DISEASES IN PLANTS

Hokitika Guardian, 14 September 1928, Page 4

DISEASES IN PLANTS

RESEARCH WORK. PROGRESS OF IMPORTANT. INVESTIGATIONS. Following on tlio declaration by the president of tho British Association concerning the importance of science to industry comes confirmation of the increasingly valuable part it is playing in Now Zealand, A Wellington “Post” representative lmd a chat with Dr Cunningham, in charge of tho mycoiogical 'laboratory of tho Plant Research Station now operating in Palmerston North, and that gentleman gave some illuminating facts demonstrating tho value of science to primary production in the Dominion. Indeed, it would not seem over-optimis-tic to state that already tho deathknell has been sounded for many oi the,crop diseases which have cost this Dominion millions of pounds annually.

“One of our major problems,” said l)r Cuijniiighnm, “is clubroot in swedes. Our investigations are being carried out along threo linos—firstly, whether the disease is seed-home; secondly, how long the disease will last in tlio ground; and, thirdly, whether weeds related to sWedes, such as wild turnip, shepherd’s purse and tho like, act as hosts for tho disease. If the disease is seed-borne, wo will bo able to work out ii method of seed treatment tliat will ensure that in virgin land the resultant crop will ho diseasefree and the land will remain uninfected.

As regards the length of time the disease wil last in tho ground, Dr Cunningham stated that the investigations were of an exceedingly complicated nature and will extend over seven years. Crop rotations and crop combinations and maiiurial effects were all being taken into account. Tlio question of whether tlio disease was seed-borne or not will be decided this year.

COLLAR ROT IN PEAS. Although a major problem for inves tigation, collar rot in peas. Dr Cun ninghnm explained, did not have such an important place in the list of dis eases affecting the wealth that was being derived from tho land, in that pea-growing was not a very extensive industry. Investigations had proved that tho disease was carried in th seed, and his staff was now devisin',' a method of seed' treatment with th view to its elimination. It was not known whether the organism persisted in the soil, and a series of experiment! to decide this point were being undertaken this year. If it is found that tho trouble does persist in the ground a method of treatment will have tr he worked out, at least to shorten the life of the germ.

“At the present time,” he added “ we are preparing to raise hulk line! cf pedigree disease-free pea seed ii Palmerston North. This seed wiii In distributed later to selected farmers who will grow it under Departmental supervision in various parts ol th, Dominion.

INSECTS UPSET EXPERIMENTS. Dry rot in swedes, which caused losses in a year amounting to a million pounds at least, it was explained, was a seed-borne disease, and was not carried in the, soil. The problem of its control hinged on the working out of an efficient method of seed treatment. That had keen done in the laboratory but in the field 'it bad been foiilul that insects, man himsef, mid small an mills upset the calculations of tlio investigators in that racy carried the rot organisms on their feet from, crop t crop. This year the station is carrying out aii elaborate series of experiments umlhr'insect-proof cages designed to pro#: (1) That diseased lines of seed will give rise to diseased crops; (2) that clean seed will result in a disease-free crop; and (3) that treated diseased seed will jlroduoe clean roots. GETTING RID OF SMUT.

Cereal crop surveys for the past five years have shown that the two major diseases causing losses were smut and take-all. Experiments in smut control have proceeded to such an extent that it is now possible on a commercial scale to produce large areas of smut-free cereals. For example, tlio whole of the malting barley grown in Canterbury last season was smut free, as a result of the work of the department.

Oat smut, which hitherto caused an annual loss of between £OO,OOO and £IOO,OOO in Canterbury and Otago alone, has by improved methods been reduced to a mere trace in' ii small number of crops. Experiments were now being concentrated on take-all, with a 'view of determining whether it was seed-borne, and if so whether treatment will eliminate the disease. Investigations were also being made to determine whether it persisted in the soil. Strijie in barley and wheat was also tb be studied this year. GOOD NEWS FOR POTATO GROWERS.

Speaking about potatoes, Hr Cunningham stated that he had every hope that the Dominion yield would soon he brought ii]i to what it used to he. At tlm present time it had depreciated more than TO per cent. The four major diseases attacking potatoes and reducing the annual yield were: (1) Corticium disease, which causes the misses in the rows by attacking the young shoots as they made their appearance; (2) fusarial wilts, responsible for killing the growing plant ill the field; (3) early blight, which caused general stunting; (4) virus disease responsible for tile general reduction in yield. The last-named disease had reduced the yield in New Zealand from eight tons to three tons per acre. Corticium disease was carried on the surface of tile tuber, so experiments in connection with its control were in the nature of chemical steeps. The other three diseases were carried in tlie tubers, and the only way of dealing with them was by the selection of disease-free seed. This year tho initial work of control was to be put into operation. All commercial varieties are to be grown, and the lest plants will be selected and propoguted from in bulk. Kaeh year this principle of sole, lion is to bo further carried on until the diseases have been completely eliminated.

Certain factors interfered with the work. For instance, early blight was carried by tho air from plant to plant.

while the virus disease was carried b.v insects. It was necessary in dealing with early blight to spray consistently. Virus-free patutr.es would only remain virus-free if insects were excluded from

access to the crop or if they wore grown in an area where those particular insect-carriers were not present. Part of the work in hand bv the Research Station was to ascertain regions in New Zealand where those insects (aphides were the chief carriers) were not present.