MARKET DISEASES OF FRUITS AND VEGETABLES 7 



Whether it is due to high temperature, sunscald, or some physio- 

 logical disturbance is not known. 



The early symptoms of waxy break-down are small, slightly sunken, 

 light-yellow areas in the flesh of the clove. As the break-down pro- 

 gresses the clove shows a deep-yellow or amber color throughout 

 (pi. 2, B). The clove is then somewhat translucent and sticky or 

 waxy to the touch but not soft, as in the case of tissues broken down 

 by parasitic organisms. The outer dry protective scales are not af- 

 fected. No indications of break-down may show externally until 

 the advanced stage is reached, when the shrinking of the clove and 

 the amber-brown color may become noticeable through the white 

 papery outer scales. 



ASPERGILLUS BULB ROT OF ONIONS 



{Aspergillus alliaceus Thorn and Church) 



Although aspergillus bulb rot has not yet been found in the United 

 States, the causal fungus has been intercepted at ports of entry in 

 garlic from Italy. As inoculation tests have proved that this fungus 

 is pathogenic to American onions and garlic, it may become of 

 economic importance in this country. 



On inoculation of garlic and mature onions the first sign of disease 

 is a slight swelling and a darkening of the tissue. This affected area 

 becomes water-soaked and soft, and a sharp line of demarcation occurs 

 between the diseased and the healthy tissue. In advanced stages the 

 tissue shrinks and becomes brownish and a white mat of mycelium 

 forms between the bulb scales. Eventually, small white sclerotia 

 form, which later become dark brown at maturity. The spore clusters 

 appear yellowish brown and are produced in great abundance on the 

 surface of the decaying tissue if the humidity is high. 



Infected bulbs are completely decayed within 21 days when held 

 at 96 8° F. Practically no decay develops in inoculated bulbs kept 

 for 3 months at 60.8°. The results of attempted inoculations of 

 growing plants indicate that the fungus is not able to attack them 

 and that it may become important only as a decay-producing organism 

 of the matured bulbs. 



No control measures have been developed. 



(See 51) 



BACTERIAL SOFT ROT OF ONIONS 



(Erwinia carotovora (Jones) Holland) 



Bacterial soft rot occurs in all onion-growing districts in the United 

 States but is most common in onions harvested during warm, rainy 

 seasons or in those that develop sunscald during the curing process. 

 It is often serious in imported Spanish onions, especially after the 

 sprouting tops are cut off. 



This decay occurs in the field, where it causes some losses, and in 

 transit and storage, where the losses frequently are very heavy. The 

 affected tissues are glassy or water-soaked at first, later becoming soft 

 and mushy (pi. 3, A). The rot usually is accompanied by a very re- 

 pulsive odor. The bacteria that cause it apparently cannot pene- 

 trate the dry unbroken skin of the onion. In the field they generally 



