THE SMALL FRUITS OF NEW YORK 21 



the mosaic disease that in recent years has caused great losses in potatoes, 

 tomatoes, cucumbers, tobacco, and others. The mosaic in raspberries is 

 not spread from plant to plant thru the air or soil, or by contact. The only 

 known method of infection is by plant-lice or aphids which carry the infective 

 material from diseased to healthy plants. From the time of infection all 

 of the future growth made from the canes and roots from year to year 

 becomes more sickly. The new canes are dwarfed and the leaves show 

 small irregularly shaped areas of yellow-green. The leaves, also, are often 

 blistered, curled, and wrinkled. 



" Mosaic spreads in certain varieties more rapidly than in others. The 

 Herbert and Ranere (St. Regis) are the outstanding red varieties which are 

 usually found free from mosaic under commercial conditions. The rela- 

 tive rate of spread of mosaic in varieties as observed in New York is 

 as follows: Very slow, Herbert and Ranere; slow, Erskine Park and New- 

 man; moderately slow to rapid, Cuthbert, Columbian, Empire, Golden 

 Queen, June, Ontario, and Owasco; rapid, Cayuga, Latham, Marlboro, Per- 

 fection, and Seneca. 



" The effect of mosaic upon the plant is independent of the rate of spread 

 in the variety. For example, plants of Herbert, Golden Queen, Owasco, 

 Marlboro, and Columbian are severely affected once they become diseased, 

 while plants of Perfection, Latham, Ontario, and to some extent the Cuth- 

 bert often produce vigorous canes for several years after infection. 



■' Removing the affected plants from one- or two-year-old plantings has 

 proved to be a successful method of propagating mosaic-free nursery stock. 

 The rate of spread of mosaic into experimental plantings of such stock in 

 New York varies greatly, even on adjoining farms. It appears that condi- 

 tions where the raspberry aphid is the only aphid which is common, the 

 rate of spread from a distance into the new mosaic-free planting is very 

 slow. In other localities where one or more species of winged aphids 

 migrate to raspberries in large nvmibers from other plants there has been 

 often a rapid increase to over fifty per cent mosaic in one j^ear. It is 

 unwise to interplant with crops that are known to be susceptible to mosaic. 

 In order to control raspbeny mosaic successfully in susceptible varieties 

 more must be learned of the aphid carriers, their habits, food plants, and 

 methods of preventing their migration to raspberries. Resistance to mosaic 

 combined in the same variety with other commercially desirable characters 

 may be supplied eventually by the plant breeder. 



"There are two other diseases of raspberries, leaf-curl and streak, which 

 are carried by aphids and which cause the running-out of varieties. Leaf- 

 curl is prevalent in Cuthbert but is not often found in other varieties. The 

 canes are more severely dwarfed than by mosaic, the leaves are crumpled 

 and dark green, and the fruit is worthless. Streak is a disease of black 

 varieties which resembles mosaic in its effect on the plant. The canes are 



