CORNELL UNIVERSITY EXPERIMENT STATION BULLETINS. 321 



mother who is perhaps calmly walking about or feeding. Many genera- 

 lions of these agamic females may be produced in succession, and it 

 lequires only eight or ten days for a generation. And further, as one 

 mother may give birth to one hundred young at the rate of four or five a 

 day it is easy to see with what astonishing rapidity these insects may often 

 multiply. 



The black peach aphis breeds thus agamically all the year rountl, and 

 no eggs nor males have been found. Only the wingless for'us occur upon 

 the roots where they breed freely and are to be found at all seasons of the 

 year, often a foot or more beneath the surface even in stiff clay soils; 

 sandy soils are however preferred by the pest. 



Early in spring as soon as the buds begin to swell, some of these root 

 forms make their way to the surface and to the branches. Here the 

 winged form develops and flying to new quarters founds other colonies, thus 

 spreading the pest. These branch forms are the most numerous from 

 April to July. About midsummer most of these make their way to the 

 ground and to the roots. Usually a few specimens remain on the leaves 

 throughout the summer and autumn and even through the winter. Our 

 correspondent in Niagara county wrote us November 24, that although it 

 had frozen hard twice, the aphids were as lively as ever on the branches. 

 These individuals which thus hibernate upon the branches with those 

 which come from the ground form the nucleus for the early spring broods. 



This pest is often accompanied by a small yellow ant which has been 

 seen transporting the aphids to places of safety. It is believed that the 

 distribution of the root forms is thus facilitated by the ants, and they may 

 also aid in getting the aphids to the surface in the spring. The aphids 

 repay the ants for their assistance by secreting a sweet liquid called honey 

 dew upon which the ants feed. 



The root forms mostly congregate on the teuderest roots, but some are 

 to be found on all parts of the root system. Many of them still cling to 

 the roots when the trees are dug up, and they are thus often transported 

 great distances on nursery stock. The pest then readily acclimates itself 

 to its new home and soon spreads throughout whole nurseries or orchards. 



Above ground the insects attack the swelling buds in the spring, and 

 later their increase in numbers crowd them onto the twigs and leaves. As 

 each little aphis begins to suck the sap as soon as it leaves the body of the 

 mother, the result of so many hundreds of these little pumps working 

 almost continuously upon both r(jots and branches must be a speedy check 

 to the growth of tlie tree. 



Methods of preceuhn<} the rovages ond sjn'eful of this />c.s/. ^ If this 

 pest once gets a good foothold in a nursery or young orchard, it will prove 

 a difficult insect to fight. Those individuals that infest the branches are 

 easily reached and have been found to succumb readily to either kerosene 

 emulsion or a strong decoction of tobacco.* The emulsion should be 



*T() make the emulsion, thorougtily dissolve '2 pouiifl of hard or soft soJip in 1 guDon boiling water. 

 While this solution is still ver.v hot. add 'i gallous kerosene and (luickly begin to agitate the whole mass 

 through a syringe or force pump, drawing the liquid into the pnnip, and forcing it back into the dish. 

 Continue this for live minutes or until the wli<ile mass ae^unies a creamy color and consistency which 

 will adhere to the sides of the vessel, and not glide off like oil. It may now be readily diluted wiihcold 

 rain water, or the whf)le mass be allowed to cool when it hasa serni-solid form, not unlike loppered milk. 

 This stock, if covered and placed id a cof»l dark place will keep for a long time, in making a dilution 

 from this cold emulsion, it is necessary to dissolve the amount re(iuired in three or four parts of boiling 

 wat<;r, after which cold rain water may be added in the recjuired (inantities. 



The t'lbacco decoction is made by steeping 5 pounds of tobacco Hte/ns in ^ gallons of water for ;! hours; 

 then strain and <lilute with enough water to make 7 gallons. The decoction is now roaily for spraying 

 without further dilution. . 



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