6 MISC. PUBLICATION -4 4 0, U. S. DEPARTMENT OF AGRICULTURE 



yield or the quality, or both ; others are important primarily in storage 

 and transit ; and some are factors both in the field and on the market. 



Among the serious field diseases are downy mildew {Peronospora 

 destructor (Berk.) Caspary), fusarium bulb rot, pink root, purple 

 blotch, smut, and yellow dwarf (virus) . Less important are root knot 

 (Heteroderamarioni (Cornu) Goodey), rust (Puccinia asparagi DC), 

 and white rot. 



Several serious diseases belong in the group that are primarily im- 

 portant from the marketing point of view. These are bacterial soft 

 rot, black mold rot, blue mold rot, gray mold rot. and smudge. 



Greening (sunburn) and sunscald occur in the field, sometimes caus- 

 ing serious damage at harvesting time and later during the marketing 

 process. 



Chemical injuries (ammonia injury and "alkali spots'') are primarily 

 transit and storage troubles. 



(See 6, 10, 16, 17, 22, 23, 27, 50, 52, 57.) 



Garlic {Allium sativum- L.) is subject to many of the diseases that 

 affect the onion. Aspergillus rot (p. 7), fusarium rot (p. 11 and 

 pi. 2, C), gray mold rot (p. 12), sclerotium rot (see sclerotium rot of 

 beans, p. 30) and white rot (p. 17) are among the most important dis- 

 eases of the bulbs. However, the diseases most often encountered on 

 the market are blue mold rot and waxy break-down. 



BLUE MOLD ROT OF GARLIC 



(Penicillium spp.) 



Blue mold is not often of serious consequence on vegetable crops, 

 but occasionally it causes appreciable decay of garlic and onion bulbs. 

 Stock that shows excessive mechanical injury, freezing, or sunscald is 

 especially subject to blue mold rot during storage or transit if there 

 is insufficient ventilation. 



The early symptoms of blue mold rot are light-yellowish lesions in 

 the fleshy scales of the bulbs. As the decay progresses a fine white 

 surface mold becomes visible (pi. 2, ^L), but this soon changes to 

 blue or bluish green as spores are produced in great abundance on 

 the tips of the fungus filaments. The appearance of this characteristic 

 blue mold serves to identify readily the disease. 



Garlic bulbs affected with blue mold rot may show little or no evi- 

 dence of the disease externally. However, affected bulbs will be light 

 in weight, and pressing on individual cloves will reveal a soft, spongy 

 or powdery-dry condition, depending upon the extent of the decay. 

 In advanced stages of decay the cloves are completely broken down into 

 a dry greenish-tan or gray powdery mass. 



No data are available regarding the rate of development of blue 

 mold rot in garlic during the curing process or while in storage. 



WAXY BREAK-DOWN OF GARLIC 



A yellow waxy break-down of the outside cloves of garlic bulbs 

 is one of the serious troubles that affects the marketability of this 

 crop. Little is known as to the cause of this break-down except that 

 no organism seems to be associated with it as a causal agent. 



