330 



THE AGRICULTURAL NEWS. 



October 15, 1910. 



INSECT NOTES. 



SOME PESTS OF CACAO IN JAMAICA. 



The following is extracted from aa article by 

 Professor R Newstead, M.Sc, A.L S., etc , which appears 

 in the July number of tha Journal of the Royal Horti- 

 cultural Society: — 



ANTS DESTROYING THK FLOWERS OF THE CACAO. So far 



as one could gather, the nio.st destructive insect pest to the 

 cacao in Jamaica is a small black ' fire ant', apparently 

 a Myrmicid of the genus Solenopsi.s. It has been impossilile 

 so far to get this insect identified in this country, but it is in 

 all probaViility known to tlie American entomologists. In its 

 nest-building habits it re.seralJes the terrestrial species of 

 Formica and other allied genera found in the British Isles 

 and in other parts of the world. The nests of the species in 

 question were, however, generally constructed so that they 

 ■«ere partly protected from the direct rays of the tropical 

 sun, lieing sometimes completely overshadowed bj' the cacao 

 trees. In the Chapelton district their nests were found 

 scattered all over the plantations, and the ants were found 

 foraging al)0ut the branches of a very large percentage of the 

 cacao trees. The nests were often placed close to the trees 

 on which the ants were found wandering al>out;Iiutin several 

 instances these structures were also found on the outskirts of 

 the plantation, without apparently any regard to the distance 

 the ants had to travel in order to reach their feeding grounds. 



Many of the trees were foiind swarming with these 

 insects, but it was some time before one could olitain any clue 

 to the object of their search. Eventually it was discovered 

 that they were attracted by the ' honey dew' secreted liy 

 small colonies of plant lice (Aphidae), which were feeding 

 upon the leaves of the cacao, generally speaking, at some 

 considerable distance from the main stem and liranches. 

 In order, apparently, to screen their movements, the ants 

 constructed for them.selves a narrow gallery or covered 

 way, leading from the ground up to a point where the 

 branches diverge from the main stem or trunk, or some- 

 times even to a greater elevation. The gallery was in 

 all cases formed of pellets of earth, of a very fragile nature 

 and easily removed. Having reached the main branches of 

 the cacao under cover the insect sought further protection Viy 

 forming larger covered ways among the dead tlowers which 

 had accumulated in the bifurcations of the branches and also 

 among the clusters or ' cushions ' of tlowers upon the main 

 branches. In the latter case the pedicels of the flowers had 

 apparently l>een injured in such a way as to ])revent them 

 from falling from the tree, so that they remained in situ, 

 shrivelled and dry, for indefinite periods, forming excellent 

 retreats for the ants. 



From these shelters, they seemed to l>e constantly mov- 

 ing to and fro among the upper branches of the cacao, seek- 

 ing for the sweet juice secreted by the aphides. The dead 

 flower-clusters were easily removed and, although carefully 

 examined, did not appear to be cemented together liy soil or 

 other substances. At first, one suspected that the flowers 

 had died from some unknown disease, but after careful investig- 

 ation one came to the same conclusion as the planter, that 

 they were destroyed liy the ants. This was confirmed liy the 

 fact that the dead 'cushions' always occurred upon the 

 lower portions of the main branches, and that they were 

 invariably tenanted by these insects. The loss occasioned in 

 this way was often considerable, and several methods of check- 

 ing their ravages had been attempted with, unfortunately, 

 l)ut little success. 



A mixture of lime, kerosene, turpentine, etc., had been 

 tried as a preventive, but had proved a failure. Gas lime 

 applied to the earth near the tree was effectual for a time, 

 but on losing its offensive odour became useless. The system 

 of grease-banding, in use in the country and elsewhere, was 

 recommended for the pest, and as l)Oth tar and grease were 

 availal)le it was suggested that this might be used as a sub- 

 stitute for the proprietary article manufactured for such pur- 

 po.ses. The result has not yet been communicated to me, 

 and I am still in doubt as to whether such a com- 

 pound will retain its viscosity for a sufliciently long 

 period in the tropics, and thus act as a barrier to 

 the inroads of the ants. This preparation should be 

 applied to a strip of grease-proof paper to prevent direct 

 contact with the bark of the tree. 



LARVA K OF A WOOD-BORIXG BEETLE IN,IURING THE CACAO 



TREE. 'I'he larva of a longicorn Iteetle was tunneling the bark 

 and wood of cacao trees in the Chapelton district. Its 

 occurrence was extremely local, and so far as one could gather 

 was fortunately, not of a serious nature. All the examples 

 discovered had confined their attacks to the lower portions of 

 the stem or main liranches and always tenanted a spot which 

 .showed evident signs of either previous injury or decay. The 

 subject requires further investigation, though it is doubtful 

 whether the insect can, for the present at least, be looked upon 

 as a serious pest. 



As a means of prevention, tar .should be aiiplied to the 

 ends of all freshly cut branches or other wounds produced by 

 pruning or by other means, as a precautionary measure against 

 the attacks of this insect. 



CHRDLER-WEEVIL OF THE 0E4NGE AND CACAO (PrepodeS 



jutiutus). A pest of a much more serious nature than the 

 larva of the longicorn beetle already referred to, is a brilliant- 

 ly coloured weevil belonging to the Eynchophorus section of 

 the Coleoptera. The larva of this handsome insect is a very 

 serious pest to both the orange and cacao, and its methods of 

 attack are very striking and distinctly characteristic. The 

 grubs occur, invariably, just below the surface of the ground, 

 and at a point usually immediately above the junction of the 

 roots with the main stem of the tree; and they eat away every 

 portion of the bark, right through the cambium layer, often 

 completely girdling the stem. Every trace of the bark may 

 l)e removed for a distance of 2 inches, .so that a complete 

 broad ring or girdle is formed, resulting in the ultimate death 

 of the tree. Cacao trees thus attacked sometimes throw out 

 adventitious roots just above the girdle, and in such cases the 

 tree may survive for a time, but it rarely, I believe, recovers. 



The complete life-cycle of this pest has not yet l)een 

 fully traced out, but Mr. E. J. Wortley has been successful 

 in rearing the beetles from larvae taken from the roots of 

 orange trees. The grub or larva is footless, and whitish in 

 colour, measuring approximately 1 inch in length when fully 

 matured. The adults are very handsome insects and are 

 closely related to the so-called 'diamond beetles'. 



At the i)resent moment, one can say very little regarding 

 the geographical distribution of this pest outside the island' 

 of Jamaica. There is, .so far as one can find, no record of its 

 occurrence as a pest in the Lesser Antilles, though several' 

 allied snout- beetles occur in Barliados — the weevil-borers of 

 the sugarcane (Sphenophorus ser/ceMs and Diapirejies ahhrevi- 

 atus) and the grain or granary weevil (Calandra oryzae). 

 In Dominica and Montserrat is the destructive palm weevil 

 {Rhyncophorus palmarum); and in Trinidad the banana is 

 attacked l)y Spenophonts soi-didns. 



As to the distribution of the girdler-beetle in Jamaica 

 one has very little information to rely upon, but it evidently 



