130 DISEASES OF TROPICAL PLANTS CH. 



and then eventually completely invests the fruits with a dark 

 felt-like rnycelial growth. 



In addition to the diseases given in this chapter, 

 D. M' Alpine in his Fungus Diseases of the Citrus Trees 

 in Australia, and their Treatment, has described the 

 following diseases and the organisms causing them. 

 They are 



False Melanose . . . Cladosporium bruneo-atrum. 

 Black Scurf . . . Coniothecium scabrum. 



Root Rot of Lemon , ) 



Wither Tip jPhoma ommvora. 



Lemon Bark Blotch . . Ascochyta corticola. 



He also gives technical descriptions of a number of 

 other fungi which occur on the citrus fruits, but which 

 are of little economic importance. 



Cottony Mould of Lemons. This storage rot, which is 

 quite common in California, is due to an undetermined 

 species of Sderotinia. The infections occur in the 

 orchards, and the fungus develops in storage, forming a 

 dense, white cottony mass of mycelium, which spreads 

 very rapidly. It penetrates the fruit, producing black 

 sclerotia on the interior. The ascosporic stage is 

 developed from these sclerotia, and these spores can 

 infect either fruit or the cover crop. The fungus is 

 also said to live saprophytically on dead vegetable 

 matter on the ground or parasitically on the twigs of 

 both oranges and lemons. It is believed that the most 

 common source of infection is from the cover crops. 

 Probably the best method of combating this organism 

 will be the washing of the fruit with a good disinfectant. 



PINE APPLE 



Rot. The young plants will sometimes rot unless 

 allowed to dry for eight or ten days before setting. 

 This is doubtless due to the attack from soil fungi, 

 which readily enter the fresh wounds and find suitable 

 foods for growth. 



Wilt. This disease causes a loss of colour, the 



