58 



THE AGRICULTURAL NEWS. 



February 19, 1910. 



INSECT NOTES. 



THE ROOT BORER OF SUGAR-CANE. 



(Diaprepes abbreviatns.) 



AVithin the past three or four months, the appearance of 

 the sugar-cane plants in certain parts of Barbados has indi- 

 cated the presence of the root borer, and when these affected 

 canes have been dug up, the root borer grubs have been found 

 at work in the underground jiortions of the plants. 



LiFF.-HisTORY. The Kcv. \. B. Wat.son, F. E S., worked out the 

 life-history of this insect and published, in the Wi/st Indian 

 Bulletin (see Vol. IV, p. 37), a very interesting and instruct- 

 ive paper entitled 'The Root Borer of the Sugar-cane'. In 

 this paper, which was issued early in 1903, it was stated that 

 the length of time occupied in the life-cycle of the root borer 

 is about 3.57 days, divided as follows: egg 10 days, larva 

 312 days, pupa 1-5 days, imago '20 days. During the last 

 20 days, the mating and egg-laying occur. It is also 

 stated that the principal food plants of the^root borer 



roots and leaves is cut off, and the phmts die for want of 

 water, as this cannot be transmitted to the above-ground 

 portions of the plant, even though the roots are able to col- 

 lect it. The appearance of canes dying from the attack of the 

 root borer is very much like that of canes dying from root 

 fungus (J/'irasmitis) or from drought. 



HISTORY OF PRESENT ATTACK. The present attack was 

 first notice<I in' Barbados during December last, in full-grown 

 canes, then ripening. A few stools at the edges of the fields 

 were seen to be in a dying condition, and the!:, as the attacked 

 canes gradually succumbed, the number of dying stools was 

 seen to be greSfly increa.sed; finally, at the beginning of the 

 present month, a field of plant canes, in which the young 

 shoots were about one foot in height, was discovered to be 

 infested, and iiiany of the young sprouts were dying. In the 

 case of the young plant canes, it was found that the cuttings 

 which had been planted, and from which the shoots were 

 springing, were tunnelled througli and through, all the stored 

 up food for the shoots having been consumed. As many as 

 four grubs ha^'fe been found in one cane cutting. 



REMKiHEst. In dealing with fields of young canes badly 

 attacked by root borer, the most iirofitable course will prob- 



larvae are sugar-cane, sweet potato, iraphee, ground nut, an4' , ably be to fork or plough up the canes, and destroy in this 



Guinea corn. Root borer larvae have also been found in 

 the main root of bread-and-cheese (Pithecolohium Uiu/vi-i-cati) 

 and among the roots of young palms. The plants which the 

 root borer does not attack much, if at all, are ochro, cassava, 

 yams, eddos, woolly pyrol, pigeon pea, bonavist, rouncival, and 

 beans generally. 



Since the publication of this jiaper, cotton 

 has come to be the most important of all the 

 minor crops on many estates, some of which 

 are in the districts where root borer is most 

 abundant, and .since no report has come to 

 hand of damage to that plant by this insect, it 

 would seem that 'cotton might be added to 

 the list of plants not seriously attacked. 



SIMILAR PESTS. There are three species 

 of beetles, whose larvae are often confused, 

 which are found in or about canes. Two 

 of these are weevils. Sp/ienophorus acriceus (Fig. 6) is the weevil 

 borer, which in its larval stage attacks canes above-ground and 

 tunnels in them, always 

 above-ground. Diaprepes 

 abhreviatug (Fig. 7) is the 

 root borer which, in the 

 larval stage, tunnels the 

 underground portion of the 

 cane and eats the root.s. 

 The third of these insects 

 is the hard-back {Lifjyrus 

 tumulosus, Fig. 8), which 

 lives in the ground and 

 nearly always feeds on dead 

 or decaying vegetable mat- 

 ter. This grub has three pairs of slender legs, and is thus 

 distinguished from both the others, which have no legs. 

 As has been already stated, one of these always attacks 

 the cane above ground, and the other under the ground; 

 they may be further distinguished by the ]5resence, in the 

 weevil borer, of a large hump, or abdominal distention. The 

 accompanying illustrations will make these differences clear. 



NATURE OF DAM.\GE. The damage to the cane by the 

 root borer results from the destruction of a very large 

 portion, sometimes practically all, of its underground stem 

 system. The injury to the fibrous roots is not so complete 

 and not seen as plainly. The effect of the demolition of 

 this underground stem system is that the connexion between 



Fii;. G. Weevil Borer. 



7. Root Boreh. 



way as many of the grubs as possible. Carbon disulphide 

 may be found useful in dealing with attacks of root borer in 

 young canes if the attack is not very serious, and if it can be 

 taken at its earliest appearance. Experiments are necessary 

 in order to demonstrate the usefulness of this material, and 

 the expense of its application in field work. 



i'revention. The most .satisfactory 

 method of dealing with root borer will be 

 one that includes estate practice calculated to 

 reduce its numbers. 



The full-grown canes which are at 

 the present time being attacked are now 

 ripening, and will be cut and milled within 

 the next two or three months. Planters 

 should make every effort to have all cane 

 stumps in infested fields dug out at the 

 earliest possible moment after the canes have 

 been removed. If a supply of labourers is available, the stump.s 

 should be headed out and thrown into stacks, with plenty of 

 lime. If it is not possible to have the stumps removed 

 from the field, they should be dug up and chopped open 



with two or three cuts 

 of the hoe, and left on 

 the ground. In any event, 

 the bottom of the holes 

 should be forked and limed, 

 so as to thoroughly dry out 

 an_y grubs or pupae that 

 may be left behind when 

 the stumps are dug out. 

 The breaking up of the 

 stumps will expose the 

 birds, lizards and 

 of the borers in 

 and in the holes 

 ever 

 canes 

 ones. 



Fig. 8. Grur of the Harh-raik. 



grubs to drying and to the attacks of ants, 



toads; it seems likely that very few 



the cane stumps dug out in this way, 



forked and limed as has been recommended, will 



arrive at maturity. It will be found that attacked 



are very easy to dig, in comparison with healthy 



This is not .^an expensive practice, and ought to become 



a part of the routine work on every estate. 



On estates where ratooning is practised, the stumps 

 should be dug as soon as the ratoon crop has been taken off. 

 If fields which were intended for ratooning are badly, 

 attacked, it will probably be found most profitable to dig 

 the stump.s, as suggested above, and to omit ratooning 



