334 



THE AOKiCULTURAL NEWb. 



October 12, 1912 



FUNGUS NOTES. 



'There were ninety-five mangoes in the cases: — 



THREE FRUIT DISEASES AND THEIR 



CONTROL. 



MANGO AND AVOCADO PEAR. At the Agricultural Con- 

 ference held in Trinidad in January last Mr. J. B. Korer 

 presented a paper entitled Some Fruit Diseases, which was 

 subsequently published in the West hidiaii Bulletin, 

 Vol. XII, p. 464. In this paper, among other matters, he 

 dealt with anthracnose or black spot disease of mangoes and 

 avocado pears, and stated that in each case the damage could 

 be controlled by spraying with Bordeux mixture. The disease 

 of the mango is due to a small fungus, Gloeosporium man- 

 giferae, while that of the avocado is probably caused by an 

 allied species. Reference to the presence of the mango 

 anthracnose in St. Vincent was made in the Agricultural 

 Ktfs, Vol. X, p. 190, while the same malady is probably to 

 be found in all the smaller islands; it has been observed very 

 markedly in Dominica, especially on the better, grafted 

 varieties. An anthracnose of the avocado pear is described 

 by Stevens and Hall in Diseases of Economic Plants, p. 184, 

 and is attributed by them to Co/ let of rich ton gloeosporioides, 

 a fungus better known as causing wither-tip of citrus trees. 

 These authors do not state definitely in what locality this 

 disease occurs, and it may not be quite identical with the 

 Trinidad form, but the causative fungi are at any rate 

 closely related. 



In the case of the mango the fungus not only attacks the 

 fruit and leaves but also the Howers and flower stalks. The 

 spots on the fruit are at first about the size of a pin's head and 

 are often arranged in parallfel streaks along the fruit, the streaks 

 representing the course of drops of rain water laden with spores 

 that have fallen from the leaves on to the surface of the fruits 

 and then run off leaving many spores behind to germinate and 

 cause infection. Mr. Rorer showed some excellent photographs 

 illustrating this. The spots rapidly increase in size and run 

 into one another, until finally the whole surface may become 

 discoloured and the rot is found to extend in to the seed. In 

 the case of the avocado pear, the leaves and fruit alone appear 

 to be affected. This disease, though disfiguring, is not very 

 serious when the fruit attacked is used for local consumption, 

 but at once becomes of primary importance when it is 

 packed and shipped for export to temperate countries, as it 

 will develop so strongly while the fruit is in transit as to 

 cause the loss of a large part of the shipment. 



Anthracnose of both host plants can be controlled by 

 careful spraying. In the case of the mango the first spray- 

 ing must be carried out as the flowers open, in order to 

 protect them as well as the flower stalks. Successive appli- 

 cations must be made until the fruit is well set and then 

 they must be repeated when the fruits are half to three- 

 quarters grown, according to the weather conditions. In the 

 case of the avocado, the time of spraying follows closely that 

 of the mango, but the applications need not begin so early. 



To test the possibility of shipping mangoes from Trini- 

 dad and the effect of spraying, a box of sprayed and 

 unsprayed fruit was sent to Mr. A. W. Hill, the Assistant 

 Director of Kew, and according to the minutes of the meet- 

 ing of the Board of Agriculture, Trinidad, held on August 16, 

 the following remarks were contained in the reply, and 

 showed that sprayed mango fruits can be successfully shipped 

 to England in quantity. 



10 

 15 

 22 

 29 

 19 



Gordons 



Divine 



Julie (unsprayed) 



Julie (sprayed) 



(less ripe) 



'A few fruits were .slightly bruised or squashed owing 

 to pressure from the overlying fruit but none were rotten 

 and every fruit was edible. 



'At the date of writing there are still nearly two dozen 

 fruits not quite ripe. 



'We were very much struck with the fine appearanee of 

 the sprayed fruits and they have not ripened so quickly 

 since their arrival as the unsprayed Julies. 



'The fruits which were found to be ripe or somewhat 

 squashed on arrival were as follows: — 



Gordon 1 ripe 



Divine 5 ripe, 1 rather squashed 



Julie sprayed -5 rather squashed 



,, „ (less ripe) 1 ripe 

 ,, unsprayed 1 ripe 3 rather squashed 



'Of the more or less squashed fruits four were rather 

 split but all could be eaten. 



'The fruits have been appreciated by over forty people. 



'The Gordons did not meet with general favour as they 

 have more of the turpentine flavour.' 



BREAD B'EUIT. In the JouDial of the Board of Agriculture, 

 of British Guiana, Vol. VI, p. 14, Mr. F. A. Stockdale describes 

 a di.sease of bread fruit that was found to be fairly common in 

 Georgetown and on the farms of the East Coast of Demerara. 



'The disease commences as small brownish spots generally 

 approximately circular in shape which are to be observed on 

 the surfaces of the bread fruits. On examining this closely, it 

 can be noticed that the centre is generally darker than the 

 edges of these discoloured areas, and it is probable that these 

 darker sunken areas mark where infection took place These 

 discoloured areas become sunken and gradually assume 

 a darker brown hue. They usually measure about H to 2 

 inches in diameter but cases have been observed where they 

 measure up to four inches in diameter. If one of them is cut 

 through it vrill be seen that the internal tissues are also 

 discoloured and present a brownish hue, and they eventually 

 become "water- soaked" and slimy. 



'The disease may affect the breadfruit at any stage of 

 its growth, when the "fruits ' are young or when they are 

 practically ripe. Where only a single spot becomes affected 

 the "fruit'' may ripen and a portion of it can be used, but 

 when the fruits are affected at several points they usually 

 fall before they are ripe, and rot If the disc-^'d areas are 

 examined closely when they are dark-brown iii appearance 

 small pin points of a pinkish grey colour will be seen. These 

 on examination under a lens can be observed to be the spores 

 of a fungus and infection experiments conducted in the 

 laboratory have shown that these spores are produced by the 

 fungus that ia responsible for the disease. Injections that 

 have been made in healthy "fruits" have shown that infection 

 takes place during forty-eight hours, and that within four 

 days the diseased sunken areas had a diameter of 1 ; inches 

 with an internal depth of slightly over 2 inches.. These 

 injections were made under aseptic conditions by means of 

 shallow cuts through the epidermis. How infection takes 

 place in nature has yet to be ascertained.' 



The actual identity of the fungus causing the disease 

 has yet to be worked out, but a species of Gloeosporium is 

 suspected, and with it are associated Fusarium spores whose 

 relation to the disease is undetermined. 



