184 Maine Agricultural Experiment Station. 1920. 



be obtained. Plant at least part of it in a seed plot of sufficient 

 size to furnish seed for the next year's planting. Select land 

 for this purpose as remote from all other potato fields as pos- 

 sible and land which has not grown potatoes for one or more 

 years. Give the seed plot special care. Rogue all mosaic plants 

 from the seed plot as soon as they show the disease. In case 

 aphids are unusually abundant, the spreading of mosaic by them 

 possibly would be reduced by controlling them with suitable 

 spraying methods, which are advised for the seed plot every 

 year inasmuch as even a small and inconspicuous number of 

 aphids may spread mosaic. Such spraying methods, according 

 to recent publications upon this question 18 , require adding ^ 

 pint of "Black Leaf 40" or of a similar nicotine preparation to 

 each 50 gallons of bordeaux mixture. In localities where it is 

 feasible to make a separate spray for aphids, the y^ pint of nico- 

 tine solution is more effective if added to 50 gallons of water 

 containing 2 pounds of laundry soap first dissolved in hot water. 

 Moreover, if preferred, kerosene emulsion may be used instead 

 of the nicotine spray. Regardless of whatever spray is used 

 for plant lice, it is essential that it be applied in such a manner 

 that it reaches the insects themselves, since the effectiveness of 

 the spray depends upon contact. Hence it is necessary to have 

 the nozzles arranged on the spray boom so as to cover the under 

 sides of the leaves and the stalks of the plants, as well as the 

 upper leaf surfaces, with the spray materials. Finally, avoid 

 any chance of mixing the seed-plot stock with the rest by har- 

 vesting and storing it separately from the general stock. Repeat 

 this each year. 



ls Britton, W. E. Eighteenth report of the state entomologist of Con- 

 necticut for the year 1918. Connecticut Agri. Exper. Sta. Bui. 211 :249- 

 352. Figs. 7-13. PI. 21-36. 1919. 



Britton, W. E., and Zappe, M. P. Kerosene emulsion versus nicotine 

 solution for combating the potato aphid. Jour. Econ. Entomology 12 :71- 

 81. 1919. 



Houser, J. S., Guyton, T. L., and Lowry, P. R. The pink and green 

 aphid of potato. Ohio Agri. Exper. Sta. Bui. 317. 21 figs. 1917. 



Patch, Edith M. Spray pink and green potato aphids. Potato Mag- 

 azine l 12 :8-9, 31. 1919. 



Regan, W. S. Potato plant lice and their control. Massachusetts 

 Agri. Exper. Sta. Bui. 177:135-146. 1917. 



