Cocoa Pests Research Articles

Pests of Cocoa

Pests of Cocoa

Megaceresium horni (Heller), a New Longicorn Stem Borer of Cocoa in the British Solomon Islands

A new pest of cocoa in the British Solomon Islands, Megaceresium horni Heller (Cerambycidae), is described. The larvae cause severe damage to branches by tunnelling through the pith and sapwood, on...

Biology, immature stages and rearing of cocoa-capsids (Miridae: Heteroptera)

Some aspects of the biology of four West African capsid pests of Cocoa, Distantiella theobroma (Distant), Sahlbergella singularis Haglund, Bryocoropsis laticollis Schumacher and Helopeltis corbisieri Schmitz (Miridae: Heteroptera) are briefly summarized. Their immature stages are described and sketched in detail. Keys to distinguish all the larval stages are given and the techniques for rearing them reviewed. The systematics of Bryocorinae is discussed.

The end of the first cocoa shade and manurial experiment at the Cocoa Research Institute of Ghana

SummaryIn an Amelonado cocoa (Theobroma cacao L.) shade and manurial trial, no-shade trees yielded three times as much as shaded trees over 17 years of continuous cropping, but it is inferred that the economic life of an unshaded Amelonado cocoa farm in Ghana may not last for more than 10 years of intensive cropping. No-shade trees require more fertilizer than shaded ones, and lack of fertilizers, especially P, will cause a decline in yield in less than 10 years. A mean loss of over 50% of organic carbon within 15 years, with the apparent organic carbon decomposition constant (Kc) = 4.67, was used as a measure of deterioration of the soil productivity. Deterioration of cocoa was rapid under the no-shade conditions partly because of the high loss of exchangeable bases and the greater stress caused by the higher yield. Trees under stress tended to become more susceptible to insect pests and probably to diseases. Shade conditions alfected the distribution of the . insect pests of cocoa. The no-shade regime f...

Pests of cocoa by P. F. Entwistle

<i>Pests of cocoa</i> by P. F. Entwistle

Mirids and Other Insect Pests of Cocoa

Mirids and Other Insect Pests of Cocoa

Observations on the biology of some members of the genus Tragocephala (Coleoptera, Lamiidae) associated with Theobroma cacao in West Africa

Members of the genus Tragocephala are widespread as pests of cocoa, and other tree crops, in West and also in East Africa. Those known to be associated with cocoa in West Africa are listed and observations are given on the biology of two of the more important, T. castitnia theobromae Entw. in Ghana and T. castnia cacaoensis Entw. in Nigeria, and a method of laboratory rearing and breeding is described.The egg is laid in an unhardened stem and the oviposition behaviour is complex; the stem is first girdled at a point where it is less than one centimetre in diameter and an oviposition slit excavated above the girdle. The ovipositor is inserted into this slit and the egg is concealed inside the stem; the adult finally closes the oviposition slit with her mandibles.The egg hatches after 11 days and the young larva bores upwards in the dead wood above the girdle. This phase appears obligatory and is followed by one in which the larva bores down into the living stem below the girdle. The mean larval period of T. castnia theobromae in the laboratory was 143 days (range, 70–228 days).A pupal chamber is made by severing the stem beyond about 10 cm. above the end of the gallery and filling the aperture with shreds of wood. The pupal period, in the last half of which adult coloration begins to show, is about 20 days for T. castnia theobromae and 23 days for T. castnia cacaocnsis.Laboratory evidence suggests that there is a post-pupal resting phase in the pupal chamber followed by a free-living non-feeding period; in T. castnia cacaocnsis these lasted on average 6·5 and 4·2 days, respectively, and were followed by intensive feeding on green unhardened stems. The length of life of caged adults varied greatly but the mean was 57·0 and 55·5 days for males and females, respectively, of T. castnia theobromae and 32·0 and 28·5 days for T. castnia cacaoensis. The least preoviposition period noted for T. castnia theobromae was 20 days and previously unmated males and females of this subspecies were still fertile up to at least 76 and 162 days, respectively. Mating normally initiated the bark-ringing behaviour of females and the maximum number of eggs laid by a female of T. castnia theobromae was 146. Considering only individuals that laid 25 or more eggs, an oviposition rate (number of eggs laid per day between first and last oviposition) of 0·51 was recorded for this subspecies. Host plants alternative to cocoa are listed for T. castnia theobromae and T, castnia cacaoensis.The oviposition activity of T. castnia theobromae was least in June, July, August, December and January, whilst for T. castnia cacaoensis very few eggs were laid in the main dry season (November to the following February).The eggs of T. nobilis (F.), T. castnia theobromae and T. castnia cacaoensis, and of another species in the Congo Eepublic, are attacked by the Encyrtid Aprostocetus lamiicidus Kerrich, which in Nigeria appears to undergo a larval diapause in the dry season. Whilst only 5·5 per cent, of eggs were attacked in Ghana, over 50·0 per cent, were attacked in Nigeria. There was an average of 11·7 individuals per egg and the ratio of males to females was 1:2·7.The Tachinid Billaea vanemdeni Fennah was parasitic on larvae of T. nobilis and T. castnia theobromae in Ghana, where its larval stage was in the region of 197 days and its pupal stage 23 days. Incidence of attack was highest from April to July and the two main adult emergence periods were June and September/ October.An Ichneumonid, Nadia sp., is parasitic on either larvae or pupae of T. castnia cacaoensis in Nigeria. Scolytid species incursive in wood dying after being girdled destroy many eggs in Nigeria, where geckoes and ants are thought to be responsible for loss of larvae.Tragocephala can be a locally important pest, especially of seedling cocoa and its numbers may increase considerably if unsuitable chemical control methods are used against other pests of cocoa.The bark-ringing habit in Cerambycidae is discussed.

New Pests of Cocoa (Theobroma cacao L.) in Ghana following Applications of Insecticides

VARIOUS chlorinated hydrocarbon insecticides have been tested in large field trials in Ghana in recent years against the cocoa capsids Sahlbergella singularis Hagl. and Distantiella theobroma (Dist.). Great success has led to the widespread use of γ-BHC in routine control. One of the most persistent of these insecticides, ‘Dieldrin’, has also been used experimentally with great promise for controlling the principal vector of cocoa swollen shoot disease (the mealybug, Pseudococcus njalensis Laing) by decreasing the populations of its attendant ants1.

Natural Sources of Rubber

AN interesting note on possible West African sources of rubber is contributed to Farm and Forest (3, No. 2, June 1942) by J. H. Mackay, the general editor, who is on the staff of the Forest Department, Nigeria. Latexes vary in the proportion of resin and caoutchouc they contain, the more resinous providing the bird limes of the West African native. 'Ate', the coagulated latex of the vine Carpodinus hirsuta, has been in demand since the outbreak of war for trapping moth pests of stored cocoa, but it was formerly exported as a 'paste' rubber. The latex of Ficus platy-phylla yields the Niger gutta of commerce ; for this a former demand for use in the manufacture of chewing gum shows signs of reviving. It contains some 13 percent caoutchouc. Funtumia elastica is the only indigenous rubber yielding tree ; in 1896 some three thousand tons of rubber was exported from it but the yield fell owing to ruthless tapping.

Moth Pests in Cocoa and Confectionery

1. The chief pests of cocoa and chocolate are the Pyralid moths, Ephestia elutella (cocoa moth), E. kühniella (Mediterranean flour moth), E. cautella (fig moth), and Plodia interpunctella (Indian meal moth).2. Beans are infested before arrival at the factory, this infestation commencing on the plantation and increasing during the various stages of transit to the factory. The docks, in particular, may be the most important source of infestation owing to the fact that there fresh consignments may be brought into direct contact with much older consignments already heavily infested.3. The steps recommended for factory use are:—(a) General cleanliness in all parts of the factory, avoidance of dead spaces which offer opportunities for breeding and pupation, removal of all waste material, constant sweeping, frequent whitewashing and distempering, etc.(b) Heat treatment of beans on arrival at the factory and subsequent storage where they will not be liable to re-infestation. The heat treatment to consist of subjection to a temperature of 60° C.–65° C. for a time dependent on quantity of beans.(c) The use of traps in the factory in order to keep down the numbers of stray moths. Such traps may consist of vinegar and syrup.(d) The protection of all finished goods by means of fine-mesh materials so far as possible.4. No insect life survives either roasting or any stage of manufacture in which the chocolate is in a molten condition.5. Although parasites exist which prey on the larvae of these moths, it is not considered that extermination by means of them would be practicable.6. Fumigation of warehouses, especially at the docks, is under consideration by the Empire Marketing Board, and any recommendation they may make will probably be applicable to factories. At the present stage, however, it is premature to make suggestions.