FIREBLIGHT IN NEW ZEALAND

Dominion, Volume 23, Issue 141, 11 March 1930, Page 17

FIREBLIGHT IN NEW ZEALAND

WIDESPREAD IN NORTH ISLAND HISTORY; OF DISEASE l ; ? v ; .?' ... .“1 ■ ' J It is not generally known that the dreaded fireblight has appeared in orchards throughout the length and, breadth of the North- Island, and indications go to/show that this deadly plant .disease is rather on the increase. In fact, the spread of the fireblight has rapidly grown since its presence was announced in New Zealand in 1919, until now there is scarcely an orchard in the North Island which is immune from it. It is well known that the hawthorn is very susceptible to the fireblight bacteria. Having regard to.the value of hawthorn to dairy farmers and others over certain, areas,, and equally regarding the menace it is in certain parts to prehardists, a Fireblight Aet was passed in 1922. defining orchard areas and giving the authority to declare- the course of procedure to be adopted in regard to hawthorn according to the individual needs of each locality. Where the fireblight is said to be most rampant, in the Waikato and surrounding districts, the farmers are very reluctant .to remove the hawthorn hedges, which undoubtedly form wonderful natural fences, and as the Government can only serve notices requesting that such removal be made—the question of employing men to do the work compulsorily being virtually impossible—the hedges remain, and the farmers themselves directly suffer in the loss of their fruit. Early History of Flreblight. One hundred and thirty-six years ago (1794) a record was made for the first time, of the occurrence of fireblight in New York State, U.S.A., and more than a century has now ’gone by since the announcement of its prevalence in North America, says Mr. R. Waters, of the Biological Laboratory, Wellington, ln>the course of some observations of the disease, which have been published. Bacteria ’ were' certainly known in 1817, though there was no good reason to believe that they were' responsible for fireblight or any other plant disease. Suggestions had been made that they might be causative of animal diseases, but little attention was paid to this matter until 1849,- when Pollander and Davaine asociated bacteria with the condition of orthdox. Twenty-seven years later R. Koch clearly demonstrated that anthrax In animals was due to a specific bacterium, Then comes the first record of the association of bacteria with plant disease, Burrell noting them in fireblighted pear twigs. Thus the Americans have known the fireblight condition for over a century, while for fifty years they have recognised it as a bacterial disease—and still it spreads. In 1909 the disease was reported as more widely spread in Canada than it had ever been before; it was “continually spreading into now territory, causing heavier losses than formerly to the fruitgrowers,” In certain States of the American Union it has rapidly wiped out the pear orchards over extensive areas. In 1911 it was recorded as very destructive in northern parts of Japan. ’ Appearance in New Zealand.

I The announcement of the presence of fireblight in New Zealand in 1919 'caused some sensation, and now the disease is seriously regarded by most growers and associations throughout the Dominion. Erwinia amylovora Burrill, the bacterium responsible for" fireblight condition, wa's isolated first in 1919 from pear twigs grown at Te Papa, near Auckland. In the early part of 1920 fireblighted fruittree specimens were received from widely ; separated points throughout the Auckland' province, and by the end of that year the disease was known ‘to extend from Warkworth in the north, down through the Auckland-Onehunga localities to the ..Waikato-district, about 15 miles to the south of Te Awamutu, and across the Te Aroha-Hamilton vicinities to the fruitgrowing areas of the Bay of Plenty; In 1922 Taranaki was in- . vaded and a single specimen of the disease was discovered in the Wairarapa. In 1923,and 1924 there was no evidence of the disease crossing the larger natural boundaries into new districts, but there is little doubt that in the following summer fireblight had actually passed unobserved into Hawke’s Bay, for in November, , 1926, oozing hold-over cankers (indicating infection of the previous season) were sent in from Havelock North. About the same time infected specimens were received from Palmerston North, and early in 1927 the disease was known to have penetrated as far south as the Hutt Valley. Since then indications show that the disease is slowly increasing in the districts mentioned above.’ Thus, in a period of about nine years fireblight gradually spread southward over the North Island a distance exceeding 300 miles, and now as a necessary safeguard -the whole of the North Island must be treated as an infected area. The South Island, which contains our largest fruitgrowing district, fortunately has shown no trace whatever of the disease,- -. ■< Problem of Hawthorn Hedges. Here, as in America, pears have suffered most; the control of the disease in them is certainly more, difficult than in apples. No apple varieties have yet been proved to be immune to the disease, but some varieties are somewhat more resistant than others. Our primary difficulty in combating the disease in the apple is due not so much to the character of the disease in this species, but rather to. the liability to reinfection from diseased hawthorn,' a factor scarcely met with in North America. Hawthorn is not only abundant in parts of the Auckland and other provinces, but it also takes the disease fairly freely. Thus the abundance °f fireblight hosts in any locality is a means for rapid spread and a hind-rance-to satisfactory control. In Ameri- I ca quince and juneberry appear liable to serious injury, but the stonO-fruits are reported to be rarely affected there.. While, therefore, the pear is our most seriously affected fruit-tree, the orchard industry is more concerned with the effects upon the apple. Owing, however, to the enormous extent of hawthorn hedges in certain of our fruitgrowing districts the control of fireblight in either apples or pears is inseparably connected with the . eradication of hawthorn. ■ „ ' Control of the Disease, The difficulty with fireblight is that there, is no method of treating the trees to prevent infection, or is there any method of combating the disease by spraying or other means other than by -’cutting ■ the infected portions avVay from the tree. The presence of fireblight may bo recognised by a blackening, which generally initially affects the blossoms, and the disease is known in certain parts as “bios-, som-blight.” In the presence of suitable conditions of moisture and temperature the blackening process extends from the immature fruit down through the fruit stalk to the spurs or twigs. In pears it often advances into the branches, or on to the lenders, or even to the trunks. Such rapid progress ; is. fortu-' „ nately, not met,with in. l apples. The disease passes through the tougher bark of old apple trees more slowly than through , that of young trees. Ifi like manner the disease will pass more rapidly through young bark than it will through the older bark of a tree, In pears it has been known to reach the main trunk, killing large trees outright in a single season. Fireblight was the first bacterial plant disease shown to be transmitted by insects, and the patient work of many investigators has resulted- in a most, formidable list of insects concerned in this matter. Many of the insects are present in New Zealand. The disease can. also be conveyed by man himself, states Mr. Waters, and there is no conceivable manner by which fireblight could enter New Zealand from America or Japan except by this means. If, then, the disease leaps any of our ■

natural boundaries where no host plants grow, or if .it passes across Cook Strait, it. is highly probable that man himself will'bd to blame. The publicity that has been given - 'to the danger of transferring infected paterial from one place to another, and the Act,and regulations making it a punishable offence to send Or receive susceptible plants from places Where the disease is declared, will no doubt, have a deterrent effect on the spread of fireblight.