492 STATE BOARD OP AGRICULTURE. 



The spores Since spoi'cs are released from the sjiore cases when wet 



when'^we? tlic plants slioiild not be ''worked" until the plants are dry. 

 GroM'ers have reported cas-es where cultivation began at 

 a small infected patch and the disease was carried over 

 the entire field, and that in less than three weeks the entire 

 field was spotted. This is now readily explained. In green- 

 house practice, irrigation should replace the ordinary use 

 of the hose, 

 lordeaux^ After transplanting to the field, spray with 4-4-50 



Bordeaux mixture every 10 days. As has been shown, the 

 jieriod from time of inoculation to spore exudation is at 

 least 13 da3\s. Allowing this leeway for differences in period 

 of infection, it would seem that a spray so applied would 

 give the necessary protection. 

 Reasonsfor The greatest part of and the strongest infection results 



control/'^ from inoculation on the loAver surface of the leaf. There- 

 fore, all the precautions are less etfective if the plants are 

 allowed to run at will over the ground. The spraying of the 

 under side of the leaf is not accomplished unless the appli- 

 cation is tliorough. Failures to control the disease by spray- 

 ing are doubtless due to lack of thoroughness and timeliness. 

 How to spray. Spraying with 4-4-50 Bordeaux mixture in the fields 

 where tomatoes are staked should be extremely successful. 

 In tliis state spraying will not be most effective unless the 

 spray reaches the lower surface of the leaves. A sprayer 

 such as is used for potatoes, with two side nozzles set to 

 slioot upward and if practical, with one central nozzle to 

 spray doAvnward for each row will, under high pressure, be 

 most efficient in Michigan fields. 

 Spraying has Si)raying tomatocs with Bordeaux is a common practice 

 in M^k;h!gai?. in many tomato-growing centers. Wherever it has been tried 

 it has become a fixed part of the culture of the crop. No 

 grower can afford to risk his crop, and no company can afford 

 to risk its acreage. The spraying experiment of the College 

 in 1913 at Plymouth is a good example of what may be 

 accomplished. In tliis experiment "the plants that were 

 sprayed with Bordeaux mixture four times, produced 12.5 

 tons per acre while the plants that were not sprayed pro- 

 duced 5.2 tons per acre. The first spraying was made about 

 one month afler the plants were set in the field and fre- 

 quently enougli afterward to protect the new growth." 

 (Every ten days or two weeks).* 



Copper sulphate (Bluestone or Blue Vitriol) is a little 

 more expensive this year than formerly. In spite of the 

 cost, spraying is a crop insurance which is most strongly 

 to be advised. 



*Eustace, H. J., Mich. State Board of Agriculture Report 191-1 :234. 



