THE AGRICULTURAL NEWS. 



July 12. 1919 



INSECT NOTES. 



SUGAR-CANE AND HARDBACK GRUBS 



IN ANTIGUA. 



The Entomologist of the Imperial Department 

 of Agriculture paid a visit to the Northern Islands in 

 March of this year, to inve-stigate certain insect pests 

 of crups in those islands. The following is reproduced 

 from his report to the Imperial Commissioner of 

 Agriculture, on his return to Barbados: — 



The hardback grub still continues a serious pest of 

 «ugar-cane and other crops in Antigua. 



The grubs are to be found most actively feeding from 

 July or August, to January and February. About March or 

 April they s'op feeding, change to pupae, and then to 

 adult beetles, wLicL issue forth with the early rains in 

 April or May. Moat of the beetles come out of the ground 

 at about the same time, and egg laying appears to take 

 place within a short time of emergence, and not to extend 

 over a very long period. 



Planters know from experience that from August on to 

 March or April, in those sections of the island where the 

 grabs have occurred, sugar-cane cuttings newly planted, 

 corn, onions, sweet potatoes, and yams are liable to suflFer 

 from attack. 



During my visit in the only locality where the 

 insects were abundant, I found more than half of those dug up 

 were in the pupa and the beetle stages. The beetles found 

 were still in the pupal cell. This is a closed cavity in the soil, 

 which the full-grown larva has prepared, and where the 

 change fiom larva to pupa, and from pupa to beetle takes 

 place. Some of the insects transform near the surface, and 

 others go deep into the soil. 



The hardback grubs appear to attack field after field, 

 and not to remain year after year in the same fifld. Plant 

 canes appear to be less attacked than ratoons. 



The beetles on emerging from the soil with the first 

 good rains in April or May, appear to be attracted to 

 trees or bushy plants whore feeding and mating take place 

 at night. During the day they hide, probably in the ground. 

 The eggs are laid in the ground near the places where 

 the adults have congregated. If the beetles have emerged 

 from the soil of a field where the canes have just been 

 cut, they will probably tty away to trees or to standing 

 eanes, while if they emerge from the soil of a field where 

 canes are still standing, it i.i likely that they may reinfest 

 the same field. 



If the history of a certain number of fields could be 

 obtained, giving the dates of planting and reaping of all the 

 crop (<rown over a period of years, and the .seasons in which 

 grub attacks have been noted, with information as to the 

 •everity of the attacks, much light might b« thrown on these 

 points, and the lines of future observations might I e indicated. 



At any rate, this habit vl fiiglit would ."eem to explain 

 why the attack is experienced in dilVeient field.s in different 

 seasons; and the supposition in regard to beetlts coming out 

 of the soil in fields where the cane? are still standing, would 

 explain why certain fields from which canes have been reaped 

 are so badly infested as to make it impossible to grow satis- 

 factory crops of corn or onions, and difficult to establish the 

 next crop of canes. 



Hand collecting of the grubs appears to offer a means 

 of greatly reducing the number.s of grubs in the soil, and 

 this collection is much helped by the use of a trap crop 

 which attracts them to its roots. Indian corn is a most 

 useful plant for this purpose. Its roots are all neir the 

 surface of the soil, and the grubs are thus attacted to the 

 upper layer where they can easily be collected. It is a 

 quick growing, vigorous plant which quickly shows root 

 injury, and being a surface-rooted plant, it is easi y pulled 

 out. 



In Mauritius the Phytalus beetle is captured on traps 

 consisting of leafy branches of bush or trees stuck in the 

 soil from which the beetles are emerging. The beetles 

 climb upon these branches at night, and they are searched 

 for with lights. Enormous numbers are captured in this 

 way. Phytalus smith! is also collected in Barbados in 

 very large numbers. They are found on canes, pigeon 

 peas, and other plants. It corn could be planted in an 

 infested field as soon &» the canes were off, and early 

 enough for the corn to be well-estiblished by the middle 

 of April, many beetles might be attracted and collected at 

 night. 



If the foregoing observations on the life-history of the 

 beetle prove to be correct, it would appear that as far as grub 

 control is concerned, it would be good practice to allow the 

 cane on badly giub-infested fields to stand until after the 

 emergence of the beetles, in order that they may deposit their 

 eggs on the canes in the same field. As soon as the canes 

 are cut, the land should be worked and p'anled with corn; 

 when this is attacked it should be pulled, and as miny of 

 the grubs as possible collected from the soil, and corn 

 planted again. If many grubs have been left in the soil 

 at the first collecting, the second crop of corn will be attacked, 

 and the pulling and collecting .should be repeated. Practical 

 financial considerations, however, may dictate the early har- 

 vesting and milling of badly attacked canes, in order to avoid 

 the loss in weight and quality which ensues when unhealthy 

 canes are allowed to remain standing for any length of time 

 after becoming ripe. 



While the use of the trap crops of corn seems to be 

 fairly well understood, it may te well to emphasize points 

 in connexion with it. One point is this: that when corn is 

 planted in infested fields for the purpose of trapping grubs, it 

 should be considered that the corn is planted entirely for the 

 purpose of grub control, and that no yield of grain should 

 be expected from it. Another point is, that when the attacks 

 of the grub on the corn become fairly noticeable, not only 

 the attacked plants, but all the corn should be pulled, and 

 the grubs carefully collected. 



Poultry and pigs, and certain wild birds feed upon the 

 hardback grubs, but the.se do not aeem to bo present in 

 sufficient numbers in Antigua fields to exert much influence 

 on the prevalence of the pest. In certain sections of Antigua 

 the blue gaulding is abundant, and worthy of mention in 

 this connexion. This bird is a valuable insect eater, and it is 

 well that it is protected in the island. It i.s often to be .seen 

 in cano fields, and there can bo no doubt that it eats the 

 hardback grub, and probably finds and eats the beetles also. 



The parasites which attack thi.s kind of insect in other 

 localities .seem to be of little value in Antigua, so far as has 



