126 



THE AGRICULTURAL NEWS, 



April 8, 1916. 



DISEASES OF PLANTS. 



THE INTERNAL DISEASE OF COTTON 

 BOLLS. 



In continuation of tlie articles on the above subject 

 published in this Journal, Vol. XIV, pp. 222 and 238, the 

 following further information is now given. 



Mr. W. Bobson, Curator of the Botanic Station, 

 Montserrat, carried out some further experiments during the 

 past season to test the connexion of cotton stainers with^ the 

 disease. Two muslin cages were used, erected over single 

 plants in a field from which stainers appeared to be absent. 

 In the one cage stainers in large numbers were confined, from 

 the other they were excluded. Two trials were made, one 

 in August and one in September, with the following results: — 



Duration of first experiment ten days, of second fifteen 

 days. 



With regard to the badly diseased boll in the second 

 e.xperiment, Mr. Bobson stated his belief (since confirmed) 

 that the green bug Neinr<i viriduhi is capable of originating 

 the disease, and suggested that the boll may have been punc- 

 tured by this insect before enclosure. 



In '.January 1916, the following experiments were carried 

 .lut at the St. Vincent Experiment Station by Mr. S. C. 

 Harland, B.Sc, Assistant Agricultural Superintendent. 



EXPEKIMENT. 1. 



Six plants from a plot of Sea Island cotton with 98 per 

 cent, diseased bolls had the bolls removed. Three were placed 

 under a muslin cage and three were left uncaged. Three 

 ■weeks later the bolls from each plant were examined. 



RESULTS. 



Caged Plants. 



Uncaged Plants. 



Experiment 2. 



A Brazilian cotton was selected which was growing in 

 an isolated po.sition. There were no stainers on the plant 

 and an examination of fifteen bolls showed that no internal 

 boll disease was present. 



Ten of the remaining bolls were enclosed in muslin bags. 

 In five of the bags a pair of stainers was imprisoned. The 

 bolls were examined ten days later. 



RESULTS. 



Bolls with stainers. 4 showed definite disease. 



1 ,, proliferations with doubts 

 ful disease. 

 Bolls withoul .stainers. All 5 were quite healthy. 

 Bolls from both the Montserrat and St. Vincent series 

 of experiments were preserved and forwarded to this ( )ffice 

 for examination, and the disease found to be due to the- 

 specific fungus mentioned in the previous article. All the 

 facts ascertained point to the conclusion that the disease is 

 either carried by, or supervenes upon the attacks of plant- 

 feeding bugs. 



Early in January this year the writer found bolls with 

 the same affection on a self-sown plant of the perennial type 

 growing on waste land in Barbados. Cotton stainers are not 

 found in Barbados, and there is no such return of stained 

 lint as occurs in the case of the other islands. 



On the plant referred to, a few adult green bugs (Ne\iir>t) 

 were present. When these soon afterwards disappeared the 

 new bolls ceased to become affected, but the disease reappeared 

 as a new brood developed. A period of cessation of growth 

 and defoliation, due to drought, followed and caused the 

 dispersal of the bugs, and the abundant new shoots and bolls 

 now on the plant are free from bugs and from disease 



During the recent Cotton Conference in St Kitts, Mr. 

 Harland found internally discoloured bolls on a plot of out-of- 

 season cotton in that island, and the examination of these 

 has revealed the presence of the characteristic fungus. 

 There is a fair proportion of stained cotton produced each 

 year in St. Kitts, but no instance appears to be known 

 of the second picking being practically all affected, as has 

 been the case from time to time on estates here and there in 

 Montserrat and St. Vincent. There appears to be a general 

 agreement among cotton planters that the amount of staining 

 experienced is not at all proportional to the number of 

 stainers present, a nuraerou.s infestation sometimes resulting 

 in a smaller amount of stained lint than is produced under 

 certain circumstances when stainers are comparatively few in 

 numbers. The latter condition was well illustrated at the 

 St. Vincent Experiment Station in December of last year. 

 This indicates the necessity for taking the fungus into account 

 as well as the insect, since it seems probable that the dispro- 

 portion is due to the effect of the prevailing conditions upon 

 the former factor. 



It is hoped to obtain by experiment more exact informa- 

 tion on the outstanding points with regard to this affection 

 during the next cotton-growing season. 



The fungus concerned has very considerable scientific 

 interest owing to its methods of spore formation. It has 

 now been found in material from Tortola, St. Kitts, Mont- 

 serrat, St. Vincent, and Barbados. It occurs in nearly all 

 the bolls examined, but as indicated in the previous article, in 

 a small proportion it is replaced by bacteria. 



The fungus resembles very clo.sely Eiriaothiciuni fymhal- 

 ariae, Bor/i, found in Italy in 1888 in the capsules of 

 Linarid i-ynihularid by Borzi, and again in France (1906-12) 

 in the fruits of an rmbelliferous plant (Carhri/f hicpignta) 

 by (!. Arhaud {Bull, de Soc. Xfi/col. tie France, X.XIX,, 

 572-5). In addition to the sporangia described by Borzi, 



