CHAPTER XXI 

 INSECTS (continued) 

 CURRANT GALL MITE (Reports, II, 7; XIV, 69) 



THE Black Currant Gall Mite, or Big Bud (Eriophyes ribis, 

 Nalepa), is an insect which is very prevalent, and one which 

 constitutes a serious drawback to the cultivation of black 

 currants in this country. 



The mites enter the buds during the summer, and from that 

 time onwards they rapidly increase, so that, by the commence- 

 ment of winter, the interior of the buds are swarming with them. 

 As many as 3000 have been counted in a moderate -sized bud. 

 Before June many of the mites leave the old buds, and lay their 

 eggs on the newly-formed shoots, between the leaf stalk and the 

 young buds. Before the end of July some of them have entered 

 the young buds, and by the end of September many of these 

 latter show the undoubted signs of infestation, being rounded 

 and much swollen (Fig. 22). The mite then remains in the 

 bud, which continues to swell, and it survives the cold of winter, 

 without any evil effect beyond a certain amount of sluggishness, 

 which disappears as soon as the temperature rises. The buds 

 which are infested, though they may expand, do not develop, 

 and as the season progresses, they dry up and die. Whether 

 the majority of the mites leave them before then, or not, is 

 uncertain, but the dead buds always contain a mass of dead 

 mites. 



Where this insect originated is not known, but records of 

 its existence in Scotland date back to 1850. Any attack on 

 it is beset with difficulties. Its minute size renders transporta- 

 tion by the action of the wind and other agencies a matter of 

 great ease : its period of activity, while migrating from bud to 

 bud, is a very extended one, and, apparently, covers nearly the 

 whole time during which the bushes are in leaf; and while 

 enclosed in the bud it is thoroughly protected from the action 

 of most insecticides, the currant bud being especially compact 

 and close-knitted in structure. 



