26 DISEASES OF BEES 



As we see, this disease played almost no role formerly and 

 furthennore it was observed that it sometimes disappeared again 

 spontaneously. We therefore did not bother ourselves much about 

 it. We also became acquainted at this time with the opinion held 

 in the United States, where on the basis of a very wide experience, 

 European foul brood was represented as a deficiency disease, as 

 a disease which only appeared where there were bad beekeeping 

 methods and where the colonies, especially in spring, suffered from 

 hunger, or for some other reason could not develop well. This 

 hypothesis of a deficiency disease was also strongly supported by 

 the very remarkable seasonal occurrence of European foul brood. 

 I find this seasonal occurrence so interesting and so important 

 for an understanding of European foul brood that I should like 

 to discuss it briefly with the aid of Figure 2. You find here again 

 American and European foul brood represented by two lines. 

 The months are indicated above and directly under each month 

 the niraiber of cases of foul brood, in per cent, of the total fxDr the 

 year, observed in this month. f Let us first examine American foul 

 brood. Naturally we have few cases in winter because few inspections 

 are made then. But from spring imtil autumn one can always demon- 

 strate the presence of this disease. We say that we can easily find, 

 American foul brood in a diseased colony at any time. 



It is quite different with European foul brood. It begins slowly 

 in spring, is often scarcely to be demonstrated in the first brood 

 period in April, but increases rapidly, reaching a peak in May and 

 June, then falls back again just as quickly. In autumn, when 

 American foul brood is still very easily demonstrable, European 

 foul brood has practically disappeared without any treatment, but 

 will return again next May and June. We are surprised at the 

 similarity between the seasonal course of European foul brood 

 and that of Nosema infection. Nosema is also most pronotmced 

 in May, and apparently disappears in autumn, only to reappear 

 the following spring. 



We have no certain explanation for this remarkable seasonal 

 occurrence of European foul brood, but it is understandable that 

 one is inclined to find an explanation in the deficiency theory. 

 May and Jime are also highly important months for normal bees. 

 The time of greatest growth, of greatest breeding activity, of the 

 mighty impulse for expansion of the bee colony is found at this 

 time. It is a critical period. In the case of other living creatures 

 and also in the case of man, one speaks of a growth crisis. This 

 growth crisis of the bee colony coincides, imfortunately, all to often 

 with a weather crisis, a setback in the weather in May. Instead of 

 spring warmth and a rich flow of honey, himger and cold invade 



fThis figure shows all the cases of foul brood received at Liebefeld during 

 ihe past 30 years. (About ] ,500 cases of American and 1,200 cases of European 

 foul brood.) 



