154 



THE AGRICULTURAL NEWS. 



May 17. 1919. 



INSECT NOTES. 



Chinch Bug Fungus. 



The following letter to the Imperial Comiuissioaer of 

 Agriculture for the West Indies has been received from 

 Mr. T. Jackson, the Curator of the Botanic Station, An'igna, 

 transm tting cotton stainers supposed to have been killed by 

 a funj5us- This is of general interest : — 



'I am forwarding to )0U under separate cover some 

 dead cotton stainers. These were obtained from under a mahoe 

 tree growing in the Botanic Station. The tree in question had 

 very many insects some w eks ago, but although young 

 stainers are still somewhit abundant on it, there aro only 

 a limited number of adults. 



'A number of the insects s' nt are covered with mycelium 

 which, possibly has been the cause of death. As many 

 dead insects (adults and half grown) are to be found under 

 the tree in question, it would seem a? though this fungus 

 or some other control, is at present keeping the pest in 

 check.' 



The fungus has been identified by Mr. W. Nowell, Mycolo- 

 gist on the stafif of the Imperial Department, as Sfiorotrichum 

 glohuliferum, a parasitic fungus on insects of wide distri- 

 bution. It has been found attacking thrips of cacao in St. 

 Vincent and Grenada, as was noticed in the Agricultural 

 Newf, Vol. XV, p. 430. and it is also well known as an 

 important natural enemy of the chinch bug in Kansas and 

 other localities in the United States, where it has 

 been a serious pest of corn, wheat, and other cereals for 

 many years. 



This is the first record of any coniriderable numbe- of 

 cotton stainers being found dead around their food plants 

 in thf West Indies, and it would appear that the 

 conditions are not often favourable for such an 

 attack as this one. At tho same time it must be 

 stated that the campaign which is now being carried out 

 against the wild food plants of the stainers is resulting 

 in more attention being paid to these insects in relation to 

 snch pi nts as the mahoe, or .John Bull (Thes/xsi'ii populnea) 

 than wa.s formerly the cast,-, and it is posible that previous 

 to the initiation of the campaign such an attack might have 

 passed unnoticed. It must also be pointed out, however, 

 that in St. Vincent attention has been directed to the relation 

 of stainers to their wild fo d-plants for .several years, and 

 that this fungus has been known for some time to occur in 

 that island, and yet no attack of the fungus on the stainers 

 has been previously reported. 



In past seasons cotton .'!tainer3 have occurred in large 

 numbers in almost all the islands where cotton is grown, and 

 there have been sudden disappearances of the insects. Sume- 

 timeathey have flown away from the cotton fields in swarms, 

 as for instance during the cotton season just passed in St. 

 Kittsand Nevis. At other times they have disappeared with- 

 out any observations being icported as to how and where 

 they went. If in such a case as the latter the stainers had 

 been killed by a general attack of fungus, it is to he expected 

 that the dead insects would have been found in sufficient 

 numbers to attract attention. 



The fungus is easily cultivated in an artificial medium, 

 such as dour paste, with a little meat extract added, and it 

 is hoped thit trials will be made to sec whether any good 

 results can be obtained by a distribution of the fungus 

 directly to the field, or by infecting stainers in the 

 laboratory and liberating them in the field. 



In Kansas, where perhaps the greatest amount of work 

 of this kind has been done in the employment of this fungus 

 for the contr>l of the chinch bugs, it has been decided that 

 if the fungus is present in any locality, its natural spread 

 provides the mixirauni of its efficiency, and that nothing is 

 to be gained by artificial distribution. 



The subject is thoroughly discussed in Bulletin No. 191 

 of the Agricultural Experiment Station of the Kansas Sta'e 

 Agricultural College, issued November 1913, with regard 

 to the conditions of temperature and humidity, seasonal reac- 

 tion, and all other conditions affectinu 'Co.". inter relation of the 

 insect and the parasitic fungus, as these occur in the State of 

 Kansas. The following aeneral conclusions are expressed:—- 



'We therefore hold that the facts of the life economy of 

 the chinch bug and of the chinch bug fungus, and evi- 

 dence of properly conducted experimental tests unite in show- 

 ing that artificial distribution of the chinch bug fungus, 

 either on diseased bugs or on artificial cultures, is not worth the 

 time and trouble that it takes.' 



The conditions in these West Indian islands are not the 

 same as those in Kansas, nor are the habits of the cotton 

 stainer, the insect to be dealt with, the same as thosp of the 

 chinch bug. While therefore a careful trial of the artificial 

 spread of the fungus is worth being made, in face of the con- 

 clusioDB reached in Kansis too much must not be expected 

 from such an experiment. H..4..B. 



THE M/^HOE OOOHON TREE IN RELA- 

 TION TO COTTON STAINER CONTROL 

 IN ST. VINCENT. 



The lollowino; notes, contributed by the Agri- 

 cultural Superintendent St. Vincent, Mr, W. N. Sands, 

 are of special interest at the present time with 

 reference to the appearance of the chiiich-bug fungus 

 in Antigua, as reported in the preceding column. 



They also afford another proof of the careful 

 investigation into the control of cotton stainers that is 

 being conducted in St. Vincent by the officers of the 

 Agricultural Department there: — 



The 'Mahoe cochon' or 'Dobaruboia' (Douve bois) tree 

 {S/iircu/ia caribaca) occurs in the mountain forests at the 

 northern end of St. Vincent at elevations between 800 and 

 l,500Teot. It Ins been described by tlie writer in relation 

 to the local cotton stainer (Dvsde}cus (Maiinevi, Leth.) in the 

 West Indmn Bii//eti>i, Yo].'\yi, [>p. -249 50. In the cam 

 piigns ayninst the fooil-plants of the pest during the past three 

 seasons, this tree was not destroyed, although the cotton stainer 

 was known to feed and breed on its seeds. The reason for this 

 was that from extended observations it appeared that, 

 although the insect wis attracted to the tree in the dry 

 months of March and April each year, yet few apparently 

 survived the unfavourable conditions of the wot forest in the 

 succeeding months cf very heavy rainfall. Further it was 

 considered that the cotton stainer was essentially an 

 inhabitant of the coastal districts or lands at low elevation 

 with a relatively dry climate, because its chief food plant.>i, 



