100 



JOURNAL OF AGRICULTURE OF P. R. 



Fig. 1 8. — Portion of fruit 

 rotted by TUplocUo in damp 

 chamber. Note the floccu- 

 lent mycelial masses, each 

 of which encloses a pycni- 

 diiim or sj^ore-producing 

 sac. 



at the blossom end by the time the softened area at the opposite 

 end is an inch or two in diameter. Externally at this sta^c it aji- 

 pears as if infection had occurred at both poles of the fruit. The 

 two areas rapidly coalesce. If attached to the tree at the time of 

 infection, the fruit remains hanging but a short time only. Two 

 or three days is ordinarily sufficient for the complete rotting of a 



fruit. Rotted areas at first show only a 

 vc'!'y slight cliange in color, but so<m be- 

 come light brown or tan, sometimes with 

 lilack bands corresponding to the sections 

 of the fruit. Tlu^re may or may not be 

 present an amber-colored juice exudate. 

 After falling the fruit is rapidly con- 

 sumed, shrinking, and ultimately liecom- 

 ing black and mununified. At this latter 

 stage it will be covered with numerous 

 minute, pimple-like projections, each of 

 which represents a fruiting body of the 

 causative fungus, DipJodia nainlcnsia. 

 The .s])ores or conidia are produced in 

 these pycnidia in enormous numbers. 

 There is seldom any loss from this source of rot until the fruit is 

 full growm, but from that period on, there is an increasing tendency 

 to decay, particularly during periods of very wet weather. 



In addition to this typical stem-end form, attack may tak(^ pUice 

 at any point on the surface, particularly through insect punctures, 

 bruises, or other injuries. Where one of a cluster of fruit is infected, 

 the fungus, by w^orking back into the fruiting twigs, attacks suc- 

 cessively the others, killing back the branch as well for some dis- 

 tance. This is especially liable to occur where props are used, such 

 a procedure apparently weakening the resistance of fruit and bi-anch 

 by cutting off the sap flow. 



Rotting may occui- at any time during the operations of picking, 

 packing, and shipping, and i;nder present conditions is very preva- 

 lent during the latter stage. Lack of refrigeration and the conse- 

 quent high tem})erature and humidity make ideal conditions for 

 excessive rot on shipboard. 



Several types of soft rot are distinguished by those who handle 

 the fruit in New York, principally based on the portion of the fruit 

 first attacked and the presence or absence of the juice exudate, but all 

 are due to the one fungus. 



