WAR ON PLANT DISEASE

Manawatu Times, Volume LIV, Issue 6901, 6 May 1929, Page 10

WAR ON PLANT DISEASE

The Mode of Attack

EEMABKABLE GLASSHOUSES

NEW EXTORT POSSIBILITIES

Glasshouses of remarkable construe tion, and provided with most elaborate heating., watering and isolation systems form part of the equipment of the plant research officers at Palmerston North in the investigation of the problems of plant diseases. Within about a year of the centralisation of this work in the region of Massey Agricultural College, much has bc-en done. In most cases, however, research along any one lino is ncccssarilv slow, involving .work spread ove/scveral growing seasons before results sufficiently reliable fo be broadcast arc secured. The manner in which the department successfully combatted disease among the cereal crops of Canterbury is history, and there will shortly be "published'the results of experiments into the effects of sowing lucerne seed together with some manures.

One of the most important investigations now in hand, and promising something of considerable commercial importance to the Dominion, affects the growing of peas in this country. Research workers say the posibsilitics of seed-growing in general in New Zealand arc tremendous, if only disease can be eliminated. An' officer of the department., discussing, the question recently, commented upon our substantial importation of clover, cocksfoot and field pea seed.

London Pea Market.

There was a huge market in London tor peas as stock fodder and New Zealand could grow them far better than England were it not for the ravages of collar rot. If the average farmer could be reasonably sure of a 40-bushel crop there would be little doubt ot pea-growing becoming a big thing in the Dominion. He could then contract to supply merchants for export. At present lie deemed himself fortunate to secure a 20-bu.:hcl crop; there was no stabilisation of the market, and therefore little opportunity to develop tiadc under such conditions. Quite apart from the selling value of peas as a field crop, there was their value as a soil-enrieheniug rotational crop. That was iceogniscd the world over, for in every agricultural country of consequence the problem of collar rot was the subject of research. As yet little had been achieved, but research was continuing along with trials of seed . disinfecting and the production of nucleus lines of disease-free seed.

Dieases in Potatoes,

Latest of the work conducted with respect to. disease in potatoes was the growing of about 100 selections from the most promising varieties in New Zealand., As the crop grew diseased pJnnts'wcrc ‘roguod” out and destroyed, leaving Aicleus lines apparently disease-free. These, in turn, would bo again sown next season under the same conditions, in Palmerston North and Canterbury.

There has also been secured a large number of special selections of English, Scottish and Irish potatoes ,supposedly. free from disease. ■ This seed lias been put in at Palmerston North late in the present season, but it was hoped to secure from them enough seed to continue the best strains next season. The principal trouble in potato culture appeared to be virus diseases where contagion was transmitted by aphides. No direct organism had yet been found, although the medium, whatever it was, was so minute that it could h ;: filtered through the finest bacteria filter, a filter so fine that it would remove from a solution any. particles observable through the highest possible magnication.

Tomatoes and Swedes.

was typical of such diseases that they caused a serious degeneration of the plant and the ‘running out” of varieties. 'Without doubt there had been a steady deterioration of the finality of table potatoes in New Zealand, and the present aim, apart from research work, was to produce, through the certification of crops method, a better class of tuber.

The study of virus diseases in tomatoes had not as vet been given such wide study, amt the Palmerston North station was waiting upon the results of further investigation into similar ftouble with potatoes. In the ease of dry rot in swedes and turnips, the treatment of seed had not. proved an absolutely successful method of control. Hie agent of disease was known to be an inferior organism which could be effectually killed in the laboratory, but not in the field. Here, again a crop under cultivation was being carefully watched and all diseased plants pulled out and destroyed as soon as infection y.as noted, with the object of developing a line of disease-resistant seed. r l hat appeared to be the only way out it seed-disinfecting methods could not be made successful, for at present nearly all the imported seed was infected with dry rot. Moreover, if, was seldom less than two years old, and therefore somewhat deteriorated, and again, the New Zealand grown seed was definitely superior. All those lines of research were intimately bound up with increased production, for if such crops could be more successfully grown, the carrying capacity of farms through the winter months would be greatly increased.

Exactitude of tests. Tup-dressing had vastly increased pasture and crop growth in the favour-

cd seasons of the year, but the farmer was left confronted with the problem cf how to carry through tho winter a larger proportion of his summer stock and thus Lett or his average rctuhns. The most spectacular feature of the plant research work at Palmerston ■ North is the growing in glasshouses and other specially constructed enclosures of various farm crops to ascertain just how they become infected by disease, anil how they behave under different conditions when completely isolated from all outside conditions. One structure consists of a framework with, double enclosures of brouzo gauze of the very finest mesh—far too small to admit the most minute insect known. The research workers whose concern this department is goes into an antechamber and changes into auothcr suit of overalls before finally entering the ii nor enclosure to examine the plants. Thus is every precaution against, the entry of insects taken, for tho admission of even one might spread disease and destroy the whole work of many months. Similar tests arc carried out in spe-sially-const nietcil glasshouses with jealously guarded entrance doors. Inside tho main glasshouses arc smaller cases of glass. Into these lead close-ly-fitted water pipes for the sprinkling of the soil without the risks which