THE CULTURE OF SET ONIONS 9 



FACTORS AFFECTING LOSSES FROM DISEASE 

 IN THE FIELD AND IN STORAGE 



Weather 



Seasonal weather conditions, more than any other single factor, determine the 

 extent to which decay develops in the Connecticut Valley set onion crop. In 

 general, high losses from decay follow wet seasons and low losses follow dry ones. 

 The 1937 and 1938 growing seasons were abnormally wet, and losses from decay 

 were high in most crops. The growing seasons of the two following years were 

 abnormally dry, with the result that few instances of excessive loss from decay 

 were reported. 



The weather occurring the latter part of the growing season, more particularly 

 during the time of harvesting operations, is most important. It is during this 

 period that the average onion bulb is most susceptible to infection by disease 

 organisms. Young, rapidly growing bulbs or mature bulbs that have been 

 harvested and well cured are apparently much less likeh' to become infected. If 

 the weather is wet during this critical period, the maturity of the crop may be 

 delayed and harvesting and curing greatly prolonged. Many bulbs become in- 

 fected by disease organisms so that subsequent losses from decay are high. If 

 the weather is dry, the crop matures quickly and the harvested bulbs dry and 

 cure rapidly. Few bulbs become infected and losses from decay are light. 



While seasonal weather conditions have an important bearing on the yield and 

 quality of the onion crop, nothing can be done directly to control them. How- 

 ever, there are other important factors affecting yields and quality of onions, 

 which, if properly controlled, will offset to some extent the effects of unfavorable 

 weather. 



The Quality of Seed Sets 



Locally Grown Versus Imported Sets. — The opinion is prevalent among local 

 growers that onions grown from sets raised in the Connecticut Valley keep better 

 in storage than onions grown from sets raised in other set-producing sections. 

 To determine whether or not this is so, onion sets from different sources were 

 grown in 1939 and again in 1940. The results for both years support the growers 

 in their belief that locally produced sets give, on the average, a better keeping 

 crop of onions. The following table summarizes some of the results obtained in 

 1939. 



Table 6. — The Performance of Five Lots of Locally Grown Jap Sets 

 Compared With Five Lots of Imported Jap Sets. 



