46 EXPERIMENT STATION. [Jan. 



Onion Rot. 



BY G. E. STONE. 



In some sections much damasre is occasionally done to onions 

 by the disease known as onion rot. Sometimes one-third or 

 more of the crop is destroyed, occasionally the whole, but in 

 most instances a much smaller percentage would represent the 

 loss. The diseased onions examined by us are generally af- 

 fected with either Botrytis or a species of bacteria and some- 

 times with both. The symptoms caused by both these organisms 

 are characteristic, and easily recognized by careful observers. 

 The rot may be distinguished in the field, but develops further 

 in storage, so that care should be taken to destroy the infected 

 onions before storing, if possible. 



■ Some varieties of onions are said to be more susceptible to 

 the rot than others, and according to our observations unfavor- 

 able seasonal conditions induce the rot. The location of the 

 field is also an important feature, as well as the nature of the 

 soil on which the onions are grown. 



Onion rot appears to be less jirevalent in dry than in moist 

 soil, and we have observed some features which would indicate 

 that it is not so severe on soil to wdiich commercial fertilizers 

 are applied, and which are, in consequence, deficient in organic 

 matter, as on soil fertilized with stable manure, and containing 

 more organic matter. 



Onion rot was severe in some fields in 1907, resulting in 

 considerable loss. The summer of 1907 was very dry, but from 

 the latter part of August on an unusual amount of rain fell, 

 which undoubtedly increased the susceptibility of the crop to 

 this disease. On the other hand, the unusually severe drought 

 of the past summer and fall has no doubt been responsible for 

 the decrease in the amount of the rot. 



