PEACH SCAB AND ITS CONTROL. 63 



Primary infection results from conidia from overwintered twig 

 lesions. Spores from lesions of the current year's production may 

 induce secondary infection. 



The fungus overwinters in the mycelial stage in the lesions on Hving 

 twigs. There is no evidence that any other type of overwintering is 

 of any practical importance in the life history of the parasite, although 

 it has been shown that the myceHum may survive the winter on fallen 

 fruit and twigs. 



Peach scab occurs at its worst in temperate sections where the 

 spring and early summer are moist and the growing season is long. 

 It is much less prevalent in dry sections and in high altitudes where 

 the opposite conditions obtain. 



Varieties vary markedly in the degree to which they are subject 

 to scab injury. In general, early varieties are not very seriously 

 affected. Midseason varieties may be moderately or severely at- 

 tacked. Late varieties are usually the most severely affected. The 

 period of exposure of the fruit to the attack of the fungus is a major 

 factor in these differences. There are, however, varietal differences 

 which are independent of the ripening- period of the fruit. These 

 have not been explained. 



It has been shown conclusively that the disease may be controlled 

 in a highly satisfactory manner by spraying with self -boiled lime- 

 sulphur or with finely divided wettable sulphur and that the scab 

 treatment may be satisfactorily combined with the control of brown- 

 rot and the plum curculio. (For su mm arized reconunendations, 

 see pp. 59-60.) 



Under average conditions, the cost of spraying 7-year-old to 10- 

 year-old peach trees for scab, brown-rot, and the plum curculio 

 (three treatments, as recommended on pp. 59-60) should not exceed 

 5 cents a tree. 



In the writer's experience, the merchantable fruit from trees 

 properly sprayed in accordance with the foregoing recommenda- 

 tions has rarely amounted to less than 95 per cent of the total yield, 

 even under severe conditions, while its quality has uniformly been 

 much superior to that of the unsprayed product. 



