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THE AGRICULTURAL NEWS. 



December 30, 1916. 



FUNGUS NOTES. 



THE FUNGUS ON CACAO THRIPS. 



Eeference has been made in this .Journal (Vol. X\ , 

 p. 110) to a fungus collected on cacao thrips {Udiothrips 

 rubrocincta) m St. Vincent by Mr W. N. Sands, Agi icultural 

 •Superintendent in that island. It was then stated that the 

 fungus has every appearance of being parasitic, being found 

 •on larvae as well as adults under circumstances which suggest 

 no other cause of death. It occurs as a white mould on the 

 body of the insect, attaching it lightly to the leaf. Under 

 a strong lens the conidia are seen in small globular mas.ses, 

 heaped up on the insect or strung on hyphae around it. 

 Further material having been recently forwarded by 

 Mr Sands, specimens were submitted to Professor Roland 

 Thaxter, of Harvard University, who has kindly replied as 

 follows: ' I have examined the fungus on thrips commu- 

 nicated by Mr. Nowell and am able to confirm his opinion 

 that it is Sporotridium glohxdifi'rum, a very general parasite 

 among insects, although I have not seen it previously on this 

 type of host.' 



The fungus named has had a great deal of attention 

 paid to it in the United States as the cause of an epidemic 

 disease of the wide-spread and serious pest known as the 

 chinch bug (Blissus leiicopterux). 



It was first described by Spegazzini, from material occur- 

 ring on the dead bodies of beetles in Argentina. In the United 

 States, a number of species of beetles, Lopidopterous larvae, 

 and various other insects have been found to be susceptible to 

 attack. Its effects on the chinch bug under favourable condi- 

 tions are very striking. 



'Going to the place in a field (generally a wheat field) 

 where the fungus has been introduced, the track of the chinch 

 bugs as they moved in any direction was in many cases almost 

 literally paved with the dead bugs more or less enveloped in 

 their winding sheets of white. Along ravines, dead furrows, 

 or other depres.sions, the ground would be nearly white, the dead 

 diminishing in numbers as the higher grounds were reached, 

 though these were by no means free from corpses. In one 

 instance the bugs had left a field of wheat at harvest, the 

 .Sporotrichum having been applied there before the move- 

 ment began, and entered an adjoining corn field. The way 

 was marked with white, not only the surface of the ground, 

 but on stirring up the mellow soil of the edge of the corn field 

 it was tVmnd to be literally full of dead chinch bugs to the 

 depth of 2 or 3 inches, the white fungu.s-covered bodies 

 , strongly contrasting with the black colour of the rich loam. 

 Not only this, but under the sheaths of the leaves and on the 

 leaves themselves hundreds of dead were to be found on the 

 outer rows of the corn, on the grass and weeds, and, indeed, 

 almost everywhere Millions of chinch bugs were certainly 

 destroyed in this one field.' (F. M. Webster, Bulletin (lit, 

 United States Bureau of Entomology, page 5.5.) 



As affording the most con.spicuous e-xample of the exploita 

 tion of a fungus as a remedy for an injurious insect, and for the 

 evidence afforded as to the limitations of this type of control, 

 it may be of interest to refer to Bulletin 107 ofthel'nited 

 States Bureau of F.ntomology, by Professors F. li. Billings and 

 P. A. Glenn, which deals with the results of the artificial use 

 of this fungus against the chinch bug in Kansas. 



In Juno lSt35 during moist warm weather an epidemic 

 was noticed amongst chinch bugs in a locality in Illinois .so 

 severe that in a few weeks scarcely one in a thousand of the 

 vast hosts of young bugs observed in the middle of .Tune 

 remained alive. 



The idea of a fungus para.site was at that time ridiculed 

 by the most authoritative American entomologists, but 

 confirmation was afforded nearly twenty years later when 

 a species of Kmpusa was found to be killing off chinch bugs 

 in several localities, and the fungus under notice was found 

 on the same host in five states of the Union. 



Experiments in the dissemination of the fungus were 

 soon begun, both with dead in.sects and with cultures on 

 a mixture of beef broth and corn meal. 



Being followed by severe epidemics amongst the insects 

 in various localities they were considered to have been very 

 successful. In 1 890 chinch bugs in Kansas were very scarce, 

 having been very generaHy exterminated in the previous year. 

 It was, however, doubtful how far artifical distribution was 

 responsible for the outbreaks of the disease. 



In 1891 the University of Kansas was directed by the 

 legislature to propagate the fungus and distribute it free of 

 charge, and some forty to fifty thousand packages of infected 

 material were sent out. The method became popular in 

 other States and distribution was continued for several years. 



Doubts as to it.s efficiency began to be expressed by 

 competent authorities, and in time the practice of artificial 

 distribution was abandoned. It was found that when the 

 conditions were favourable in respect of temperature, humidity 

 of the air, and abundance of the insect, the disease appeared 

 and did great execution whether the fungus had been artifi- 

 cially introduced or not, but that when the conditions were 

 unfavourable no amount of artificial distribution would 

 produce effective re.sults. 



The results of exhaustive experiments made by the 

 authors of the bulletin quoted confirmed these conclusions. 

 They found moreover, that the fungus was present in the soil 

 of the infested area in such abundance that artificial distribu- 

 tion was quite unnecessary. 



The extent of the occurrence of the fungus on the cacao 

 thrips in these islands, and the possibilities of increasing its 

 range and efficiency, are matters for investigation. It is 

 hoped that search will be made in suitable situations, and 

 any suspected material forwarded through the local agricul- 

 tural officers for examination. The fungus is very easily 

 cultivated, and some experiments are already being made in 

 its distribution. 



W.X. 



MULCHING SUGAR-CANE. 



While Cuba seems to have the monopoly of producing 

 sugars more cheaply than any other country in the world, 

 still it is done with an enormous outlay of capital, and done 

 in competition with other tropical countries that apparently 

 spend less money in sugar production than do the Cubans, 

 and this naturally leads to an inquiry— why it is so. The soil 

 and climate of Cuba, as far as they have been exploited in 

 the sugar industry, are extremely, well adapted to sugar 

 production, and the supply of land has been so plentiful and 

 the prices of land so moderate, that the great sugar producers 

 have been disposed to gather crops of sugar-cane from certain 

 lands say for a generation, and then to abandon the old fields 

 for new ones that they have had in course of preparation, 

 and thus go on from decade to decade, eane, as reported to 

 us years ago becoming unprofitable on the north side at the 

 end of eight year.s, and then requiring replanting and becom- 

 ing unprofitable on the south side in twelve to fifteen j'ears, 

 and then becoming unprofitable, or at least less profitable 

 than to replant the same fields again and to get larger crops 

 that would more than pay for the difference in cost. 



