138 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



selection, amount of potassium chloride to the acre, and a useful biblio- 

 graphy of 114 numbers. — G. F. S.-E. 



Potato Leak (Potato Diseases). By W. A. Orton (U.S.A. Dep. 

 Agr. Circ. 23; January, 1909). — Considerable loss is occasionally 

 experienced from the rapid decay of potatos shortly after harvesting. 

 This trouble is locally known by the term "leak" or " melters." The 

 decay is due to the invasion of a fungus (Rhizopus nigricans). The 

 fungus can enter only through wounds, and potatos injured by careless 

 digging especially are attacked. The fungus is propagated by spores 

 produced in large heads, or sporangia. It can grow on a variety of dead 

 organic substances. It is known to cause decay in sweet potatos, 

 apples, and pears. As a remedial measure avoid breaking the skin of 

 the potato in handling ; avoid piling newly dug potatos in large piles 

 where they will " sweat." Keep the potatos dry and well ventilated. 



M. C. C. 



Potato Plant Louse. (Nectarophora solanifolii). By E. M. Patch 

 (U.S.A. Exp. Stn. Maine, Bept. 1907, pp. 235-257 ; figs.).— This aphis 

 is reported to have done great damage to potatos during recent years. The 

 insect attacks the upper parts of the plants and causes the shrivelling of 

 leaves, etc. A general account of the life cycle of aphides is given and 

 details concerning field and insectary observations. The winter host of 

 tbe species is at present unknown, but in captivity the insects fed on both 

 shepherd's purse and peas. It is regarded as impracticable to spray 

 large areas of potatos with paraffin emulsion or, so far, to attack the pest 

 through its winter host, but it is thought that clean cultivation including 

 autumn ploughing and burning old potato haulm may have a beneficial 

 effect. Various predaceous insects were found feeding upon it and 

 parasitic insects and fungi which destroyed the insects wholesale were 

 discovered. Technical descriptions of the various stages of the insect are 

 given. — F. J. C. 



Potato Scab. By W. J. Morse (U.S.A. Exp. Stn. Maine, Bept. 1907, 

 pp. 301-317; figs.). — The following table shows the results obtained by 

 disinfecting tubers : 





Lb smooth 



Lb. scabby 



Total from 

 plot 



Tev cent, 

 scabby 



Formalin solution : 











Seed scabby .... 



776 



5 



781 



0-6 



,, smooth . ... 



820-5 



6-5 



827 



0-8 



Formalin gas : 











Seed scabby .... 



822-5 



9.5 



832 



1-1 



,, smooth .... 



834 



3-7 



837-7 



0-4 



*Sodium benzoate : 











Seed scabby .... 



849-5 



106 • 



860-1 



1-2 



„ smooth .... 



855-5 



15 



870-5 



1-7 



Untreated : 











Seed scabby .... 



792 



55-1 



847-1 



6-5 



,, smooth .... 



819 



36-7 



855-7 



4-3 



* Soaked two hours in 15 gallons of water containing 20 ozs. of sodium benzoate. 

 The treatment in the other cases is detailed in the following abstract. 



