240 [ DISEASES OF THE PEAR TREE 



ANIMALS. The rootlets of the pear-tree growing in 

 stiff soils, insufficiently drained, sometimes develop small 

 irregular nodules or galls within which is found the eel- 

 worm (Heterodera radicicola Mull). The injury caused to 

 the roots by these eel-worms, particularly where the land 

 besides being too moist, has been also heavily manured 

 for the cultivation of vegetables, results in a state of 

 general malnutrition with sickly twigs which easily 

 die off during the winter. In such cases the soil should 

 be dug deeply and allowed to dry, or sown with crops 

 which do not require watering. Pear trees grafted on 

 the wild pear or on pear-seedlings develop nodules 

 on the roots, usually as large as a walnut, but occasionally 

 much larger. These nodules are due to an abnormal 

 or uneven process of nutrition and are probably not 

 due to any parasitic action. 



The stem and the roots of young pears, at a depth 

 of 10 to 15 c.m. below the surface of the ground, are 

 sometimes gnawed off and deeply injured by the grub 

 of Geotrupes laevigatus F. This grub, about 5 c.m. in 

 length, is grey- coloured, fat, and is always found curved 

 upon itself like a horse-shoe. It lives on the sap of the 

 young trees and in spring comes out of the ground as 

 a large black beetle. Its Maltese name is b^lkauuar 

 and the havoc caused by the grub as well as by the 

 beetle itself in its early life, to rose plants etc. is well 

 known, but it attacks also the pear, the apple, the quince, 

 the almond, the plum and other fruit trees. The young 

 tree attacked by it of course dies, if the stem has been 

 completely gnawed off, but is always so deeply injured 

 even when the damage is only partial, that it is better 

 to replace the young tree. 



There are two Acari or mites affecting the pear 

 tree. The one more frequently met with is Phytoptus 

 Piri Sor., which produces small protuberances or papillae 

 on both sides of the leaf (Italian vaiuolo}. These 

 papillae at first are yellowish or reddish, and then turn 



