234 



THE AGEICUETV'EAL NEWS. 



July 18, 19U. 



INSECT NOTES. 



INSECT PESTS OF SUGAR-CANE IN 



BRITISH GUIANA. 



In the previ(in> numlier of tla- Aiiricultural Nevs, tlie 

 report of the Govenmient Bioh.igist on Insect Pests in British 

 Guiana was reviewed. In the pre.sent issue, it is proposed to 

 devote the Insect Notes page to a review of a report Ly 

 Mr. H. W. B. !Moore, Entomologist for certain groups of 

 estates in British Guiana. The report, which covers the yeai- 

 191.3, was issued in May 1914. Mr. Moore's report for 1912 

 was reviewed in the Ai/riculturai News for August 16 and 

 30, 1913 (Volume XII, pp. 266 and 282). 



Mr. ]kloore's report is of interest because it is an account 

 of practical field work in applied entomology in which useful 

 records are presented, and also because it is the only report of 

 its kind issued in tlie British Colonies in tropical America, 

 j\lr. ;Moore being employed by the proprietors of certain 

 groups of estates, while other workers in similar lines of work 

 are Government officials. The report deals almost entirely 

 with the insect pests of sugar-cane, those of rubber, the only 

 other crop discussed, being few and of little importance. 

 SMALL MOTH BORERS (Di'itroea S'icrharalis and £>. canella). 



Of the insects which attack sugar-cane m British Guiana, 

 these are given the place of first importance. 



The work of cutting out dead hearts and collecting 

 caterpillars of the .small moth borers was carried on during 

 the year. The number of caterpillars recorded as captured on 

 .seventeen estates amounted to 2.o, -583,987, an increase of 

 more than 6-5 per cent, over the captures of the previous year. 

 It is stated, however, that this increase is the result of more 

 work and better work rather than of any marked increase in 

 the degree of infestation by these in.sects. 



The collecting of fresh egg clusters was continued 

 during the year. The records given, show that 180,000 were 

 collected on the twelve estates where records were kept, 

 the largest number for one plantation lieing 64,442 at 

 Plantation Enmore. The writer of the report states that 

 these figiu-es are not altogether reliable, since in certain 

 instances eggs of other insects were included, and at one 

 estate he observed a consideraljle collection of eggs that had 

 already hatched. This appeared to be the work of a gang of 

 inexperienced collectors. 



The egg clusters that have hatched are white or pearly 

 white in appearance and resemble minute fish scales or tiny 

 bits of cast snake skin. These are of no importance and 

 should not be collected. Egg clusters in which the eggs have 

 turned l)laek should be left in the field, since the black 

 appearance is due to the presence of parasites in the eggs. 

 The parasites emerge from these and attack fresh eggs, thus 

 aiding in keeping down the nund)ers of the moth borer. 



The egg clusters which have ni>t hatched and which are 

 not parasitized are the ones which should be collected. They 

 are yellow-white, reddish or orange-cf)loured. Such egg 

 clusters should Ije allowed to hatch after lieing collected, under 

 such conditions that the caterpillars which come from them 

 cannot find their way to growing canes. In the meantime 

 any parasites which may be in the eggs will have an oppor- 

 tunity to complete their development and escape, when they 

 will return to the cane field and attack other egg clusters. It 

 is strongly recommended that all estates should regularly and 

 persistently collect egg clusters, beginning as soon as the canes 

 commence to shoot, thus .saving a large proportion of the 

 cutting out of dead hearts by causing the removal and des- 

 truction of many tliousands of (•ater])illars before they damage 

 the cane at all. 



The use of trap lights for the capture of the moths in 

 addition to the cutting out of dead hearts and the ctjllection 

 (jf the caterpillars that are in them is also recommended as 

 a useful method of control, in spite of the fact that many of 

 the insects caught are not moth borers: others are males, and 

 many of the females may have already laid all or .i part of 

 their eggs. 



In this report, stress is laid on the importance of the 

 projjer care of refuse cane-tops which, if left in the fields, are 

 a source of a prolific infestation for the next crop. 



Burial of such material is recommended as the best 

 ccmrse to pursue for the destruction of the insects contained 

 in it, when this is possible from the condition of the soil and 

 the supply of labour. Where doing so is impossilile, tops 

 might be burned or soaked a few days in punts in the canals. 



The parasites of the moth borer mentioned are a new 

 species of egg parasites: Aphinurus alecto; two parasites of 

 the larvae, Iphiaulaxmediinus and Cremnops parvifasciatus. 

 In addition, Dipterous parasites (Hies of the family Dexiidae) 

 have been bred from moth liorer pupae found in the tunnels in 

 the cane. 



Several predatory insects have been observed, such as 

 black ants devouring fresh egg clusters, the larvae of a click- 

 beetle (Coleoptera. family, Elateridae), and the larva of a fly 

 (Difjtera, family, Strationiyidae), and the parasitic fungus, 

 C'ordi/ceps harheri, has been found on larvae which appar- 

 ently had been killed I>y it. Xone of these are considered 

 to exert any appreciable ett'ect on the numbers of the moth 

 borer, however, although they are of interest. 



In estimating the amount of the damage caused by the 

 ravages of the small moth borers, Mr. Moore calculates that 

 to collect the 2.5i nullion caterpillars it was necessary to cut 

 out at least 100 million dead hearts. In addition to the 

 injured stalks cut out as dead hearts, there are greater 

 nundiers still, in which the injury is not se\ere enough to 

 prevent their being sent to the mill. In these the injury 

 is shown by a partial loss of juice, and by a defective quality 

 of the juice expressed from them. 



In Porto Rico, it has been estimated that the loss in 

 sugar in the canes that go to the mill amounts to about J-tou 

 of sugar per acre, as a result of the loss of juice, the 

 increase in the proportion of fibre and the deterioration in 

 the quality of the juice obtained. It is stated that the 

 damage to sugar-cane is greater in British Guiana than in 

 Porto Rico, but if calculated at the same rate it would amount 

 to about 20,000 tons of .sugar per annum in British Guiana, 

 on the canes that go to the mill, to say nothing of the loss 

 that is represented by the millions of dead hearts cut out, and 

 the much greater number of canes that are killed in 

 the field. 



TERMITES OR WOOD AXTS. 



Next to the small moth Ijorers, termites are considered 

 the most damaging insects in the sugar-cane fields of British 

 Guiana. The nests of these insects, principally of two species, 

 Eulcrmes costaricensis and Mirotermes nv/rittis, were 

 destroyed on eight plantations to the number of 460.000. 

 These nests were collected and destroyed wherever and when- 

 ever found, and it is stated that this method persistently 

 carried out results in markedly imjiroved conditions as i-egards 

 the degree of infestation. 



THE GIANT MOTH BORER {CuSt)lia Ucus). 



Taken on the whole, the attacks of Castnia liais were 

 not strikingly less in 1913 than in the preceding year. 



The collections on seventeen estates during the year gave 

 a total of nearly 600,000 moths and 1,370,000 caterpillars, 

 a total of over l",970,000 of both stages. In the previous year 

 the collections amounted to about 346,^00 moths, 761,500 



