Vol. III. No. 48. 



THE AGRICULTURAL NEWS. 



53 



COTTON. 



i 



Cotton Disease in Montserrat. 



The following is the report of Mr. H. A. Ballou, 

 B.Sc, Entomologist on the staff of the Imperial 

 Department of Agriculture, on his investigations 

 relating to the leaf-blister mite which has been causing 

 so much damage to cotton in Montserrat : — 



During ray stay in Montserrat I visited cotton fields in 

 all districts of the island with the view of obtaining any new 

 facts as to the jiresent distribution, the iirobahle origin, and 

 the seriousness of the infestation in different localities. In 

 addition, a considerable share of my time was spent at 

 Dagenham estate and vicinity and at the Grove E.\i>eriment 

 Station, studying the development of the disease since my 

 previous visit and devising and arranging the details of 

 systematic experiments for its control. 



Dagenham estate is on the leeward side of the island ; 

 here where the leaf-blister mite was first noticed, the damage 

 from its ravages has been more serious by far than in any 

 other part of the island. Mr. Watson, the Attorney, informed 

 me that the yield of cotton from 130 acres will be no more, 

 and probably considerably less, than that obtained from 30 

 acres the previous crof). In several fields the cotton was 

 being up-rooted and burned. These fields, under normal 

 conditions, should have gone on bearing for two months 

 longer. At Dagenham there was a serious outbreak of the 

 cotton worm in October, and in several large fields all the 

 leaves were eaten otl" except those which were attacked by 

 the leaf-blister mite. These mite-infested leaves were so 

 distorted and deformed that they were of no use to the 

 plants, and the mites from them infested the new leaves as 

 fast as they were produced, making it especially difficult for 

 the plants to recover. On other estates, fields, which were 

 entirely defoliated by the caterpillars and which were not 

 infested by the mite, made good recovery, and at the time of 

 my visit gave promise of fair crops. The fields that were 

 first attacked sutfered most or they were completely destroyed 

 first. 



On the windward side of the island the leaf-blister mite 

 is to be found in nearly every field of cotton. At Trants, 

 fields,_ which were in bearing and were slightly infested at 

 the time of my visit in September, had in Junuary just 

 finished an excellent crop. I was informed that these fields 

 would soon be cleared and the plants burned without any 

 attempt to produce a ratoon crop. Certain fields at Bethel 

 and Whites are infested but only in spots, and these spots for 

 the most itart are on the windward side of each field. 



In the northern part of the island several fields of 

 cotton were visited belonging to the Jlontserrat Lime Juice 

 Company. These were slightly infested in each case, and as 

 in other cases, nearly always at the windward side of the 

 field. In the south part of the island the same condition 

 was found, the infestation was slight, and on the windward 

 side of each field, showing that the pest had been carried by 

 the wind, and indicating that the mite in each case comes from 

 outside the cotton field. 



One of the most common of the Montserrat wild 



plants is the shrub known as Acacia arahica This 



plant is very seriou.sly infested by a mite, which causes 

 small, sub-globular galls on the leaflets and peculiar, 

 irregularly shaped blisters on the young tender wood 

 of branches and newly formed sjtines. The mite is very 

 similar to the mite of the cotton, but a little smaller (see 

 West Indian Bulletin, Vol. IV, p. 282). The galls on the 



leaflets are not at all like those on the cotton leaf, but where 

 the wood is attacked, very much the same effect is produced, 

 as that noticed on the tender stems of cotton. It frequently 

 happens that several galls occur upon a single leaflet and 

 sometimes on Itoth upper and under surfaces. 



The galls are generally distinct and do not run together 

 to form irregular, distorted masses, excei>t upon the stems 

 and spines where they frequently occur. 



At Dagenham, there are no Acacias growing very 

 near the cotton fields in which the Eriophyes was first 

 discovered, but in every case of recent infestation, as noticed 

 at this visit, infested Acacias occurred in greater or 

 less numbers to the windward and generally at a very short 

 distance. In s\nie of these facts it is not possible to say 

 definitely that this mite has come from the Acacia to infest 

 the cotton. . . . 



The remedies for the cotton leaf-blister mite are still in 

 the experimental stage. The experiments, which were 

 commenced at the time of my visit to Montserrat in 

 September, were discontinued on account of unfavourable 

 weather conditions. Mr. .Jordan, however, carried out some 

 experiments along similar lines, and his results indicate that 

 a mixture of lime and .sulphur in equal parts, dusted on the 

 plants, will help to control the pest. During this recent visit 

 to Montserrat I arranged fcr two series of experiments, which 

 should give more conclusive evidence as to the value of 

 ditferent in.secticides in controlling this i>est. One of these 

 is a field experiment, for which ]\Ir. C. Watson kindly 

 provided i acre of land, which he had put in good condition 

 for planting, and he promised the necessary labour for 

 planting and for the application of the insecticides. The 

 other series consists of several box experiments at the Grove 

 Exiieriment Station. Mr. Jordan has undertaken the 

 supervision of these, as well as the infestation experiment. 

 It is hoped that these experiments will give results 

 sufficiently definite to be of service in the preparation for 

 the next crop of cotton. A report giving details of the 

 exiierinients, the observations, results and conclusions, will 

 probably follow in due course. 



Nothing has been added to the knowledge of the 

 life-historj of Eriophi/es (jouypii during this visit. The 

 working out of this life-history would re(piire several weeks 

 of continuous investigation, and knowing that the necessary 

 time was not available for this purpose, I devoted myself to 

 the investigations as given in the preceding i)aragraphs. 



The following is a brief summary of this report 

 with some conclusions that may be of more or less interest : — 



(a) The cotton leaf-blister mite has increased in severity 

 in those fields, where it was already establfshed, and has 

 appeared in the cotton fields in all parts of the island. 



(b) The attack of the cotton worm greatly added to the 

 injury by the mite in badly infested fields. 



(c) The appearance of the mite in recently infested fields 

 indicates that it may have come from the common wild 

 Acacia. 



(d) Weather conditions, during the past season have 

 been rather unfavourable to the cotton, and consequently it 

 sutfered more from the attacks of the pests. 



(e) Considerable time is required after infestation before 

 the attack becomes a menace to the crop. Ordinary 

 conditions of clean culture and the careful destruction of all 

 plants growing in cotton fields, at the end of the crop season, 

 will probably keep the pest within reasonable bounds. 



(f) Experiments now in progress should demonstrate 

 remedial measures of value in the cultivation of succeeding 

 crops. 



