CORNELL UNIVERSITY EXPERIMENT STATION BULLETINS. 319 



drawn to the same scale, using compensation ocular No. 6 and objective 

 4mm, Zeiss, with aid of camera lucida. The micrometer scale of this 

 combination is also projected by the side of the figure. 



GEO. F. ATKINSON. 

 THE BLACK PEACH APHIS -^p/iis persiccc-niger. 



Order Heviiptera: family Aphididce~ 



A small brownish-black plant louse often appearing in great numbers upon the leaves, twigs, and roots 

 of young peach trees, frequently dwarfing and often causing the death of the tree. 



The object of this article is to call the attention of peach-growers to the 

 fact that a very serious insect pest is being introducod into our state upon 

 nursery stock purchased in other states. A correspondent in Niagara 

 county has introduced the pest into his orchard of twenty acres by filling 

 in the places where trees had died with infested trees received last spring 

 from a nursery in Delaware. A few infested trees which were left over 

 were trenched near some pits just planted; the pest soon found its way to 

 the young seedlings, and by midsummer nearly every seedling had suc- 

 cumbed to the attacks of the aphids. So. far as we know this is the first 

 instance of the occurrence of this insect in our state, but probably other 

 growers have suffered previously more or less in other localities without 

 knowing the cause. 



The insect is very common throughout the whole of the great peach- 

 growing districts of New Jersey, Delaware, Maryland, and Virginia. 

 Growers there say it is more to be dreaded than the borer ( Sannina 

 exitiosa), and in destructiveness it ranks next to the fearful mysterious 

 disease of peach yellows. Trees less than three years old suffer the most. 

 In 1890, nearly 100,000 in a single nursery in one of these states were 

 killed in two or three weeks' time, while many other large nurseries were 

 either entirely destroyed or very badly affected, and many orchardists 

 were compelled to replant hundreds of trees. Nurserymen and those who 

 are starting peach orchards, can thus see what fearful havoc may result 

 if this pest is once introduced among their trees. 



Indications of the presence of the pest. — As the pest often confines 

 its attacks almost entirely to the roots of the trees, its deadly work fre- 

 quently appears when there is nothing to indicate the existence of an 

 insect as its cause. A stunting or dwarfing of the young trees is one of 

 the most marked symptoms of the presence of the pest. Sometimes 

 three or four year old trees are but little larger than when first set. The 

 foliage of such trees presents a yellowish-green sickly appearance. 

 Rarely a tree after languishing a year or two recovers and makes a good 

 tree. Under favorable conditions the insect may appear in great numbers 

 on the tree above ground and its growth be nipped while yet in the bud; 

 the growing shoots dry up and the young tree soon dies. 



Its past history. — This insect has been known to the peach-growers of 

 the Atlantic states for more than a quarter of a century. From 1800 to 

 1875 it was particularly destructive to Maryland. In 1874 it is first 

 recorded as appearing above ground in destructive numbers. While 

 investigating the peach yellows in 1887, Mr, E. F. Smith came across the 

 insects upon the roots of the trees; and as yellows had by some been 

 attributed to this aphis, Mr. Smith made many observations on the pest, 

 from which we get most of our knowledge of its life history and habits. The 

 severe outbreak of 1890 has already been noted. Two or three years 



