FRUIT RESEARCH

Nelson Evening Mail, Volume 80, 9 June 1945, Page 7

FRUIT RESEARCH

YEAR'S WORK AT CAWTHRON INSTITUTE VITAMIN-C IN STURMER APPLES

That, of the main varieties of apples grown in New Zealand, the Sturmer is by far the most prolific in vitamin-C, the anti-scorbutic vitamin, is confirmed by additional experiments carried out by the Cawthron Institute. Its programme of fruit research for the past year has also included tests of the vitamin-C content of i apple skins, and of jams, further investigation of magnesium deficiency in apples, experiments with apple stocks in relation to fruit j yields and a survey of various aspects of the raspberry industry in Nelson. Eleven phases of the are | summarised in the following annual re-; port:— (1) Magnesium Deficiency in Apples | Observations have been continued on i the apple trees at Tasman and Braeburn which were treated with various magnesium-containing compounds in the 1939-40 and 1940 41 seasons. At both centres Cox’s Orange and Sturmer trees steadily improved in condition for several seasons, those trees treated in both years being better. It has now become apparent that the effectiveness of the various compounds used j (dolomite, magnesium carbonate and j magnesium sulphate) has not been the lame, although the rate of application as magnesium element was identical. Dolomite, especially where applied at 121 b per tree either in one season, or in two seasons at 61b per application, has given consistently more lasting benefit than magnesium carbonate and . more especially than magnesium sul- ■ phate. During the last two seasons, j although some defoliation occurred on Cox’s Orange, the ailment has been ] under con’rol to a degree sufficient to ‘ satisfactorily develop the crop. Un- 1 treated trees have been in very poor, condition and stand in marked contrast in the orchards to the neighbouring; plots of treated trees. I In each season samples of leaf blades. have been obtained from the various | areas and on chemica 1 analysis have shown increased magnesium contents for material from treated trees. (2) Vitamin-C Content of Apples In 1 ! the 1943-44 season samples of apple fruits were obtained from a number of orchards at the time of harvesting the different varieties. Unfortunately in some cases several days elapsed before they could be analysed so that although relatively high vitamin-C contents were found for varieties which had shown low vitamin-C contents in a previous season after commercial storage, the figures were not] necessarily as high as might have been ' obtained had the analyses been made closer Jo the time of picking of the fruits

Expressed in milligrams of vita-min-C per 100 gm of whole fruit ihe following figures were obtained: Gravenstein 7, Cox’s Orange 7, Jonathan 11, Cleopatra 10, Delicious 12, Dougherty 12, Sturmer 29. None of the other varieties approaches Sturmer as a good supplier of this vitamin.

Further work included the monthly examination of frui. held under what approximated to- orchard storage conditions The first analyses were made at the end of May and were continued until the end of September for most of the varieties. Separations were made of flesh and skin in most cases also. Typical figures, expressed in milligrams of vitamin-C per lOOgm of fresh material on the two dates mentioned were respectively, Sturmer, whole fruit 23 and 18, flesh 18 and 16; Granny Smith, whole fruit 8 and 4.5, flesh 5 and 3: Delicious, whole fruit 12 and 12, flesh 8 and 1.5. Statesman was outstanding for the vitamin-C content of its skin, the early samplings giving about 90mg per lOOgm of fresh skin. Besides the vitamin-C content the titratable acidity was estimated at each sampling. This fell rapidly at first and then more slowly in a manner similar to that shown by the changes in vita-min-C content. (3) Vitamin-C in Fortified Jams A number of jams, fortified with rose-hip powder or with pure ascorbic acid, were prepared by a local manufacturer and have been held for* up to six ‘months under ordinary laboratory conditions to see what changes might occur in the vitamin-C content. Jams fortified with rose-hip powder and containing originally 40 to 50mg vitamin-C per lOOgm of jam lost on an average approximately 16 per cent of their vitamin. C content in three months but lost very little after a further three months storage. When pure ascorbic acid was used to bring up the content to about 500 mg per lOOgm of jam the losses after three months averaged slightly less than 6 per cent.; data for the six-months period are not yet available’. (4) Die-back in Apples During recent years apple trees in certain orchards throughout the district, but more particularly on the Mou tere Hills, have shown marked symptoms of “die-back” which eventually causes the death of several branches or even the whole tree. In early stages of “die-back” one or two branches may fail in the early spring to develop blossoms and foliage in a normal manner. Later'in the season, a fair recovery of foliage may be found but yields of fruit on affected branches are adversely affected. In succeeding years the effect on the tree is .more serious and several branches may be killed. The trouble is found in both good and poor orchards, although it is generally more drastic in its effect on poor thin soils. A preliminary survey of “die-

back” in several orchards has been made and it is hoped to continue both field and laboratory examinations during the 1945 46 season. (5) Apple Stock Experiments at Anncs. brook Orchard The past season has shown again the superiority of Double Vigour stock (French Crab seedling vegetatively propagated) over Northern Spy stock for the Statesman variety on the Annesbrook soil. This block was planted in 1931, yields being recorded for the first time in 1938. In the earlier years of bearing, the Northern Spy stock showed a slight advantage in higher yield of the Statesman trees but during the last three years, the trees of the more vigorous stock have outstripped easily the trees on the Northern Spy stock. In the 1943-44 season the yield of trees on the Double Vigour stock was approximately 1 bushel per tree greater than those on the Northern Spy stock. The following table shows the yields from the two stocks over the last four years:

Yields were recorded lor the first time from the Cox’s Orange and Jonathan stock blocks which were planted in 1934 and 1935. In these stock experiments a comparison is being made of Northern Spy stock against a locallyproduced vegetatively propagated seedling stock and Northern Spy versus three East 'Mailing stocks Nos. 1, 13 and 15. In the case of both Cox’s Orange and Jonathan, the more vigorous seedling stock is already giving a higher yield than the Northern Spy stock by as much as J bushel per tree. In regard to the East Mailing stocks, which were planted together with their control Northern Spy stock, a year later, the yield from East Mailing No. 1 stock is a little higher on both varieties than Northern Spy with East Mailing Nos. 13 and 15 stocks well behind. (6) Annesbrook Orchard The 1943-44 season was another very favourable one at the Annesbrook orchard. Very # little trouble from disease ior insect attack was experienced. The fruit was of good size and colour, facilitating greatly the grading and packing of the crop. The pear crop was poor, but the apple crop was- the heaviest so far obtained at the Annesbrook orchard. Jonathan, Statesman, Cox’s Orange, Sturmer and Dougherty varieties all did particularly well. The yield from the 10£ acres of bearing orchard was 5150 bushel cases, being only 83 cases below the high yield of the previous year. Comparing the costs of production in the 1943-44 season with those of the previous year, an increase of 2d per case was found.

(7) Survey of Raspberry Soils Typical raspberry soils located in all the important centres of raspberry culture in the Nelson district were examined botll in the field and in the laboratory. The best gardens .were invariably associated with sandy loams of good depth and free drainage. Where drainage was impeded gardens frequently showed signs of deterioration. : Raspberries on heavier types of soil, e.g., silt loams, were inferior to those on sandy loams. The best gardens had yields of 3 tons of raspberries per acre and many gardens, particularly in the Tadmor Valley, averaged over 2 tons of raspberries per acre.

All the soils used for raspberries were high in available phosphate, but were low to very low in available potash. Considerable variation in the pH value of the soils was found. The average pH' for 12 typical soils was 5.9 but values as low as 5.3 were found. The chemical analyses suggest that potassic manures in the fertiliser mixture could be increased to advantage and in some gardens light dressings of ground limestone at the rate of j ton per acre should be applied. (8) Disease Survey of Raspberries At the request of the Nelson Raspberry Marketing Committee a survey of diseases affecting raspberries in the Tadmor Valley was carried out. One or two gardens as the result of flooding and wet soil conditions had suffered b%dly from root-rot fungi, particularly Rosellinia and the Silver-leaf fungus. In other gardens only isolated plants were affected. Fructifications of the cane wilt fungus were also present as also, where soil conditions were wet. were those of the fungus Nectria. With few exceptions the gardens were in a healthy state. (9) Bulletin on Raspberry Culture With a view to the extension of raspberry culture in the Nelson district, help was given to the Nelson Raspberry Marketing Committee in compiling a bulletin dealing with the culture of raspberries in the Nelson district. The technical sections Of the bulletin were written by officers of the Cawthron Institute*. (10) Brown Rot and Black Spot i The usual notification service in connection with the maturity of brown rot | and black spot ascospores has been j maintained for the benefit of orchardI ists in the Nelson district. (11) Codlin-Moth Parasites Three parasites were imported from North America in 1942. One of these. Ephialtes Caudatus. a larval j parasite was reared and liberated ! in abandoned orchards in 1943. Despite careful inspections during i the 1944-45 season in two orchards I where liberations had been made, no trace of the parasite was found. During the past season, another larval parasite Acnoplex carpocapsas. was reared to small numbers and liberated. .

Season Northern Spy Double Vigour stock 'lb per tree lb per tree 116 1942 116 134 1943 .. 126 148 1944 .. 167 209