Nature and Control of Ripe Spot of Apples

New Zealand Journal of Agriculture, Volume 84, Issue 3, 15 March 1952, Page 239

Nature and Control of Ripe Spot of Apples

By

C. E. WOODHEAD,

Pip Fruit Specialist, Department of Agriculture, Levin, and

H. JACKS, Senior Plant Pathologist, Plant Diseases Division, Department of Scientific

and Industrial Research, Auckland

D IPE spot (Neofabraea malicorticis) continues to be responsible for part of the •N annual toll taken of the New Zealand apple crop by disease. As this wastage can be reduced if all apple growers adopt recommended control methods, this article describes the nature and control of ripe spot and includes an account of trials of new fungicides by the Plant Diseases Division of the Department of Scientific and Industrial Research.

RIPE spot is caused by the fungus Neofabraea malicorticis. According to G. G. Taylor and R. M. Brien “the disease is first apparent as a superficial pin-point spot, light to dark brown in colour and slightly depressed. In some instances the spot may be surrounded by a red halo, but this is not a reliable diagnostic feature, as lesions with or without the red halo may be found on the same fruit. Lesions develop slowly, become dark brown to black in colour and more obviously depressed. ...” This later stage of development, as described by Taylor and Brien, is shown in the accompanying illustration. The development of ripe spot is described by Taylor as follows: — Ripe spot, is not an actively growing fungus like black spot or bitter rot and fruit may be heavily infected without showing visible signs of infection. This means that a line of fruit which only appears to be lightly infected at picking time may actually be heavily infected, and for every visible lesion 30 or 40 may develop after several weeks in store. Ripe spot lesions develop slowly and fruit showing infection may be held for several weeks after picking without the spots causing any economic damage (other than unsightly appearance) to the fruits. When the fruit reaches a certain stage of storage maturity the fungus spreads more rapidly and in cool store often provides a point of entry for soft rotting fungi. Control Methods Effect of Fruit Maturity on Development of Ripe Spot Experiments carried out by the Plant Diseases Division have shown that, excluding spraying, the' chief factor controlling the development of ripe spot after infection is the maturity of the fruit. In short, the more mature the fruit is when picked or when it enters the cool store the greater will be the development of the disease. It is possible therefore to control ripe spot to a very considerable extent by early picking, quick dispatch to cool store, and holding the fruit in cool store at the lowest possible temperature consistent with maintaining the variety in good storage condition. In practice, however, the date of picking is governed by labour, weather, and the maturity requirements of the variety as affecting . fruit quality. Further, circumstances beyond the grower’s control, including inadequate local cool storage, may at any time prolong the interval between harvest and cool storage and thus hasten the maturing of the fruit. Spraying Though any procedure that delays fruit maturity also checks development of ripe spot, it does not protect

the fruit against infection. Taylor reported that the evidence of spraying trials indicated that the period of maximum ripe spot infection occurs before the beginning of harvest and that the critical period of ripe Spot control is from mid-January to midFebruary.

Fruit can be protected against infection only by spraying. That this is effective has been. shown by Taylor in trials in which summer Bordeaux sprays reduced visible ripe spot ,at harvesting to as little as 3 per cent., compared with 34 per cent, in fruit that had received sulphur sprays. There is also ample evidence from experiments by Plant Diseases Division that summer Bordeaux sprays are very effective in checking the later development of ripe spot in cool store. In a series of cool store trials the number of Bordeaux-sprayed fruits showing ripe spot ranged from 7 to 16 per cent., compared with 33 to 62 per cent, in sulphur-sprayed fruits. Trials with New Spray Materials Tests of promising new fungicides for the control of ripe spot have been carried out by the Plant Diseases Division over the last 3 years, the earlier trials being laid down by Taylor, formerly an officer of the Division. Materials tested were as follows: 1. Bordeaux mixture, applied at 2:6: 100 in mid-January and 1:2: 100 in mid-February. To each spray was added Boz. of casein-lime spreader,

Lesions of ripe spot on Sturmer apple; natural infection. After Taylor and Brien. consisting of a mixture of equal weights of casein powder and hydrated lime. 2. Fixtan (3.75 per cent, phenyl mercury compound). 3. Zerlate, containing 70 per cent, ziram (zinc dimethyl dithiocarbamate). 4. Zirospray (70 per cent, micronised ziram). 5. Fermate, containing -70 per cent, ferbam (ferric dimethyl dithiocarbamate) . The new fungicides, all wettable powders, were tested at two concentrations and there were two applications at each concentration. The timing of applications was similar to that of Bordeaux sprays. Other treatments consisted of checks not receiving any fungicidal spray and a general spray schedule consisting of usual spray treatments, including lime sulphur, colloidal sulphur, lead

arsenate, and hydrated lime. Either of these treatments was used in assessing the relative efficiency of other materials tested. Experimental layout comprised five Experimental layout comprised five replications of each treatment randemised in blocks, each replication consisting of three ' trees. . Ripe spot and spray injury were recorded from one sample case per tree at harvest, the sample consisting of the top layer of all cases picked from the tree. Fruit was sorted into that free from ripe spot and that having one or more lesions. A similar sample was also cool stored and records were taken the following spring. Considerable difficulty was experienced in dislanguishing between light ripe spot infection and spray injury on fruit sprayed with Bordeaux mixture. Results were submitted to statistical analysis. Data are given in actual and transformed figures in the table on the previous page. Under the conditions of the tests the table shows that all treatments aS compared with checks or general spray schedule gave significant reduction of ripe spot infection. Differences between treatments other than checks and general spray schedule were as follows: —

Trial 1: Bordeaux mixture gave significantly lower incidence of ripe spot at harvest than either Fixtan or Fermate. Zerlate also gave better control than Fermate. After storage, however, differences between the above treatments were no longer above treatments were no longer significant. Trial 2- Differences were not signi- . ficant at harvest> but"XX Bordeaux and Zerlate gave a significant reduction of ripe spot infection as com pared with Fixtan and Fermate. . Trial 3: Zirospray at 31b. in 100 gallons of water gave highly significant results when compared with Zirospray at 1.51 b. or Bordeaux mixture. Bordeaux mixture caused the usual type of russet and light to severe blemish (red stipple markings) of fruit, which was very similar to ripe S p O t damage. Bordeaux spray residues were also difficult to remove. In other treatments fruit was much brighter and smoother skinned than that from Bordeaux plots. In Fixtan (21b. in 100 gallons of water) plots occasional fruit showed slight red coloration and russet round the Cal F X - In general, from the experimental evidence presented here materials based on Ziram were equal and in one instance superior to Bordeaux mixture in reducing ripe spot infection.

The following spray treatment is recommended by the Department of Agriculture for control of ripe spot; Mid-January, Bordeaux 2:6:100. Mid-February, Bordeaux 1:4: 100. m ,,,, . ~ , o of caseffi-lime 3 spreader. be added Boz. case j n _ii me spreader, Materials based on + Ziram are also recommended j for trial by frurt mid-Januarv and mid-Februarv The Sncentration of Ziram used should be 141 b, hence materials contesting 70 at the rate of 21b. in 100 gallons of water. Acknowledgment Thanks are expressed to Mr. J. M. Thorp for permission to conduct a • trial on his property and for valuable assistance with spray applications. Literature Cited woodhead, C. E. (1950): "The Orchardist of New Zealand”, vol. XXIII No. 11, pp. 7-9. Taylor, G. G., and Brien, R. M. (1943): "The New Zealand Journal of Science and Technology”, vol. 25, No. 2 (Sec. A), 63-72 n H t f vol xvn No 2 nn 3-5 ° f T . „ ’ << T h n >P 7i h Jo Si o f Science and’ vol 28 No 2 (Sec A) pp 139-144 Tlo G G (1946) . .. The New Zealand journal of Science and Technology”, vol. 27, No. 6 (Sec. A), pp. 457-469.

Pedigree Sow Records

♦ This treatment caused spray injury as outlined in text.

Treatment Mean percentage Infection (or equivalent angle) Tria) 1 Trial 2 (Sturmer) Trial 3 Concentration in (G. Delicious) Mean percentage infection (or equivalent angle) Trial 1 (Sturmer) Trial 2 (Sturmer) Trial 3 (G. Delicious! 100 gals. water Harvested in % infection Har- May vested Stored % In- Equiv. May 1 frith. fection angle 100 gals, water Harvested in % infection HarMay vested Stored % In- Equiv. May 1 mth. fection angle Harvested in Stored May 3 mths. % In- Equiv. % In- Equiv. fection angle fection angle Harvested in Stored May 3 mths. % In- Equiv. % In- Equiv. fection angle fection angle Check ■ 40.3 40.3 46.5 46.5 22.3 22.3 29.7 29.7 85.1 85.1 67.3 67.3 — — — <Lime sulphur 0.5 General I gals., colloidal J sulphur (40%) schedule j 21b., hydrated / lime 31b., lead — — — — 7— — 72.1 58.2 V arsenate 1.51b. — — — — — — 72.1 58.2 ♦Bordeaux 1 • mixture 2:6:100; 1:2:100 16.3 21.1 4.1 11.6 32.8 34.5 43.8 41.6 Fixtan lib. 23.6 21.2 — — — — — — — Fixtan 21b. — —— 6.0 14.2 54.2 47.3 —— . — 6.0 — 14.2 54.2 47.3 • — Zerlate 1.51b. 19.9 23.4 — — — — — — — — • — • Zerlate 3.01b. — — 6.5 14.7 27.1 31.4 — — Zirospray 1.51b. — —— — — — — 38.7 38.4 Zirospray 3.01b. — — — — — — 3.6 10.9 Fermate 2.01b. 28.7 26.9 — — — — — — Fermate 3.01b. — — 4.4 11.9 45.4 42.3 — — Difference required for signi6.7 6.7 4.1 7.8 9.6 ficance a 5 per cent, level 6.7 6.7 4.1 — 7.8 — . 9.6 5 per cent, level

EFFECT OF SPRAY APPLICATIONS IN MID-JANUARY AND MID-FEBRUARY ON CONTROL OF RIPE SPOT

Owner's name and address Ayson, W. R., Otautau Ayson, W. R., Otautau .. •• Hodgkinson, H. E., Westland Hodgkinson, H. E., Westland Hodgkinson, H. E., Westland Pohangina Pig Club, Ashhurst Pohangina Pig Club, Ashhurst Pohangina Pig Club, Ashhurst Smith, F. E., Hauraki Plains Smith, F. E., Hauraki Plains Barnes, A. H., Kaikoura Barnes, A. H., Kaikoura Bay R., Nelson Davies, T. L., Ohaupo Davies, T. L., Ohaupo Davies, T. L., Ohaupo Goymer, T., New Plymouth Harper, R. J., Ohinewai Harper, R. J., Ohinewai Harper, R. J., Ohinewai Harper, R. J., Ohinewai Harper, R. J., Ohinewai Harper, R. J., Ohinewai Harper, R. J., Ohinewai Harper, R. J., Ohinewai Hope, W. D., Rotorua Knight, M. H., Levin Knight, M. H., Levin Knight, M. H., Levin Levin Co-op. Dairy Co. .. Levin Co-op. Dairy Co. Mundy, R. S., Whakatane .. New Plymouth High School Board New Plymouth High School Board New Plymouth High School Board ard ard >ard New Plymouth High School Board Pohangina Pig Club, Ashhurst Pohangina Pig Club, Ashhurst Pohangina Pig Club, Ashhurst Risi, W., Hawera .. .. .. .. Risi, W., Hawera .. .. .. Risi, W., Hawera Risi, W., Hawera

Herd book number Number of pigs Litter weight Grade of litter Sow Sire Born Weaned 3 weeks lb. . 8 weeks lb. Berkshire 22147 22907 8 8 105 316 2 22147 . 9458 11 11 132 378 1 (L.W.) 11 11 132 378 1 23921 25161 14 10 126 417 1 25758 25161 9 8 116 327 2 23921 25161 16 8 124 332 2 24968 25218 7 5 58 173 — 24968 25218 9 8 81 316 4 24968 25218 10 9 91 348 3 Tamwortb I 16377 16781 11 1 9 143 399 1 I 17090 17156 1 9 1 9 96 ■ 296 3 Large White 9670 9672 8 8 95 287 3 9671 9672 9 6 71 226 7989 7884 12 8 83 289 1 7591 8520 11 11 203 522 1 7788 8520 8 8 128 335 2 7591 . . 8520 12 9 179 423 1 7925 7567 12 10 140 482 i 8405 8711 8 8 109 362 2 7305 7836 14 9 132 410 1 8230 8364 15 13 165 502 1 8405 7836 8 6 94 299 3 6343 9125 ' 6 6 72 211 5 7305 9125 14 6 84 268 4 8405 9406 13 11 133 466 1 7305 9125 10 9 116 413 2 8889 7194 8 8 98 293 3 9310 8695 . 9 9 85 289 4 9310 7955 12 11 143 510 1 9310 7955 16 13 152 536 1 9308 9369 14 9 64 189 . — 7872 9369 10 9 99 242 4 7485 8835 14 11 142 417 1 7916 7567 12 9 128 339 2 7909 7567 10 8 168 350 2 8538 7913 10 . 9 145 372 I (Eng.) (Eng.) 7916 9687 12 9 149 384 1 8900 8879 9 7 56 219 — 8900 8879 10 10 91 334 3 8900 8879 11 9 70 209 — 8611 9009 11 9 108 329 2 8612 9009 13 9 138 390 1 8282 9009 8 8 121 305 2 9010 8782 12 11 151 448 1

In the period April 1950 to December 1951 the following breeders had pig litters graded as shown:—