THE PEAR BLIGHT.

Lyttelton Times, Volume CXVI, Issue 14169, 18 September 1906, Page 5

THE PEAR BLIGHT.

CURE BETTER THAN RESTRICTION. At the fruit growers conference in Wellington last week the chairman brought up the question of blights. - The Hawke’s Bay Association, he said, had written to the Minister asking that the importation of Californian peartrees or buds should be prohibited until a remedy for the Californian pear blight had been discovered. The conference passed a resolution urging the Government to make regulations to prevent the introduction of the pests into the colony. Mr J. C. Blackmore, Government pomologist, when seen by a “Lyttelton Times” reporter yesterday, stated that there was no necessity to impose any such restriction. Nothing had so much puzzled scientists as this particular blight for the last twenty or thirty years, but its true nature had at last been discovered, and it was comparatively easy to combat. It was called also twig and fire blight, and might be defined as a contagious bacterial disease of pear, apple, .quince and other pomaoeoue fruit trees, including the mountain ash, service berry, and all the species of cratagus, or hawthorne. The minute microbe which was the cause of the trouble was known to scientists as bacillus amylovorus, and was of very wide distribution throughout the United States. The blight first appeared in spring on the blossoms, the flower cluster turning black and drying up as if killed by frost. The disease also attacked the young fruit, twigs and shoots causing a distinctive blackielh discoloration of the leaves on the attacked twigs. Frequently the disease worked its way down from the twigs through the bark to the larger limbs, or even to the trank,'killing the inner bark and cambian layer of the limbs and trunk as far as it extended. All parts of the tree below the point reached were healthy. Another way in which the blight gained an entrance was through the tips of growing shoots. When trees were not flowering this was the usual means of infection, and especially so if the tree was making rapid growth .of new and soft tissues. The disease would spread with great rapidity through an orchard at blooming time, and this peculiarity had

thrown much light; on the way the minute • microbes travelled _ about. . They lived and multiplied in the nebtar of j the blossoms, whence they, were carried away by bees and other insects. If a few blossoms i were infected, the insects would scatter l the disease from flower to flower, and .- from-tree to tree, until it became an , epidemic in the orchard. The blight • ; microbes lived over_ the winteralong the advancing margin of the blighted, 1 area which separated the living-from ' the dead wood, and when the saps bo-. • gan to move in spring, those that had i lived over winter started anew to es- > tend into new bark, from which, guip 3 was exuded" containing the microbes;. Bees and flies were attracted to this 3 gum, and undoubtedly carried the mi- • crobe to the blossom. From these first I flowers ■ the disease was carried to i others, and also to the young growing > tips, causing twig blight as well. The • treatment might be classed under two ' general heads; firstly,, to put the tree I in a condition to resist blight, or fender s it less liable to disease; secondly, me» 3 thods for exterminating the microbe itl self. The method under the first - head must be towards checking the s growth of the tree,, witholding- the • pruning knife, and abstaining froih.fer- , tilisation, tillage, or irrigation, in order ;• to check wood growth. Tire method i under the second head, and the only i really satisfactory plan of controlling 1 the blight, ■■was to exterminate the mi- - crobe which caused it, but cutting out 3 and burning every particle of blight. , The best time to do this most thorough--1 iy was during autumn, when the foii« » age> was still on the trees-- and. the con- , trast between that on the healthy limbi > was so great that it would be an eas" 1 matter to find allthe blight. 'WhenJ ever careful attention had, been given 5 to. this simple method of procedure, by ’ cutting out the disease, it had been s completely exterminated.. Mr Black--3 more concluded by saying that • one of the most disastrous : plant maladies, and ' one that 1 had baffled all attempts to 'find a 3 satisfactory remedy, • oould be easily ■ and practically dealt with in a simple 5 way, since, a thorough knowledge had • been acquired of the life history of the ’ microbe that caused it.