Galls 



[N.B. — Similar enlarged growths formed by fungi 

 have already been referred to, e.g. azalea 

 gall, club-root, wart disease of potato, leaf- 

 curl of peach, crown gaU. In these no 

 insect is to be found.] 

 The principal galls calling for mention as needing 

 attention in the garden are big-bud in black currants 

 (due to a mite ; the big-bud of hazel is similar but 

 distinct) ; leaf-bhster gaUs of pear leaves ; rose galls 

 (Robin's pincushion, and the round swellings on 

 rose leaves) ; weevil galls on cabbages and turnips 

 (usually near " coUar " of plant, but not under- 

 ground like club-root, a much more serious pest) ; 

 woolly aphis galls on apple, etc. ; aphis gaUs on 

 poplar leaf-stalks ; Phylloxera galls on vine roots. 



IV. Other Symptoms 



28. Tiny flecks of whitish colour over the whole 

 or a great part of the surface of leaves and flowers : 

 thrips (often called thunder bugs). 



29. Similar discoloration or brown or reddish or 

 even fiery red markings, with a fine web on lower 

 surface : red spider (a mite — ^not an insect). 



30. The presence of excrement or the remains of 

 partially devoured tissues ; e.g. bulb mites leave a 

 dust-like mass in the bulbs they destroy. The mites 

 themselves are like grains of sand in this debris. 



116 



