318 



THE AGRICULTURAL NEWS. 



S] ii i MB] i: 25, 1915. 



FUNGUS NOTES. 



DISEASES OF CITRUS IN THE ISLE OF 

 PINES. 



We Li- the i'ir-t Annua] I May 



1915, of tho ' I Laboratory, San Pedro, [sle 



ell any, 



( lolumbus, Ohio. The [sle of Pi 



I thai island. 



An inn >j Mr. I'. S. Earle, formerly i >in 



I Lgronom Cuba, suj plii tl ii u i that 



the Growers Association have over 1,200 acres of citrus 

 trei ruit, al San Pi dro. Planting was begun 



In i he spring ol I 9 



When the fruil began to be shipped there were very 

 serio ad in 1914 Mr. Earle 



wa hi i" advise on this and othei questions. Be 



reports that the fruit was from young trees thai had not 

 pi iperly balanced fruiting fertilizer (it is to be 

 feared thai a good many trees in the West [ndies have to go 

 through life without this luxury), that the picking and 

 shipping were done during verj wet weath< r, that no proper 

 packing facilities were available, and thai the fruit was 

 subjected to much rough handling in transit. Without 

 questioning the author's dictum that all these unfavourable 

 factors combined would not cause the rotting of fruit except 

 for the presence of some rot producing organism, or his 

 statement that until this organism or organisms had 

 definitely determined and critically studied any proposed 

 remedial measures could onlj be empirical, it might well be 

 asked whether the application of any amount of taxonomie 

 and physiological research would prevent the fruit from 

 rotting in one way or another under such circumstances. 



A privately maintained pathological laboratory was 

 established for the investigation of this and other troubles, 

 with Mr. John M. Rogers as investigator under the direction 

 of Mr. Earle. The results already achieved are regarded as 

 amply justifying the expense involved. 



The report includes notes on a number of insert pests 

 and of various affections of trees and fruit. The longest 

 article, on the subject of 1 >iplodia diseases, has special interest 

 as dealing with a condition which has also come under notice 

 in Montserrnt. The discussion of witbertip is of interest for 

 similar reasons. 



The latter article throws some light on a question which 

 has been something of a puzzle to the present reviewer. The 

 literature of citrus diseases in America from 1901 onwards 

 contains frequent references to Col.'etolric/iuni ylo'osporioides 

 as the cause of die-back of twigs of citrus trees, spotting of 

 the leaves and fruit, and dropping of flowers and young fruit. 

 But although a fungus apparently answering to the descrip 

 tion of * 'o letotrkhwm gloeospori aides is universally distri- 

 buted on dead twigs of lime trees in the Lesser Antilles, and 

 has occasionally given evidence of ability to function as 

 a weak parasite in such situations, do such damage to leaves 

 and fruit as is described in America has been in evidence. 

 Earle and Rogers now state with regard to Colletotrichvm 

 gloeosp'.rroid'*: 'According to but observations and experi- 

 ments her.- it is strictly a saprophyte, and has little or no power 

 to attack living tissues. It is everywhere present in the 

 groves, occurring abundantly on dead tissue of leaves, twigs 

 rod fruits, but in none ol oi ttions has it been able to 



produce a specific disease.' The writers go on to say that 

 t he earlier authors seem to have confused the effects of this 

 fungus with those of anothei Colletotrichum (of the lime) 



which is I species alsi ■ occurs in the 



[sle ol Pines' on 'the native lime, causii - the 



1 serious blasting of the flowers and young twigs 

 and the distortion and dropping of the fruits.' Apparently 

 we have the first Fungu I >nd in the Lesser 



Antilles whichever} effort should to 



maintain. (It is nql clear what plant is referred t< 



ive' lime. ST< 

 to the New World Apparently the word is used it 

 equivalent to 'locally establish 



The Diplodia disease to which an allusion is mad 

 is caused by a fungus which the writers regard as then most 

 serious citrus enemy. It attacks trunk-, tw and 



causes the onlj destructive rol ol the mature fruit. 'A dying 

 back of the branchi illy on trees on unfavourable soils 



andal the beginning , of the drj season, has long been knowt 



( luba and the Isle of Pini is citrus tro I 



Our investigations show, very clearly, that it is caused by 

 this Diplodia fungus, and we are the Diplodia 



Die-back.' It 'doe, not attack u rowing tissues, hut 



when growth suddenly stops from any cause, as from tin 

 setting in of a sharp period of drought, many twigs may be- 

 come infected.' Fruit is att icked on the tree, and infects the 

 twigs on which n is borne. The disi ise ma} be -elf-limited 

 tonne limb, or may in other circumstances kill the trunk 

 itself. 



In seeking to remedy the dis< ise, beyond cutting out 

 diseased limbs, chief reliance must be placed on such cultural 

 methods as will keep the trees in a thrifty growing condition. 

 Limbs weakened by scale are regarded as particularly subject 

 to die-back, and the white scale {Chionaspii) by causing 

 cracking of the hark often leads to infection. 



The specific identity of the fungus has not been deter- 

 mined, but it has been found to be somewhat widely distri- 

 buted on other tropical plants. ( >ne might suggest that 

 a comparison be made with Lasiodip/odia theobromae, Griff. 

 et Maubl., the member of the group most familiar in the 

 islands further south, and a species to whose protean character 

 the list of synonyms bear- sufficiently eloquent witness. 



W.N 



DIE-BACK OF LIME TREES IN 

 MONTSERRAT. 



As affording an interesting comparison with the descrip 

 tion reviewed above of citrus branch troubles in the [sle oi 

 Pines, the following extract is published from a report made 

 to the Dmperial Commissioner of Agriculture respecting 

 a recent short visit, to Montserrat : — 



'The factors concerned in i he dying hack of twigs and 

 branches are possibly somewhat complicated, and cannot be 

 determined with certainty by insp tion and the examination 

 of specimens. Observations of the sequence of events during 

 their decline are necessary heforea definite conclusion can be 

 reached. Certain probabilities, however, may be indicated 



' Much of the die-back is complicated by the presence of 

 scale insects on the branches which fail. I was able, however, 

 to find instances where scale insects were practically absent 

 and where there were no indications of their having been 

 present in adequate nuinhers to account for the failure. I 

 regard them in most cases as merely, which 



hasten, but do not cause the death of twigs and branches. 

 I am more inclined to believe that it is usually when tin- 

 branch has already become sickly that they are able to 

 increase to a serious extent. 



