments, but none applicable to practical conditions lias 

 proved satisfactory. 



Badly infested fields should be cropped for at least five years with 

 crops not attacked by wilt, before replanting to tobacco. Four-year 

 and three-year periods of cropping may suffice on land not too 

 heavily infested. A second crop of tobacco in succession on in- 

 fested soil is almost certain to result in failure. The wilt disease 

 attacks tomatoes, potatoes, peanuts, peppers, eggplants, velvet beans, 

 and garden beans. These crops therefore should not be grown in 

 rotation with tobacco on infested ground. Bagweed, jimson weed, 

 and certain other weeds are also attacked and should be carefully 

 controlled on infested land intended for tobacco. Such crops as 

 corn, wheat, rye (as a cover crop), sweet potatoes, cowpeas, grasses, 

 red and crimson clover, and cotton may be safely used in rotation 

 on infested land. General sanitary measures should also be used, 

 aiming especially to prevent plant-bed infection by giving due re- 

 gard to the location of beds with reference to infested fields and the 





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cO^Er^^S! 



Wj^mM^W 





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Fig. 9. — Fusarium wilt of tobacco. This disease resembles Granville wilt in many 

 respects. Pressure on the cut ends of stalks does not yield an ooze. 



sterilization of seed-bed soil, 

 as fertilizer should be avoided. 



The use of tobacco stalks or steins 



FUSARIUM WILT. 



Description. — This recently described disease of tobacco was first 

 definitely noted in Maryland, but it has also been found in Ohio, 

 Kentucky, and Tennessee. The disease does not seem to be of com- 

 mon occurrence even in these districts, although in a few isolated 

 cases as much as 20 per cent of the plants in a field was destroyed. 

 The disease is a typical wilt and has been called Fusarium wilt 

 (naming it from the causal organism) to distinguish it from the 

 ordinary tobacco or Granville wilt previously described. 



The general symptoms of this disease are much like those of Gran- 

 ville wilt, except that on cutting and pressing the infected stalk no 

 slimy ooze is extruded from the vessels, as is common in the case of 

 Granville wilt. Fusarium wilt may first become evident upon very 

 young or upon mature plants. Under field conditions it is probable 

 that infection occurs soon after transplanting, but that marked 

 symptoms may be delayed for several weeks. In large plants the 



