14 DEPARTMENT OF AGRICULTURE. 



into new activity. As regards irrigated districts, it may be said that up to aud 

 including any activity which may be induced by the last irrigation during the grow- 

 ing season, no active blight inay be left. Infection that has apparently dried up may 

 be left, subject to the approval of the Inspector, and on the distinct understanding 

 that should it once more become active it must be removed without delay. In non- 

 irrigated districts it may be possible to allow rather more latitude as to the time 

 when infections may be" considered past spreading. While it may under certain 

 conditions prove economical to leave the blight for a time, it must be understood 

 that this is not a safe practice, and can only be permitted when the grower has the 

 situation well in hand. The stringency of the regulations is not directed towards 

 compelling a grower for his own good, but as a protection to neighbouring ore-bar. 

 As long as actively growing trees have blight exudate in their vicinity and insect 

 pests are present, it is possible for such trees to be infected, thus causing loss to a 

 grower in spite of every care on his part. In some varieties of apples e.g.. Spitzen- 

 berg, Wagener. and Crabs and in many varieties of pears, blight may continue to 

 work as long as the sap flows. In his own interest it would be better for the grower 

 to endeavour to stop the loss of tissue by proper cutting. If, however, the season 

 is advanced, and with a knowledge of all the circumstances, such as the condition 

 of the nearest orchards, the number and kind of insect pests, etc.. the Inspector does 

 not consider that the orchards of others are endangered, it may be permissible to 

 allow the disease to run its own course, provided that a thorough clean-up is made 

 during the dormant season, 



CBOWX-GALL (Pfscudomonas tumefacieM). 



This disease attacks a large variety of plants, including most of our tree and 

 bush fruits, and is transmissible from one to the other ; e.g.. from raspberry to peach. 

 It consists of a swelling or gall, usually on the roots or at the crown of the plant. 

 although it may also occur on parts well above ground, especially in the blackberry. 

 On the apple, in addition to the typical gall, an abnormal condition known as " hairy 

 root " may be found. This is due to an excessive formation of branch roots, of a 

 somewhat fleshy character, from the infected main root or crown. Hairy root " 

 is due to the same parasite as the typical gall, but may or may not be associated 

 with it in the same plant. The galls themselves are of two types, a soft form which 

 rots away each year, and generally grows again at or near the edge of the old 

 wound, and a hard woody form which may persist for many years. Peculiar excre- 

 scences occasionally seen on the limbs of apple-trees are probably due to the same 

 disease, infection having been produced by insects. 



On the apple the disease is chiefly serious on nursery stock, plants at this stage 

 being apparently more susceptible, and the wounds made in grafting and budding 

 affording a better opportunity for infection. The extent to which an affected tree 

 is injured is a somewhat disputed point. There is no doubt, however, that a galled 

 young plant has a much poorer chance of developing into a vigorous tree than has 

 one free from the disease, while if the galls are cut off the root system is liable to 

 be so much injured as to seriously check the growth of the tree. It is, however, 

 true that a tree may outgrow the infection entirely, and that an established tree may 

 have a certain amount of galls on it without showing any ill effects. Large galls. 

 however, especially around the crown, interfere with sap-conduction, and also offer 

 favourable opportunities for the entrance of other diseases, particularly fire-blight, 

 known to be infected should not be used for growing nursery 

 stock. As little opportunity as possible should be given for galls to decay in the 

 soil, since by this means the soil becomes infected. Affected stock should not be 

 planted out. but destroyed. On older and apparently thrifty trees galls may be left 

 alone unless exposed to fire-blight infection. In such a case they should be cut out 

 completely, an inch or more beyond the edge of the gall, and the wound disinfected 

 and painted over. 



