232 Insect Pests. 



trees, such as the plum and the pear ; the Pear Leaf Blister Mite 

 (E. pyri, Scheuten) being very common here, in America, and at the 

 Cape. The gall mite of the currant, like all the rest of the family, 

 is very small. 



The disease caused by it has been known in England and Scotland 

 for a long time past, and appears to have been noticed in the neigh- 

 bourhood of Maidstone quite seventy years ago. At that time it was 

 not known what caused the buds to swell, nor \vas it apparently 

 considered of much importance. It did a good deal of damage in 

 1849-1850 in Scotland and probably earlier, but the first authentic 

 record appeared in 1869 (4), when the infestation was prevalent in 

 Yorkshire, and Professor Westwood referred to the cause of the 

 disease as "a peculiar species of acarus " (4). 



It is only in the last twenty years the attack has caused serious 

 losses, but it has now spread to such an extent that few plantations 

 are free from infestation in this country and no variety that has been 

 grown any length of time appears to be immune. 



The infested buds, which contain thousands of mites, swell to an 

 abnormal size, and though they may eventually open, never do much 

 good and seldom give any fruit of value. None of the supposed 

 remedies are of any value. In one plantation a certain treatment 

 will lessen infestation, while another grower will find that it is a 

 complete failure. 



DESCRIPTION or THE DISEASE. 



The appearance of the buds when infested with the Currant Mite 

 can be seen in Fig. 175. 



The abnormal growth is due to the mites biting the tissues of the 

 buds. A bush badly diseased will be covered with swollen buds, 

 but when first attacked it is noticeable that sometimes the terminal 

 buds are chiefly infested, and sometimes the basal buds only show 

 signs of disease. In other cases both the terminal and basal buds 

 are free from infestation. The difference between normal and 

 infested buds is usually well marked ; the former, as a rule, are conical 

 and look clean and healthy ; while the latter, presenting a somewhat 

 mealy and bloated appearance, are more or less globular in shape 

 (Fig. 175). 



The buds attacked do not always burst open, but they turn brown 

 during the summer. These dead dried buds will remain on the 

 bushes a long time. On opening a diseased bud it will be found that 

 the parts within are distorted and pale in colour, owing to the 

 extraction of the juices by the mites, whose presence will only be 



