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THE AGRICULTURAL NEWS. 



August 25, 1917, 



INSECT NOTES. 



INSECT 



PESTS IN BRITISH GUIANA 

 IN 1916. 



The following notes are taken from the general report 

 by Mr. H. W. B. Moore, Entomologist for a group of estates 

 in British Guiana, on the insect pests occurring on these 

 estates during 1916. Previous reports have been reviewed 

 in the A(jri(u.Uural News from time to lime, and the last one 

 was referred to in the numbers for December 16 and 30, 1916 

 (Vol. XV, Nos. 382 and 383). 



A NEW SM,\LL MOTH BOREK OF SU(;AR-c;ANE. 



The present report contains among other features of 

 interest an account of a small moth borer wliich was discovered 

 by Mr. Moore in 1916. This insect had not been determined 

 up to the time of the publication of the report, so that it 

 may or may not be new to science. The caterpillar was 

 found to have a wide distribution, which probably means 

 that it has been a cane feeder for some time. It is new in 

 the sense of having been only recently discovered. 



This in.sect belongs to the same family, Pyralidae, as the 

 two species of Diatraea moth borers occurring in British 

 Guiana, but to a diftcrent sub-family. The Diatraeas come 

 under the sub-family Crauibinae, while the new borer belo-jgs 

 to the sub-family Phycitinae, which contains moths whose 

 caterpillars have a variety of habits, some being borers in 

 pods and the young shoots of certain plants, while others 

 are predaceous on scale insects, and others again attack 

 groceries. 



As stated above, this pest is widely distributed, but it 

 does not seem to be a persistent pest like the Diatraeas. 

 Mr. Moore suggests that it probably has more or less definite 

 times for appearing, but would be capable of doing consid- 

 erable damage if it ever became really abundant. 



Mr. Moore goes on to say that 'it attacks the shoot Iti 

 a slightly different manner to the other small borers. It bores, 

 as a rule, straight to the growing point, or the heart, and then 

 merely eats out a small cavity instead of making a longitudinal 

 tunnel. Its boring, nevertheles.?, has souie resemblance to 

 an incipient attack by D. mccharalis. The ebtrance hole 

 is circular, and very small, and there generally proceeds from 

 it a tube or gallery composed of earth and vi'getable matter 

 held together by web, thereby differing again from either of 

 the other borers. This tube frequently becomes detached 

 on cutting out the dead shoot, and then, the boring would 

 certainly be mistaken for that of D. saccharalis by anyone 

 not suspecting the existence of a third and very distinct 



borer The caterpillars are very readily alarmed, 



and are wonderfully frisky, thumping about like fishes out 

 of water. This trait constitutes a further difference between 

 them and those of the other borers. There is another differ- 

 ence also in the readiness with which they leave their 

 boring's, when the shoots are cut out.' 



The caterpillar is smaller than those of the other two 

 small moth borers, and is green in colour with nine reddi-sh 

 longitudinal lines extending from the middle of the third 

 segment to the em I of the body. The first .segment has 

 a lateral brown spot and a dark-brown dor.sal plate divided 

 in the middle by a green line. 



Mr Moore has found that the caterpillars do not 

 pupate within the boring, but outside, in a slight whitish 

 tocoon. 



The adult moths differ in colour according to the sex, 

 the forewings of the male being grey with a large dull yellow 



area. The forewings of the female are either grey with 

 very little yellow, or are a plain dark grey. The hind wings 

 of both sexes are a clean white with a slight brown border. 



THE SMALL Mo 111 BORERS {Diatraea sarcharalis and 

 D. canelta). 



These pests are still doing terrible damage and will 

 continue to do so, Mr. Moore considers, unless more control 

 work is done in the early stages of the sugarcane. In 

 connexion with the collection of egg-clusters, one of the 

 suggestions made by Mr. Quelch, (a former entomologist for 

 the above estates) was that the black, that is. parasitized 

 egg clusters should be taken from canes about to be cut, and 

 .should be distributed in ynung fields. Up to the present 

 time this method has been carried out regularly on only 

 two estates, but it is especially needed on estates where the 

 fieMs are burnt off prior to cutting, as it would save large 

 numbers of parasites ior distribution in fields where they 

 would do most good. 



The collection of the egg-clusters of the small moth borer 

 and the protection of the parasitized masses has often been 

 referred to in the pages of the Agricultural News. A con- 

 venient way of carrying out the mea.sures of control was 

 described in the number for August 30, 1913 (Vol. .\II, No. 

 296). A reference to this article, whicli was ba.sed on 

 Mr. Moore's 1912 report, will show that by this method the 

 escape of any hatching caterpillars can be prevented, and 

 at the same time the emerging parasites are allowed to escape 

 and continue their good work in the cane fields. Thi.'i 

 method could be tried with advantage in those islands where 

 the small molb borer is troublesome, and the simple apparatus 

 described in the above refeience could be set up in fields of 

 young canes where the parasites are needed. 



THE LAKliK MOTH BORER (CaStllia /iciis), 



.Mr. Moore found that the control work against the 

 large moth borer was of an uneven nature, being very 

 satisfactory on some estates, and rather the reverse on others; 

 and an increa.se of infestation is to be expected on those 

 estates where the collection of caterpillars and moths has been 

 neglected. 



iHE SMALL BLACK HARD BACK {Dyscinetus hidentatus). 



A fairly severe attack of this pest occurred on two 

 estates between April and .\ugust, and less serious outbreaks 

 were felt on other estates. The estates in question were 

 prepared for the outbreak, having suffered in the two previous 

 years, and a systematic collection ol the beetles helped to 

 reduce the damage. A fair number of eggs was collected on 

 one estate. These are laid .singly and loosely in the earth 

 about the cane stools, and the grubs feed on decaying 

 vegetable matter in the soil. It is the adult beetles that do 

 all the damage by destroying the young cane shoots and often 

 boring into the base of the plant. A closely related species 

 Dt/scinetus liaihalus occurs in Antigua. St. Kitts, and 

 Barbuda. The ScoUid wasp, Tiphia parallela, was found to 

 be a parasite of D. hidentatus in British Guiana. 

 KRo( : HOPPER ( Tomaspis fiavilatera). 



Theie was a severe outbreak of this pest on one estate 

 where over four million adults and nymphs were collectecl 

 and destroyed during the sea.son. The adults were caught 

 at the rate of several thousand daily by sweeping the drains 

 in the worst infested fields with wide-mouthed nets. This 

 was done on the artvi<;e of Mr. C B. Williams, Kntomologist 

 in charge of Froghopper investigations in Trinidad, while on 

 a visit to British Guiana. The froghopper was al.so destroyed 

 in small numbers on a few other estates. After a careful and 

 prolonged siarch Mr. Moore was able to find the egg of this 



