132 TRINIDAD AND TOBAGO BULLETIN. \ XVIII. 3. 



THE FUNGOUS DISEASES OP THE AVOCADO. 



By James Rirch Roeer, M.A., 

 Mycologist, Board of Agriculture. 



With Two Plates. 



As there are no regularly planted avocado groves in Trinidad iqitO' 

 the present time, but the ti'ees are scattered througli cacao and other 

 cultivation, this fruit has remained fairly free from destructive attacks- 

 of fungous diseases. • 



On account of the recent interest which has been taken in this fruit, 

 and the possibiHty of there being large plantings in the future, leading 

 to an export trade, it is advisable at this time to call attention to the 

 diseases which do occur, and which may at any time become epidemic, 

 as one, at least, has already become in other countries. 



The only serious disease, which has been observed up to the present 

 time, attacking the fruit, is the so-called Anthracnose. This is caused 

 by a fungus, identical, or at least, very closely related to that which 

 causes Anthracnose of the mango, which lias already been described 

 in this Bulletin.-' 



It is almost impossible to buy in the market an avocado fruit which 

 is not attacked by this disease to a certain extent. As the fruit are 

 consumed almost at once, no great amount of damage results from the 

 infections, but if such fruits were packed for export, within a few days 

 they would all become I'otten, and the receiver would only get a crate 

 or a box of avocado seeds in a mass of rotting pulp. All the Antlu-ac- 

 noses do an enormous amount of damage to fruit of various kinds 

 during shipments. 



SYMPTOMS OF ANTHRACNOSE. 



The disease, as it attacks the avocado, appears first as a vei-y small 

 brown spot. If the attack takes place when the fruit is green, the 

 diseased spot ceases to grow and becomes somewhat sunken and the 

 fruit cracks around the margin ; small black pimples may be noticed in 

 the centre of the brown tissue. If the attack is bad, the young fruits 

 fall to the ground prematurely, otherwise, the fruit may reach maturity, 

 but the skin is cracked at the various places adjacent to the brown 

 spots. When soft-skinned fruits are attacked, the fungus penetrates 

 into the flesh and forms a cone-shaped mass of diseased tissue, which 

 may extend all the way into the seed, and gradually rots the whole 

 fruit. When attack takes place on ripe fruit, they rot very quickly, as 

 shown in the figure. 



As in the case of the mango, the fungus also attacks leaves, and 

 causes a certain amount of defoliation. 



'BuU., Dcpt. Aor., Trinidad and Tobago, XIV, 1915. 164. 



