22 The Bulletin. 



ing have been referred to. Some have held that too much nitrogen fertil- 

 izer predisposes the plants to the wilt, and that a relatively large 

 amount of potash will have the opposite effect. There is no conclusive 

 evidence that the fertilizers commonly used in tobacco culture greatly 

 favor the disease; certainly they alone do not cause it. Rainy weather 

 and low, moist situations are favorable to the progress of the disease. 



Control. — Make the seed bed in uninfested spots. The common prac- 

 tice of using newly cleared land and burning it well is a safeguard. 

 Make sure that drainage water from infected fields can not reach the 

 seed bed. Such water is not safe for use in transplanting; on the seed 

 bed it may undo the work of sterilizing by burning the bed. If there is 

 any suspicious development in the seedling plants do not use any for 

 setting in uninfested fields. Be very cautious about using plants grown 

 by other people. By early transplanting much of the loss is sometimes 

 avoided. Avoid root injury in transplanting and cultivation. Guard 

 against any transfer of infected soil on farm implements or vehicles or 

 the feet of stock. Clean the implements; disinfectants may sometimes 

 be used on them to advantage, such as formaldehyde, 1 pint in 8 gallons 

 of water, or carbolic acid, 1 pint in 5 gallons, or bluestone, 1 pound in 4 

 gallons. In infected fields try to control insects to the fullest extent. 

 Remove and destroy affected plants in as far as possible; each one har- 

 bors enough bacteria to kill hundreds of others if given the chance. Do 

 not let any contaminated refuse reach the barnyards or roads or streams. 

 It is important to prevent surface drainage from infected fields to val- 

 uable land. Handle sound plants before affected ones in topping and 

 suckering, and do this work in dry weather. Do not plant tobacco or 

 other susceptiUr crops on infected soil for four to six years. Crops that 

 require clean cultivation, <uch as corn or cotton, are probably best m the 

 rotation. Be sure that susceptible weeds are kept from growing. 



The following rotations* might be practiced with profit : 



For land slightly infected: 1. Tobacco, followed by winter oats. 2. Cow- 

 peas, followed by crimson clover. 3. Cotton, with crimson clover sowed at 

 last working or first picking. 4. Corn, followed by winter rye. 5. Tobacco, 

 followed by winter oats. 



For land badly infected: 1. Tobacco, followed by crimson clover. 2. Corn, 

 followed by crimson clover. 3. Cotton, followed by crimson clover. 4. Corn, 

 followed by winter oats. 5. Cowpeas, followed by grass mixture after liming. 

 6. Grass.f followed by winter rye. 7. Tobacco, followed by crimson clover. 



Attempts are being made to develop types of tobacco resistant to the 

 disease, but these have not yet given desired results. 



No practicable method of soil disinfection has been devised. Badly 

 affected plants are hardly good for anything except the making of 

 tobacco extract. The early harvesting of a crop may sometimes avoid 

 increased loss. 



•Outlined by Mr. E. G. Moss, Co-operative Assistant in Tobacco Investigations. 



tit may sometimes be best to keep the land in grass two years, thus lengthening this rotation. 



