Säilytysaineiden käytöstä porkkanan varastoimisessa

Authors

• Jaakko Mukula Maatalouskoelaitoksen kasvitautiosasto, Tikkurila

DOI: https://doi.org/10.23986/afsci.71287

Abstract

In the years 1948—1950, experiments of carrot storage were conducted with Fusarex, a chemical manufactured by Bauer Products Ltd., at the Department of Plant Pathology of Agricultural Research Institute. Fusarex is prepared for use in potato storage, to prevent rotting and sprouting (3,4). The manufacturer also recommends it for root crops, though the writer of this paper has not found any information in literature about its usefulness for this purpose. Fusarex is a chemical in dust form, and as effective ingredient it contains 3 % of tetrachloronitrobenzene. The recommended dosage is about 0.5 kg. per 100 kg. Preliminary experiments on carrots were also conducted with Belvitan K, manufactured by Farbenfabriken Bayer. Like Fusarex, this chemical is used in dust form and it is prepared for use in potato storage. The recommended dosage of Belvitan K is 0.2 kg. per 100 kg. (1). No information concerning its ingredients is available. The storage sheds used in the experiments were fairly dry and well ventilated. The relative moisture of air varied from 70 to 95 %, temperature from 2 to 6° C. The chemicals were scattered over the carrots as uniformly as possible, in dosages recommended by the manufacturer. The effect of Fusarex was separately tested on sound carrots, on carrots damaged by maggots of Psila rosae Fabr., and on broken carrots. In sheds the carrots were placed in boxes, in some cases mixed with peat or sand. The walls of the boxes were either almost closed or had very large slits in them. The former boxes were used for experimental lots of 20 kg., the latter ones for lots of 4 kg. The storage period was about 6 months. Controls were made twice, after about 3 months’ storage in the middle of winter, and in spring at the end of storage period. At each control the carrots were weighed, and the diseased carrots were removed. In boxes with closed walls rotting of carrots was effectively prevented by Fusarex (cp.the picture 1, p. 86). Only 6—15 % of Fusarex-treated carrots were decayed, while the percentage was 25—71 for untreated carrots. In the preliminary experiment similar results were obtained with Belvitan K. On the other hand, rotting of carrots was only prevented to a slight extent by peat and sand. In boxes with slits in the walls, Fusarex had a favourable effect at the beginning of storage period, if the carrots were not damaged by maggots of Psila rosae. Towards the end of the storage period rotting was not prevented by Fusarex in any experimental group. The results are given in Table 1, p. 88. In experiment 1 in table 1, rotting was chiefly due to Botrytis sp. In experiments 2 and 4plenty of Sclerotinia sclerotiorum (Lib.) De Bary was also found. Each fungus formed plenty of mycelia and sclerotia on the skin of untreated carrots (fig. 1 and 2). If these fungi were found on carrots treated with Fusarex and Belvitan K they grew beneath the skin and rotted the carrots from within. In experiment 3, rotting was caused by Fusarium avenaceum (Fries) Sacc., Botrytis sp., and Stempylium radicinum (M. Dr. & E.) Neerg., the first-mentioned being the commonest of them. Fusarex did not seem to have much effect on Fusarium. As the cause of rotting, the other fungi found in this experiment were of slight importance. Especially towards the end of the storage period, the losz of weight was somewhat greater for untreated than for treated carrots. This was probably chiefly due to easier evaporation of water from diseased carrots as compared to sound ones. Storage with peat at first increased, later prevented the loss of weight. Evidently peat at first absorbed water from the carrots, but later, when it had become wet, it prevented evaporation. Experiments 1 and 2 show that under certain circumstances rotting is effectively prevented by Fusarex. It has an inhibiting effect at least on Botrytis and Sclerotinia, if treatment is conducted before the beginning of the rotting process. Belvitan K seems to have a similar quality. In experiment 3, which was conducted with fairly small experimental lots in open boxes, the effect of Fusarex was of short duration in sound and broken carrots, and in carrots damaged by maggots of Psila rosae it had no effect at all. It is possible that due to open boxes and small storage lots some of the effective ingredient volatilized from Fusarex. This opinion is confirmed by experiments conducted in England on stored potatoes (1, 2). It it also probable that the different result of experiment 3, as compared to experiments 1 and 2, is due to the different types of fungi found in this experiment. On the other hand, it is easy to understand that Fusarex cannot prevent the rotting of carrots damaged by maggots of Psila rosae. The spores of fungi can namely enter the passages dug by the maggots already during the growth period, and the infection occurs before storage. Some firms in Helsinki have experimented with Fusarex in carrot storage. Results have been favourable. The following amounts of carrots were treated with Fusarex in the storage sheds by the following firms: Helsingin kaupungin Elintarvikekeskus 128.000 kg., Kesko Oy 10.000 kg., Oy Tuotevälitys 5.000 kg. In these firms, carrots are usually placed in open bins, in 20—70 cm. thick layers. The temperature in the sheds varies from 2 to 6° C. 1—2 months after the beginning of storage the carrots usually begin to rot so badly that their storage must be interrupted. The progress of the disease can only be prevented to a slight extent by removing the diseased carrots. The firms have reported that losses by disease have been decidedly lower when carrots have been treated with Fusarex. If they were sound when put in storage, the losses caused by fungi were only 0—5 % even after 3—5 months’ storage period. Losses were, however, greater, if part of the carrots were infected, even if slightly, at the beginning of storage. Fusarex-treated carrots were sold to customers in Helsinki. So far they have not been found to be unhealthy or to have a more unpleasant taste than untreated carrots. The taste experiments conducted at Department of Plant Pathology also showed that Fusarex or Belvitan K did not have injurious effects on the taste of carrots.