654 INSECTS AFFECTING VEGETATION 



fer from some of the ordinary molds which find access to the fruit 

 entirely through bruised or other injured areas. 



The brief storage of quinces usually does not lead to much 

 further development of the quince rot. The fungus in question is 

 commonly the same as that in the apple rot (Sphaetropsis malorum). 



Storage Rots of Potatoes, Onions, Etc. With vegetables we have 

 a very wide range of storage troubles. In the case of potatoes we 

 have two general types of rots, namely : wet-rot and dry-rot. The 

 wet-rot of potatoes commonly result from two causes, viz. : The late 

 blight or rot fungus (Phytophthora infestans D'By.) may be ex- 

 pected to cause considerable losses of the tubers in storage when these 

 have been gathered from Phytophthora infested fields and bacteria 

 may cause rot in injured tubers. In Ohio, as stated under this dis- 

 ease of potatoes, the late blight and rot fungus is not commonly 

 prevalent. Perhaps little can be done to preserve the tubers from 

 such fields except to market the crop promptly and to store with 

 especial respect to the optimum conditions. The best temperatures 

 for such potatoes will be warmer than for apples, and it is very de- 

 sirable that moisture be kept as low as possible. 



A wet-rot of potatoes, purely or very largely bacterial in cause, 

 must also be dealt with. This rot bacterium is different from the 

 bacterium of potato wilt (Bacillus solanacearum) and without the 

 latter may also induce considerable decay. It is believed the bacteria 

 producing this wet-rot gain entrance through injuries to the tubers 

 and that low humidity dry storage is especially desirable in keep- 

 ing down losses from this source. (Ohio E. S. B. 214.) 



Dry-rot of potatoes is due to a fungus (Fusarium oxysporum) 

 which appears to belong among our soil infesting fungi. This fun- 

 gus appears to be the cause of premature dying of the potato plants 

 and it certainly survives in the tubers from such infected plants. 

 At harvest time, as shown under dry-rot of potato, tubers show in- 

 fection at the stem end. Subsequently during storage the fungus 

 penetrates more deeply into the tubers and will often produce dry- 

 rot of the infected tubers. Further descriptive matter concerning 

 dry rot will be found in the special part of the bulletin under potato. 

 For storage of such infected tubers, as well as for the general crop, 

 it is desirable that storage temperatures be kept about 42 degrees 

 Fahr., or slightly lower. 



Sweet potatoes also suffer from >a large variety of rot troubles. 

 These sweet potato rots are more or less special in character and 

 since the crop is not largely handled in cold storage, nothing is 

 here offered in addition to what appears in the special part of the 

 bulletin. 



Onion Rots in Storage. Onion rots are a serious matter with 

 onion growers and onion dealers as well. It has been found that par- 

 ticular varieties of onions in our climate are susceptible to special 

 diseases. For this reason we must consider white onions such as 

 White Silverskin, White King, etc., in a separate class from the rots 

 of red and yellow onions such as the Globe and Wethersfield varieties. 



