34 BULLETIN 395, U. S. DEPAETMENT OF AGEICULTUKE. 



throughout the development of the lesions. Sporulation upon the 

 fruit, therefore, may be very abundant, but its duration is relatively 

 brief, especially in the case of early varieties. 



Supporting records. — In Georgia in 1912 and 1913, conidia were usually found in 

 greater or less abundance upon fruit lesions as soon as the infections became macro- 

 scopic, and under favorable conditions spore production occurred abundantly through- 

 out the earlier stages of development of the spots. With the advent of the heat and 

 drought of midsummer and late summer, however, sporulation upon the older lesions, 

 especially those in which the diseased areas had been cut off from the surrounding 

 normal tissues by cork layers, became practically or entirely nil. 



ON TWIGS. 



« 



Conidia may be produced upon twig lesions, under favorable con- 

 ditions, as soon as infection becomes visible. Usually they are borne 

 only sparsely dming the season in which the infection occurs. In 

 the following spring, under favorable conditions, spores ordinarily 

 appear in abundance upon overwintered twig lesions soon after the 

 blossoming period of the peach. Subsequently, during moist periods 

 throughout the spring and early summer they are borne profusely 

 from this source. Usually, however, under the conditions of north- 

 em Georgia, sporulation from these lesions diminishes rapidly in mid- 

 summer and becomes practically nil in late summer. Spores may 

 thus be produced in considerable abundance upon twig lesions at any 

 time during the growing period of the host. 



Supporting records. — Under field conditions, diu-ing their first season's development, 

 twig lesions uniformly produced conidia very sparingly. In some cases spores were 

 sparsely e\'ident microscopically in the earliest macroscopic stages of infection; in 

 others, the lesions produced only occasional conidiophores and conidia in the coiuse 

 of the summer. In practically all such cases observed, the conidiophores were pro- 

 duced singly, and only rarely were they abundant in the field. In moist chambers, 

 howeA^er, spores were borne abundantly upon such lesions, though the conidio- 

 phores were not borne in tufts. 



With the advent of spring, conidiophores appeared in abundant macroscopic olive- 

 green tufts upon overwintered lesions. In 1913 these were first observed on April 1, 

 when the trees were in full bloom. Careful microscopic examinations, however, 

 revealed no conidia. Occasional conidia were foimd upon such hyphae on April 11, 

 while on April 15 and 18 they were observed in slightly increased numbers. On 

 account of phenomenally dry weather, spore production was very sparse tlxroughout 

 the spring; but the fact that it would have been more abundant under favorable con- 

 ditions was demonstrated by the abundant sporulation which occmTed when twig 

 lesions were held over night in a moist chamber. After the rains of early summer, 

 spores were observed in abundance. In midsummer and late summer, however, they 

 became more and more sparse on the overwintered lesions and more numerous on the 

 cm-rent year's infections. As late as August 21 conidia were observed in fair abun- 

 dance upon lesions on the old wood. 



ON LEAVES. 



Conidia may occur upon the leaves as soon as the infection is evi- 

 dent, and sporulation may continue under favorable conditions 

 throughout the development of the lesions. Inasmuch as most 



