22 STATE HORTICULTURAL SOCIETY. 



by using wrappers around the base of the tree as a protection against 

 borers and rabbits. Bat whatever may be the cause of their presence 

 above the ground, the result is the same, namely : to cause an abnor- 

 mal growth of the infested portion resulting in the formation of a rough 

 and pitted surface, and at times cause the death of the limb at the 

 point infested. However, this injury is so slight in this State that it is 

 insignificant in comparison with that found in the northern and eastern 

 states, and especially in Europe, where apple trees are frequently 

 killed outright by this aerial form. 



The presence of the root inhabiting form is readily detected by 

 removing the earth from the roots near the trunk of the infested tree. 

 The appearance of a bluish-white cottony or mildew looking substance^ 

 or of knotty and distorted roots will indicate its presence. It is this root 

 or subterranean form that causes so much damage to the apple orchards 

 in the southern half of Missouri, and to apple nursery stock through- 

 out the State. The infested apple tree appears sickly ; it does not 

 grow as it should ; its leaves are less numerous and they have more of 

 a pale green or yellowish color than is natural: and finally the tree 

 dies outright or is blown over with the- first slight wind. Such are the 

 outward indications that a tree is badly infested with this pest. Some- 

 times the tree blows over with a heavy wind without showing these 

 outward appearances in so marked a degree, but one soon becomes 

 familiar with the appearance of infested trees and can readily locate 

 them before they are past recovery. In orchards, it appears that the 

 great bulk of the damage from this pest comes directly from the fact 

 that the trees blow over so easily, the roots breaking off close to the 

 trunk. Of course this is due to the fact that the roots have decayed ; 

 and I am fully convinced from actual observation that ninety-five per 

 cent of the cases of so-called "root-rot" in apple trees in this State is 

 in reality the result of the attack of the wooly-aphis. In nursery stock,, 

 the damage comes directly from the inability to sell badly infested 

 trees, and not from the death of the trees themselves. 



The wooly-aphis sucking the juices from the roots of the apple 

 tree causes an abnormal growth of the attacked portion of the roots 

 resulting in the formation of gall-like swellings or excrescences. These 

 swellings are usually irregular and knotty in appearance and sometimes 

 attain considerable size, while that portion of the roots between the 

 excrescences is frequently undeveloped. 



The wooly-aphis will be found in large numbers and in clusters 

 over the surface of the swellings, and especially between them in the 

 numerous crevices that the larger excrescences contain. The roots 

 thus attacked, distorted and swollen soon begin to decompose ; sap- 



