170 



THE AGKlOaLTURAL NEWS. 



May 25. 1912. 



INSECT NOTES. 



A DISEASE OF GRASSHOPPERS. 



The last volume of the Aijricultural News contained on 

 page 410 an article describing work that had been carried 

 out, in Yucatan, which showed that a disease germ known 

 to produce fatal results in grasshoppers could be employed in 

 the control of this pest. Subsequently, another article has 

 appeared in the Journal d' Agriculture Tropicale for March 

 1912, p. 70, which states that the study of the disease has 

 been continued at the Pasteur Institute, on the return to 

 France of the investigator, M. d'Herelle. 



A further phase of the same matter receives interesting 

 description in the article that has just been quoted. At the 

 end of last December, the Argentine Government obtained 

 the services of M. d'Herelle for the purpose of enquiring if it 

 •was possible to undertake the destruction of grasshoppers, 

 which are serious pests in parts of the Republic, by employ- 

 ing the disease for the purpose. The importance of the 

 matter was all the greater because of the existence of areas 

 in Argentina which it seems to be impossible to colonize on 

 account of the periodical appearance of the scourge. Past 

 efforts have been made to devise means for lessening the 

 damage done by the pest, in this country, and there exists 

 a commission and a bureau organized for the service, but it 

 was desired, nevertheless, to invoke the services of the 

 investigator mentioned. It may be said shortly that, as in 

 Yucatan, the results of the work have been eminently 

 successful. 



The first care of the investigator was to increase the 

 virulence of the bacillus responsible for the disease, by means 

 of successive inoculations of the insects When the maxi- 

 mum degree of virulence had been gained, pure liquid 

 cultures were prepared and were used for infecting flights of 

 grasshoppers. 



The first trials were made with insects in captivity, 

 which were allowed to feed on alfalfa on which a small 

 amount of the culture had been spread. After forty-eight 

 hours, the mortality was aboat 50 per cent.; in five days all 

 the insects were dead. Further, the microbe of the disease 

 was found to be almost the only bacterial organism present 

 in the intestines of the dead insects and in the liquid 

 excreta found on the alfalfa. At the end of such absolutely 

 convincing experiments, practical trials were made in diff- 

 erent parts of the country! 



On January 16, a flight of grasshoppers was enclosed, by 

 means of barriers made of corrugated iron, in a space having 

 an area of about 1 1 acres, and nearly 1 pint of a culture of the 

 bacillus was spread on the ground. In four days, 75 per cent. 

 of the insects were dead, and after a second similar period they 

 had all succumbed. 



On January 18, a meadow having an area of 88 acres, 

 where there was a large number of winged grasshoppers, was 

 infected with 1 f pints of the culture, which was scattered broad- 

 cast. Five days afterwards, an enormous number of dead and 

 dying insects was found all over the meadow and in the sur- 

 rounding wood. 



Several days after, over •"> pints of the culture was 

 scattered in areas infested by grasshoppers. On the following 

 day, numerous dead insects were found, and the plants were 

 soiled by excreta. All the flights which passed the infected 

 region, and which rested there, were contaminated; and within 

 a radius of several mile.s, dead grasshoppers were found. 



Actually, about one million of the dead insects was observed 

 on each acre. 



Other experiments have shown identical results, and it 

 has been found that if the insects are infected through the 

 stomach, by eating contaminated plants, they die in a time 

 which varies from eight to twenty-four or thirty-six hours. 

 The effect is increa.sed by the fact that the excreta contamin- 

 ates fresh plants, and a further destruction of insects is 

 caused 



Toward the end of the article, it is claimed that the 

 experiments described place beyond doubt the efficacy of this 

 means for the destruction of grasshoppers. As the matter 

 aro.se from observations made of a disease of the insects in 

 Y'ucatan, occurring in a species identical or nearly related to 

 that of the Argentine (Schistocerca americana), there may 

 have been the fear that special conditions may not have per- 

 mitted an easy development of the disease among the South 

 American insects. Happily, this fear has not been justified; 

 on the contrary, even non-migratory grasshoppers have been 

 found infected. It seems that the extreme virulence of the 

 bacillus producing the disease (Coccobacillus acridorum) 

 should ensure its usefulness among the most diverse species. 

 At any rate, it is easy to make experiments to determine the 

 matter. 



THE BANANA WEEVIL BORER. 



In a letter received recently by the Imperial Commis- 

 sioner of Agriculture from Mr. Frank P. Jepson, Government 

 Entomologist of the Fiji Department of Agriculture, enquiry 

 is made as to methods of control known to be of value in 

 dealing with the banana borer. 



This insect, which has been recorded as a pest in 

 Dominica in previou.s years, under the name Sphenophorus 

 sordidus, German, is stated to be the same as Cosmopolites 

 sordida, Chevrolat. It is said to be a serious pest of bananas 

 in F)ji, and to defy all artificial methods of control Mr. Jepson 

 proposes to visit certain islands in the East Indies, with the 

 object of endeavouring to discover some efficient parasites of 

 this borer which are supposed to exist there. 



The banana borer has not occurred in sufficient numbers 

 in the West Indies, during the past nine or ten years, for it to 

 have been recorded as a pest during that time. It would be of 

 interest, however, to know whether any planters have observed 

 borers in the stems of banana plants, just above the ground, 

 and also how much damage may be attributed to this pest. 

 There is, of course, a possibility that efficient natural enemies 

 of the borer exist in the West Indies, and that they prevent 

 its increasing to sufficient numbers to become a pest. In any 

 case, it would be useful for any observations, that may be 

 made on this insect, to be communicated to the Imperial 

 Department of Agriculture. 



The Cotton Boll Weevil.— In the Cuba Magazine 

 for January 1912, a short account is given of trials in grow- 

 ing cotton in a district where the cotton boll weevil is known 

 to occur, for the purpose of ascertaining whether cultural 

 methods can be depended upon to prevent attacks by this 

 pest. The result of these trials, so far, has been that by 

 late planting —after the season of greatest abundance of 

 insect pests— and the immediate destruction of all old plants 

 and trash when the crop is finished, cotton has been grown 

 fur three years without any sign of IjoU weevil attack. (See 

 also Agricultural iVeo-?, Vol. XI, p. 121.) 



