41 



erroneously called, is a malady which frequently causes serious 

 damage. The fungus producing it is of saprophytic habit, de- 

 riving its nourishment from the sweet fluids (honeydew) secreted 

 by certain insects, the attacks of which it invariably follows. 

 As the honeydew falls it strikes principally on the upper sur- 

 faces of the leaves and exposed branches and upper portions of 

 the fruit (the stem end, as the fruit are pendulous), and it is 

 on these portions that the sooty mould grows. It developes 

 also to some extent on the lower surfaces of the leaves, but is 

 not so abundant here. In Florida sooty mould follows princi- 

 pally the attacks of the mealy wing or white fly (Aleyrodes 

 citri, R. & H.) wax scale (Ceroplastes floridensis), mealy bug 

 (Dactylopius citri) orange plant louse or aphis (Aphis gossipii, 

 Grlover), &c, and spreads as these insect pests spread. It is 

 only where it follows the mealy wing, however, that it becomes 

 serious. In this State it is estimated that the loss it causes is 

 not far short of $50,000 annually. 



Besides occurring on all varieties of citrus fruits, sooty 

 mould is frequently found on a number of wild plants in 

 Florida. It is particularly abundant on a gall berry (Ilex 

 glabra) red bay, (Persea carolinensis), which also infests the 

 orange. 



Sooty mould is probably common in all orange countries of 

 the world. In California it causes much damage and is con- 

 sidered a serious malady. There it follows chiefly the black 

 scale (Lecanium oleae) and the cottony cushion scale (Icerya 

 purchasi). In Louisiana it is very common on the orange, 

 following chiefly as in Florida the mealy wing and wax scale. 

 It is also quite common in Spain, Italy, and many other orange- 

 growing countries (3). 



Symptoms — Sooty mould may be readily recognised by the 

 dense sooty black membrane which it forms over the fruit and 

 upper surfaces of the leaves. This membrane is made up of 

 the densely interwoven branched mycelial filaments (threads) 

 of the fungus, the individual filaments of which can in some 

 cases be distinguished with a hand lens. When isolated the 

 filaments are seen to vary in colour from olive green to dark 

 brown. They are at first loosely interwoven, but gradually 

 become very numerous and crowded. Finally they become 

 cemented together, forming a dense compact membrane. The 

 fungus as nearly as can be determined, is entirely superficial. 

 Small projections occur on the filaments, but no proof has been 

 found that these penetrate the tissue of the leaf. Apparently 



(3) In Jamaica it is common on the Rose Apple, Eugenia Jambos, 

 Linn. 



