U. S. DEPARTMENT OF AGRICULTURE, 
 
 l;i UK.W OF PLANT [NDUSTRY— Circular No. 39. 
 
 B I GALLOWAY, Chief of Bureau. 
 
 THE DECAY OF CABBAGE IN STORAGE: 
 
 ITS CAUSE AM) PREVENTION. 
 
 L. L. IIAKTEK, 
 A.8SISTAN1 Pathologist, Cotton and Truck Disease 
 
 I WVESTIGATIONS. 
 
 •• • Cll 39 09 
 
 WASHINGTON : GOVERNMENT PRINTING OFFICE : 1809 
 
 
 UNIV OF Fl l_i£ 
 DOCUMENTS DEPT. 
 
 
 
 *% *S S*\ 
 
 
 
 -POSITORY 
 
 
BUREAU OF PLANT INDUSTRY. 
 
 Chief of Bureau, Beverly T. Galloway. 
 Assistant Chief of Bureau, Albert F. Woods. 
 Editor, J. E. Rockwell. 
 
 Chief Clerk. James E. Jones. 
 
 [Cir. 39] 
 2 
 
ii. r 1 
 
 THE DECAY OF CABBAGE I\ STORAGE: ITS CAUSE 
 AND PREVENTION. 
 
 INTRODUCTION. 
 
 The loss from deca) of cabbage in winter storage has men. 
 to such an extent in some districts in the pasl few years as freqneniSy 
 to make the growing of this crop an almosl unprofitable industry. 
 Of ilif thousands of tons stored every fall to supply the markets in 
 the winter, from LO to 50 per cent is losi annually from decay. Soon 
 after the cabbage is put in the storage house many of the outer leaves 
 of the heads turn black and become soft. In order to meet the 
 requirements of the market it i- necessary to pull off several of the 
 outer leaves, thus reducing materially the size of the head. 
 
 Investigations into the causes of the decay of cabbage in storage 
 and into the mean- of preventing ii were undertaken for the purpose 
 of determining the factors contributing to this loss and what prac- 
 ticable remedial measures can besl he employed to reduce it to a 
 minimum. 
 
 It was accessary \<< determine the extent to which bacterial organ- 
 isms and leaf-blighl were responsible for the trouble and how tiny 
 gained access to the tissue of the cabbage. This investigation 
 necessitated a stud) of the disease affecting cabbage in the fields 
 from which storage -lock was obtained and of the methods of han- 
 dling the crop when being harvested and placed in storage houses. 
 
 A the development of the bacteria and the leaf-blighl which are 
 larger) responsible for the decay of cabbage depends on temperature 
 and humidity, a study was made of the construction of the houses, 
 with a \ ieu to the control of these factors during the storage period. 
 
 These studies must be regarded as preliminary, undertaken to 
 learn the nature and importance of the problem. The writer has 
 observed in the fields the method of harvesting and storing cabbage 
 during two seasons. Examinations were also made of house- where 
 loss occurred and of those relatively free from loss. During a period 
 of several mouth- the range of temperature and the relative humidity 
 in such houses were observed. 
 
 is paper was prepared al the request ( Corbett, Borticulturisl .if 
 
 i Planl Industry . after a study of conditions in the State of .New York. 
 Ii has reference especially to the northern cabbage districts, from New York to Minne- 
 sota, where the winter storage of this crop is largely practiced. It aim- men 
 diagnose the situation ami outline plainly Deeded preventives I'. T Gai 
 
 [Cir. 39 J ;< 
 
4 THE DECAY OF CABBAGE IN STORAGE. 
 
 The conclusion has been reached that cabbage which comes to 
 storage in good condition can be preserved if the best types of stor- 
 age houses are adopted and the temperature and humidity properly 
 regulated by careful ventilation, but this is only one phase of 
 the storage problem. Its complete solution is not likely to be 
 reached until the problem is taken up from the field standpoint and 
 demonstrations made of the influence on keeping quality of methods 
 of culture, care in handling, time elapsing between harvesting and 
 storage, etc. The Bureau of Plant Industry has already shown the 
 important influence of these factors on the keeping of oranges and 
 other fruits. 
 
 That, a great improvement can be made in the technique of cab- 
 bage storage is not to be doubted, but until the time arrives when 
 funds for such work are available the suggestions in this circular 
 may assist cabbage growers and warehousemen to reduce their 
 losses. 
 
 FACTORS CONTRIBUTING TO DECAY. 
 
 It seems hardly necessary to emphasize the point that no diseased 
 cabbage should go into winter storage. Diseased heads not only do 
 not keep well, but they become the source of infection for healthy 
 stock. 
 
 FIELD INFECTIONS. 
 
 All three of the diseases causing loss of cabbage in storage may 
 originate in the field. Black-rot, so far as known, always results 
 from infections in the field. An examination should be made of all 
 cabbages before storing, and heads affected with black-rot rejected. 
 Frequently only very slight traces are observable, and it is perhaps 
 permissible to store such heads for short periods. Their keeping, 
 quality has, however, become impaired and they should be marketed 
 early. Cabbage that has been frozen in the field should either be 
 allowed to thaw and dry before going into the storage 1 house or be 
 rejected altogether, as frozen cabbage does not keep well. 
 
 The soft-rots are less common in the field, lint when they occur 
 are often very destructive. Special care should be taken to reject 
 cabbages which show traces of soft-rot when brought in for storage. 
 
 Leaf-blight is quite common in some fields, but is usually confined 
 to flu 1 outer leaves, which can he removed before storing. This 
 disease is usually regarded as less important than the soft-rots, as 
 its further development <an be prevented by proper ventilation of 
 the storage 1 house. 
 
 HOUSE INFECTION. 
 
 If a house has been used for one or more seasons for storage pur- 
 poses and there has been am evidence of decay, it is a good plan to 
 disinfect the interior of the building in the fall before new slock is 
 put in. The spores of many fungi and bacteria can retain their 
 
 [CIr. 39] 
 
THE DECAl 0] C \iu; \i,l. I ,\ STORAGE. 5 
 
 vitality for a long time. If the) are lefl in a house thai lias qoj 
 been disinfected From one season to the next, the newly stored crop is 
 exposed to infection whenever temperature conditions are favorable. 
 Spraying the walls, ceiling, and benches with about a half of I per 
 cent solution of copper sulphate 1 or the application of a whitewash 
 alone, either of which could be applied with the usual spray pump, 
 would he cheap and practicable. An application of either a copper 
 solution or whitewash should he made long enough before the house 
 is used for storage to permit the wood to dry thoroughly. 
 
 CARELESS II \ \ M INC. 
 
 A large proportion of the decaj in stored cabbage doubtless origi- 
 nates in bruises due to rough handling. Plant tissues are well pro- 
 tected against decay so long as they are uninjured, but any break in 
 tin 1 epidermis may serve as a starting point of decay. 
 
 Whole loads of cabbage have been seen at the storage house with 
 scarcely a head not bruised and torn from careless handling. Cab- 
 hould he given the same attention that expert fruit packers 
 give to apples. The heads should never he Thrown into the wagon 
 when gathering in t he field or t hrown from i he wagon to the bin when 
 unloading, hut always passed from hand to hand. 
 
 ORGANISMS CONCERNED IN DECAY. 
 
 An examination of cabbage undergoing decaj in storage shows 
 t hat t hree kinds of organisms black-rot , soft-rot , and leaf-blighl are 
 principally concerned in producing the injury. 
 
 BLA< K R< •! . 
 
 Black-rot is one of the most serious diseases of cabbage in the held 
 and is responsible for much of the loss from decay in storage. It is 
 caused by a parasitic bacterium" which gains access to the young, 
 growing plants through the roots or through marginal infection of 
 the leaf. The bacteria then grow up from the loots or down from 
 the point of infection of the leaf, through the fihro-vascular bundles, 
 tot he head. The black-rot organism itself, under storage condil ions, 
 seldom completes i he destruction of the head, hut cabbages affected 
 by it are more liable to attack by soft-rot bacteria and by fungi, 
 which .level.. p rapidly under favorable conditions. The control of 
 black-rot in the field, therefore, will greatly reduce the loss from 
 decay in storage. 
 
 Upon cutting across the stem or through the leaf black-rot can be 
 
 detected by the black ring in the woody part of the stem and by the 
 
 blackening of the veins of the leaves. 
 
 /• campest ■ Pam Erw. Sra. 
 
6 THE DECAY OF CABBAGE IK STORAGE. 
 
 SOFT-ROT. 
 
 Soft-rot is clue to a group of related species of bacteria rather than 
 to one species. The bacteria gain access to the tissue of the leaves 
 of the cabbage principally through wounds made by careless handling 
 and by infection of the stem and leaves previously attacked by 
 black-rot. Other crops, such as carrots and turnips, are subject to 
 similar injury. The soft-rot bacteria as a class are marked by their 
 ability to destroy plants very quickly under favorable temperature 
 conditions. They seldom affect uninjured plants, but require a 
 wound or other injury in order to gain a foothold. 
 
 LEAF-BLIGHT. 
 
 Leaf-blight is due to a fungus" which attacks the plant at any stage 
 of its growth but is more likely to develop on a plant subjected to 
 unfavorable conditions. In the seed bed and in the field, leaf-blight 
 is distinguished by the dark, mildewed spots it produces on the 
 leaves. In warm storage houses and in the presence of sufficienl 
 moisture it spreads very rapidly over the leaves and causes consid- 
 erable loss from decay. The fungus can not grow, however, at a 
 temperature near freezing and in the absence of humidity. 
 
 STORAGE CONDITIONS NECESSARY FOR PREVENTING DECAY. 
 
 The most favorable results in the preservation of cabbage are 
 secured only by the skillful regulation of the temperature and humidity 
 through daily attention to the ventilation of the houses. Tempera- 
 ture and humidity are the most important factors to be considered in 
 connection with cold storage. If the proper temperature', along with 
 thy houses, could he kept, the organisms which cause the decay of 
 cabbage would be held in check. In other words, the organisms would 
 not develop if the temperature could be held at about one degree 
 above the freezing point. Since it is impossible, owing to periods of 
 warm weather in the winter, to maintain such a uniform tempera- 
 ture, humidity plays an important part. Decay would he much less 
 in a house with high temperature and little humidity than in a 
 house with high temperature and a relatively large amount of 
 humidity. 
 
 Temperature and humidity must largely he controlled by a well- 
 planned system of ventilation with outdoor air. When a, long 
 period of very cold weather makes it impossible to keep the tempera- 
 lure at a little above freezing, one or two stoves can he put in the 
 house, which would also materially reduce the humidity. Moisture 
 should not he allowed to condense on the cabbage, and not very 
 
 " Alternaria bri Berf : ice. 
 
 [Cir. :i'.i] 
 
I III DECAY OF CABBAGE IN STORAGE. 7 
 
 much on the walls and ceiling. Whenever moisture is condensed on 
 the cabbage the house is in bad condition and should be dried al once, 
 even if a stove must be put in and the temperature raised. After 
 drying, the temperature could be reduced by admitting outside air 
 through the doors. When stoves arc put in houses 'arc should be 
 exercised thai too much smoke docs not escape inside, as this 
 would probably injure the sale of the cabbage. 
 
 It is only in extreme eases that the proper condition of the house 
 can not be maintained by ventilation with outside air. Cabbage is 
 constantly giving off moisture unless frozen, [f a house is kepi closed, 
 the relative humidity will increase until the air is saturated. Any 
 reduction in temperature would then condense the moisture on the 
 cabbage and the walls of the house. It is believed that the house 
 should be opened every day except when warm or very damp. The 
 house should be opened for ventilation during clear weather when 
 the air is dry, and at a time of day when the temperature is near the 
 freezing point. The temperature of the house would then he little 
 changed, and the relative humidity inside would he reduced to that 
 of t he air outside. 
 
 In a storage house of a capacity of about 1,600 tons, in the State 
 of New York, a system of ventilation has been installed which con- 
 sists of pipes ru nning through the building, through which the air in 
 the house i> drawn by a fan run by electric power. The pipes grad- 
 ually decrease in size as they ramify through the building. It is 
 claimed that h\ such a system the air can he changed in the whole 
 building in twenty minutes. The owner makes h a practice to change 
 the ail- once every twenty-four hours unless the temperature isvery 
 high and the air humid. His stock, when seen in midwinter, was in 
 excellent condition. No decayed heads nor any moisture condensed 
 on t lie cabbage were found. 
 
 CONSTRUCTION OF STORAGE HOUSES TO PREVENT DECAY. 
 
 Since the objeel in storing cabbage is to keep the house near the 
 freezing point and as dry a- possible, the construction of the house is 
 important only in so far as it contributes to that end. It is probable 
 that the best t\ pe of house is made of hrick or stone, the walls being 
 Is to ■_' l inches in thickness. Thick walls are essential, since, being 
 less affected h\ varying temperature-, they make it possible to keep 
 the interior cool during a period of warm weather. The roof should 
 he made of the usual sheathing and shingles. It would he preferable 
 to have the sheathing run from the comh of the roof to the eav< 
 which would enable the water, if frost forms and melts on the inside, 
 to run to the side of the building instead of dripping on the cabbage. 
 
 |( ir. 39] 
 
8 THE DECAY OF CABBAGE IX STOKAGE. 
 
 A house 100 feet in length should have at least four ventilators on 
 the comb, which would permit outside air coming in from below to 
 drive the warm, damp air out through the top. A building made of 
 wood, with the walls two or three boards thick, though not as good 
 as a stone house, has in many cases given good results. 
 
 METHODS OF STORING CABBAGE. 
 
 There are two common methods of storing cabbage — in bins and 
 on shelves. Both have their advantages. Most storage men prefer 
 to use bins, because in this way a larger tonnage of cabbage can be 
 stored per cubic yard of space. Others, however, store on shelves, 
 believing that the cabbage keeps better. 
 
 The aeration in bins is at best not good, and for that reason shelves, 
 where the heads are only two or three deep, are preferable. When 
 stored, the cabbage should be placed with the stem end upward, so 
 that all water dripping from the ceiling or any moisture that may 
 condense on the leaves will more readily run off. 
 
 CONCLUSIONS. 
 
 Soft-rot and leaf-blight are the immediate causes of the decay of 
 cabbage in storage. The organisms causing these decays gain access 
 to the tissues of the leaves through wounds made by careless handling 
 and also by following up the fibro-vascular bundles which have been 
 previously killed by black-rot. 
 
 Diseased or badly bruised cabbage should not be stored. The 
 most important factors in the keeping of cabbage in storage are tem- 
 perature and humidity. Water should not be allowed to accumu- 
 late in drops on the cabbage, and if it does immediate steps should 
 be taken to dry the cabbage, either by admitting air from the outside 
 or by the use of stoves inside. Stoves should not be used, however, 
 if it is possible to obtain (he same results by using cold, dry, outside 
 air. Houses should be opened and ventilated every day except 
 when the air is dam]) and warm. Cold weather, when the tempera- 
 ture is at about the freezing point, is best for ventilation. 
 
 The construction of houses, the methods of storing, etc., are impor- 
 tant in so far as they contribute to the keeping of dry houses and the 
 maintenance of a uniform temperature slightly above freezing. 
 
 Approved: 
 
 James Wilson, 
 
 Secretary of Agriculturt . 
 
 Washington, 1). C September 9, 1909. 
 
 [Cir. 39.] 
 
 
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