242 



ceiitrically-marked spots upon the leaves, and when serious infection 

 occurs the leaves dry up and die. 



As shown on Map 99, it has been found in IT counties. 



The severity of the disease, as indicated by field observations, indi- 

 cates an injury equivalent to a 4 per cent reduction in the crop for each 

 of the years 1921, 1922, and 1923. Such a percentage, when applied to 

 the commercial product of 1921, the last year for which published figures 

 are available, represents a reduction in yield of 1.030 tons, equivalent to 

 the yield of 294 acres. 



Control is readily obtained by spraying with Bordeaux mixture, be- 

 ginning at the first sign of the disease and continuing the application every 

 3 to 10 days through wet weather. 



Wilt 

 Caused by Fitsariuui lycopcrsici Sacc. 



Wilt, the most destructive of the tomato diseases in Illinois, gains 

 entrance through the roots and penetrates the water-conducting tissues, 

 plugging them and causing a wilting, and finally the death of the plant. 

 A characteristic feature of the disease is the fact that besides causing the 

 plants to wilt it turns the sap vessels brown or black. Usually the dis- 

 ease does not become evident until after the fruit has set. 



This disease is known to have been in Illinois since 1911, in which 

 year Burrill reported that it was becoming very serious. Presumably he 

 referred to its occurrence in Union county. The following year he re- 

 ported it as wide-spread in southern Illinois, and according to C. E. Durst 

 probably 50 per cent of the crop was destroyed in Union county. 



Tomato wilt is now known to occur in 22 counties, the distribution 

 of which is shown on Map 100. It appears to be limited to the southern 

 two-thirds of the state, and is most common in the southern third. 



Field observations made in 1923 and 1923 indicated an injury equiva- 

 lent to a crop loss of 10 and 12 per cent respectively. If the average of 

 these figures be applied to the 1921 production it would mean a crop re- 

 duction of 3,055 tons, equivalent to the yield from some 870 additional 

 acres. 



The fungus causing tomato wilt persists in the soil after it is once 

 introduced, and control can be secured only through a rotation of crops, 

 whereby tomatoes are kept off the infected ground for several years. 



Le.\f Spot 



Caused by Septoria lycopcrsici Speg. 



Tomato leaf spot is wholly a disease of the leaves. It starts on the 

 lower part of the plant and eventually involves all the leaves. Those 

 severely spotted turn brown ami appear blighted, and when the disease 

 is severe throughout a patch serious damage results. 



