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THE AGl'.lCULTUKAL NEWS. 



M.UKH 15, 1913, 



INSECT NOTES. 



THE LIME TWIG BORER. 



Towards the end of 1','12, limes in a certain district in 

 Antifua were found to be suffering from an attack of a new 

 pt-st. The attack was evident from a large number of 

 branches which had broken down and were hanging in the 

 trees in a dry and withered condition, whilst a few of these 

 branches were found to have been broken off' conipletelj* and 

 were lying on the ground. Examination revealed the fact 

 that at the point of breaking each of these branches had been 

 neatly cut nearly all round, so that, as the wood dried, a slight 

 gust of wind would have caused it to break at the point. 

 A search for the insect which was responsible for this damage 

 showed that there was no tunnel or injury extending from this 

 breaking p.int on the portion of the branch toward the tree 

 itself: but in every instance the portion which had broken 

 down or fullen off' was found to be more or less tunnelled, and 

 in many instances a borer beetle larTa was discovered in the 

 tunnels. Specimens of the adult, which is a small longicorn 

 beetle, , have been reared from the larvae, and they have now 

 been identified through the courtesy of Mr. Guy A. K. 

 Marshall. Scientific Secretary to the Imperial Bureau of 

 Entomology, who states that the technical name of this 

 insect is Elaphklvm mite. Xewman, and that there are 

 specimen.s of it in the British Museum from St. Thomas. 

 .St. Bartholomew, St. Kitts and Guadeloupe. 



This insect wa.s found to occur in two localities in 

 Antigua at nearly opposite sides of the island At that time 

 it was supposed to be a local pest. From the information 

 now at hand, however, it appears to be of fairly general 

 distribution throughout the Leeward Islands. 



The following information is taken from a report on 

 a visit to Antigua in December 1912, by Mr. H. A Ballou, 

 M.Sc, Entomologist on the Staff of the Imperial bepartment 

 ff Agriculture. 



'The attack on a lime branch ai'parently always begins in 

 a small twig; that is lo say, the egg is laid on a small twig 

 ;ind the young grub first begins feeding in this situation. It 

 is not possible to say whether the twig on or in which the egg 

 is laid i.s dead or dying at the time of egg laying; but in 

 every instance of attack observed, both in the field and in 

 specimens forwarded to this office, the small twig has been 

 found entirely eaten out, the dead interior connecting with 

 the tunnel in the larger branch from which the twig springs. 

 The larger branch is always more or less girdled by the tunnel 

 ( f the grub. This girdling seems to be the first thing done 

 by the grub on reaching the larger branch, and it results 

 in the death of the branch beyond the point of the girdle. 

 The borer tunnel does not circle the twig in such a manner as 

 v< cut it off completely, but the direction is rather .--pi ral so 

 that, as the injury to the branch becomes more and more felt, 

 the limb breaks down and is usually left hanging for some time. 

 The entire grub and pupa stages of development are passed 

 vv ithin this branch, the adult beetle only issuing from the 

 deid branch some time after emerging from its pupal con- 

 dition. This last statement is based on the fact that the 

 adult beetles fully formed, and with mature colours, 

 liave been found in this situation, apparently never having 

 hoen out. 



The length of the life-cycle is not known. The number 

 of eg gs laid by a single female, and the other food plants on 

 which they are kid have also still to be learned. The 

 life cycle, may safely be said to be comparatively long, since 

 .specimens have been found, both larval and adult, in lime 

 J wigs which had apparently been dead for a long time, and 



aa it seems likely from what we know that this insect begins 

 its feeding in living wood, this would indicate a lon»: 

 life-cycle. 



'In another locality, the same insect was found at work, 

 in II few neglected lime trees, and a grub was found in 

 a tamarind branch which appe.ired, from the nature of the 

 tunnel made, tube the same as the one in the lime trees. 

 -V piece of dead AcaCia wood found at this same place had 

 been bored and girdled in a manner very similar to the limes 

 and it mav be that the Acacia is also a food plant of this 

 insect, Xo indiiations of the presence of the insect were 

 found in the other parts of the island visited. 



'It is likely that the beetle has occurred as a pest of 

 limes in Antigua for some time but has been overlooked. It 

 is very probable that it has a considerable range of food plants 

 from which renewed attacks on limes may be experienced 

 from time to time. The presence of this in.sect, however, 

 should not prevent the development of the lime industry ir» 

 Antigua, as it ought to be a fairly easy pest to control. 

 Within a very short time from the beginning of the attack, 

 the grub injures the branch, in which it is to complete its 

 development, to such an extent as to make the damage very- 

 conspicuous. First of all the leaves wilt, they then discolour 

 and dry up; about this time the branch breaks at the point 

 of girdling, and usually hangs in the tree, forming a very- 

 conspicuous notice of the presence of the beetle. 



'The remedy to be employed is therefore obvious. Any 

 dying branch on which the leaves are curling up or turning- 

 yellow, should be carefully examined for the presence of the 

 borer, and if the grub can be found it may easily be dug out, 

 or the branch may be removed sufficiently far back toward 

 the tree to ensure the removal of the grub. It is more- 

 likely that the attacked branches will most often be detected 

 after the breaking down has occurred, and then the point at 

 which the branch should be cut is clearly indicated. When, 

 the branch has broken, the grub will always be found in that 

 part of the branch beyond (or outside of) the break. If all 

 these broken branches in which the grubs occur can be 

 collected and burned, say at intervals of one month, it 

 ought to be possible to reduce the numbers of this insect to 

 such an extent that it would no longer be a pest. 



'The loss of the attacked branches, in the first instance,., 

 is, of course, an important item from the lime grower's point 

 of view; but if this .system of collecting is carefully carried 

 out there will probably be very little infested material to 

 collect after the first two or three tiuies, becau.se the destruc- 

 tion of all the developing grubs over a period of three ot^ 

 four months will very largely preclude further increa.se and 

 development on the part of this insect,' 



It may be useful to compare briefly the habit.s of the 

 lime twig borer with those of other booties of the longicorn 

 group which cause the breakini; off of twigs and branches 

 (the oak pruner and the twig ginllers), or which by reason of 

 their attacks on limes (the bark borer) are of interest ir> 

 this connexion. 



In the case of the lime twig borer it seems to be natural 

 for the larva to tunnel around the branch in such a manner 

 as to cause it to break down but not U> be severed. The 

 dead wood in which the larva continues to live beinc thus 

 kept off the ground, the decay of the woody tissue is less 

 rapid than would be^*>ie case if it fell and came under the 

 influence of the moisture of the ground in the shade of the 

 growing trees. In other words, the larva lives on dead and 

 dry, but not decaying, wood. 



Elaj'lnidioii 'UloMnu, which occurs commonly in the 

 United States, is called the oak pruner because it often 

 attacks the twigs and branches of oak: it also attacks the 



