170 



THE AGRICULTURAL NEWS. 



May 23, 1914. 



INSECT NOTES. 



INSEOT PESTS AND FUNGOID DISEASES 

 IN BARBADOS, 1912-13. 



The main body of the Report on the Local Department 

 of Agriculture was reviewed in the last issue of the Agri- 

 cultural News. In the present article that portion of the 

 publication relating to insect pests is dealt with. 



This part of the Report naturally falls into two sections: 

 that prepared by Mr. .J. R. Bovell, I.S.O., Superintendent of 

 the Local Department, and that prepared by Mr. W. Xowell, 

 D.I.C., the Assistant Superintendent. In the first of these 

 sections, there are, in addition to an account of the general 

 administrative work, field and plot experiments and other 

 routine matter, reference to the fumigation of plants and 

 insect pests and fungoid diseases, while Mr. Xowell's report 

 deals with the entomological and mycological investigations 

 carried out by him during the year. 



During the twelve months under review, 497 consign- 

 ments of plants and seeds, other than cotton seed, were 

 examined, of which forty-seven were either fumigated or disin- 

 fected, and 51 were destroyed. The importation of cotton 

 seed for oil extraction amounted to seventy-one lots with 

 a total of 22,128 bags, all of which were fumigated. 



Experiments as to the efficiency of the fumigation of 

 cotton seed with sulphur dioxide showed that this gas did 

 not penetrate more than 3 inches into the mass of cotton 

 seed sufficiently to be effective in killing the insects experi- 

 mented with. This was proved to be due to the absorp- 

 tion of the sulphur dioxide gas by the cotton seed in the 

 outer layers. Trials made with hydrocyanic acid gas gave even 

 less satisfactory results, the depth of penetration ranging 

 from only 2 inches in some cases to 10 inches in others 



In the trials in the use of carbon bisulphide, it was 

 found that this substance penetrated through the cotton seed 

 sufficiently to kill insects in the centre of the bags. The 

 dose was at the rate of 1 dram per cubic foot of space 

 in the fumigating room, which was kept closed for twenty-four 

 hours. The carbon bisulphide was exposed in open dishes in 

 the room, which was kept closed for twenty-four hours. 



The order prohibiting the importation of sugar-cane, etc., 

 from countries where the froghopper is known to exist was, 

 on November 21, 1912, made to apply to the island of 

 Grenada, where a species of froghopper (not on sugar-cane) 

 had been reported to occur. 



Under the heading of Insect Pests and Fungoid Diseases, 

 the Superintendent of Agriculture gives a summary of the 

 efforts to forward Tiphia parallela, the parasite of the brown 

 hard back {Phytalus smithi) to Mauritius, on account of the 

 occurrence of Phytalus smithi on estates where it had not 

 been known formerly, and makes mention of the fact that the 

 leaf-blister mite of cotton had spread to the south-eastern 

 portion of the island where it had not occurred in the previous 

 cotton season. It is stated that the extinction of the cotton 

 industry is feared if no suitable measures for the control of 

 this pest are discovered, unless certain indigenous strains of 

 cotton resistant to the attacks of the pest can be developed to 

 produce good quality cotton in paying quantities. 



This fear does not seem well founded, since in other West 

 Indian islands the leaf-blister mite has been a pest of cotton 

 for the last ten years and cotton has continued to be grown 

 and to produce profitable crops. This has been accomplished 

 by careful plant selection to produce pure strains of early- 

 maturing Sea Island cotton, the picking off of the first-infested 



leaves, and in some instances the complete destruction of the 

 old cotton as soon as the crop is finished, with special reference 

 to producing a season on each estate of several weeks between 

 the destruction of the old crops and the planting for the new. 

 The portion of the report by the Assistant Superinten- 

 dent, comprising some eleven pages, records a very considerable 

 amount of work in connexion with pests and diseases. Much 

 of this is in direct continuation of that recorded in the 

 previous Annual Report of the Local Department (see Agri- 

 cultural News, Vol. XII, p. .58). 



With reference to plant inspection, it is stated that seven 

 species of scale insects, several species of aphis, and five 

 species of caterpillars not known to occur in Barbados have 

 been intercepted. 



Root borer {Biaprcpes ahlireviatus, L.). The continued 

 study of this pest of sugar-cane has led to increased knowl- 

 edge as to its life-history and habits, but nothing new since 

 the last report has resulted as to methods of control or 

 natural enemies. The collection of the beetles during the 

 year under review amounted on one estate to 69,700 from 

 June to NovemI)er; the greatest abundance was recorded in 

 late October and early November, the collections for the 

 week ended October 28 being 7,500, and for the week ended 

 November 4, 7,700. 



Although the period covered by the Annual Report 

 extended only to March 31, 1913, figures for the collection of 

 Diaprepes beetles are given to include the time to August 22, 

 1913. 



From early November to early April the beetles were so 

 scarce that no collecting was done. 



Following slight rains in April, however, they began to 

 make their appearance again, and the daily collecting was 

 resumed with fairly regular catches ranging from about 

 500 weekly at first, up to 925 in the week ended July 11. 

 There then came a fairly heavy rainfall (7-61 inches) between 

 the 13th and 18th, and the numbers increased enormously, 

 rising to a maximum of 28,357 for the week ended August 1, 

 falling to about 12,000 in the following week. 



The discovery in the previous year of the situation in 

 which the eggs were laid made it possible to collect these 

 during the period when the beetles were most prevalent. 

 The boys who capture the beetles collected 6,138 egg 

 batches. The number in a batch ranged from thirty to 200; 

 the average of 60 batches counted was ninety four. The egg 

 capacity of a female Diaprepes is about 250, and the egg- 

 laying period in captivity extends, over a period of from three 

 to seven days, the shorter period probably being more usual 

 in the field. 



The beetles are active at night, hiding during the day 

 in axils of the leaves of sugar-cane and corn and among the 

 leaves of pigeon peas and cassava. 



The eggs are found fastened between the wind-split tips 

 of cane leaves, rarely in the same situation on corn, and they 

 have not been found on other plants though extended search 

 has been made for them. 



The field toad or crapaud {Bujo agua) feeds upon the 

 beetles. When the eggs hatch, the grubs drop to the ground, 

 and it is believed that many are destroyed by the ants 

 which are often abundant in the cane fields. It is sug- 

 gested that it might be possible to take steps to increase the 

 abundance of predaceous ants in the cane fields, and even to 

 introduce additional species for the better control of the 

 root borer. 



An account is given of the feeding hal>its of the grubs, 

 from which it appears that when the newly hatched larvae 

 penetrate into the soil they begin feeding on the cane roots: 

 later, from December to February, they attack the under- 



