14 



MASS. EXPERIMENT STATION BULLETIN 424 



as long as two months did not differ in quality or amount of rot from onions 

 removed to storage immediately after clipping. 



When wet weather prevails at harvest time, the present methods of handling 

 onions during harvesting and curing are conducive to excessive shrinkage and 

 reduced quality. Even perfectly sound bulbs, when left in the field for several 

 weeks, may become so stained that their marketability is adversely affected. 



The 1941 season, while moderately dry, was wetter than 1940. Experiments 

 carried on in 1941 effectively demonstrate the importance of removing bulbs 

 from contact with the ground and giving them protection as soon as possible 

 after pulling. Table 9 shows this clearly. 



Table 9. — Effect of Harvesting Methods on Keeping Quality — Weather- 

 ing IN THE Field Compared With Immediate Protection After Pulling. 



Method of Harvest 



Locally Grown Sets Imported Sets 



Percentage Loss 

 by Nov. 5 



Percentage Loss 

 by Nov. 5 



Onions harvested, stored in 

 bags immediately..- -- 



Onions harvested, bags exposed 

 6 weeks in field before storage. 



9.5 

 15.0 



20.5 

 27.2 



In this e.xperiment the bulbs which were given protection were put into 50- 

 pound onion bags and loosely stacked in a well-ventilated storage building. This 

 method is not practical for general use, since such storage facilities are not 

 available to the average grower. However, another experiment, also carried out 

 in 1941, showed that placing the onions in slatted crates stacked in well-ventilated 

 protected tiers in the field was just as effective in keeping losses to a minimum as 

 placing them in bags in storage. 



Storage Conditions 



Although no experimental work was carried on to show the direct effect of 

 different storage conditions on the keeping quality of onions, frequent visits were 

 made to different commercial storages in the Valley to observe conditions as 

 they existed. In general, the conclusions drawn from these observations agree 

 quite closely with much experimental work that has been carried on elsewhere. 

 Low humidity and cool temperatures retard the growth of sprouts and check the 

 rate of development and spread of rots, while high humidity and high tempera- 

 tures have the reverse effect. 



Cool, dry storage conditions are indispensable for the satisfactory storing of 

 onions but will not prevent onions from rotting. To reduce the amount of rot 

 in storage it is necessary to reduce the number of infections which take place in 

 the field. Once a bulb becomes diseased little can be done to stop the develop- 

 ment of the infection, although the growth of the invading organism is retarded 

 by low humidity and cool temperatures in storage. M. T. Munn (2) states that 

 "but very little secondary infection is believed to take place in storage, since the 

 'contacts' (those healthy bulbs lying against diseased bulbs) very seldom become 

 diseased unless the storage house is very damp and the dry outer skins become 

 soft and full of water. The dry outer scales are usually the last to rot and the 

 disease does not seem to spread from onion to onion thru the dry skins." 



