80 



Oecophyllu smaragdina, F. Rhynchota. Pentatomidae : Bathycoelia 

 thalassina, Schout., Piezosternum calidum, F. ;_ Aphidae : Toxoptera 

 cqffeae, Nietn. ; Coccidae : Stictococcus sjostedti, Ckll., Dactylopius sp., 

 C'ero2)lasles sp. Diptera. Trypetidae : Ceratitis punctata, Wied. 



Insects causing canlcer include : — Rhynchota. Capsidae : Sahl- 

 bergeUa singularis, Hagl. ; Helojjeltis hergrothi, Reut. ; Pentatomidae : 

 Atelocera serrata, Westw., Atelocera sp., Haliomorpha annulicornis, F. ; 

 CoEEiDAE : Pendulinus devastans, Dist. 



The insects that give rise to cankers are among the most widely 

 distributed and the most injurious to cacao ; of these Sahlbergella 

 singidaris, Hagl., is the commonest in the Belgian Congo and 

 sometimes causes the loss of an entire crop. It occurs also in the 

 French Congo, Kamerun, the Gold Coast and Nigeria. In the Gold 

 Coast it is frequently accompanied by S. iheohromae, the two species 

 together causing enormous damage [see this Review, Ser. A, ii, pp. 141 

 and 670]. The life-history of S. singidaris has already been dealt with 

 [see this Revieiv, Ser. A, ii, p. 634]. As a check to the increase of this 

 pest, dead twigs punctured by the insects should be cut out and burnt 

 and the sections smeared wdth coal-tar. The best direct method of 

 control in the Congo is found to be regular inspection of all parts of 

 the plants attacked and the destruction of all larvae and adults thus 

 discovered. This is best done in the early morning. Each worker 

 should carry a vessel containing an emulsion made by dissolving 3-1- lb. 

 soft soap in 2 gals, water to which is slowly added 5 gals, petroleum. 

 This is diluted with 5 parts water to 1 part' emulsion immediately before 

 use. The addition of Bordeaux to this emulsion will act as a control 

 of secondary fungous pests, and should be applied with a brush to any 

 individuals of S. singidaris and washed over any cankers suspected of 

 sheltering parasites. All wounds should be smeared with coal-tar and 

 the canlvcrs with vegetable tar. Recommendations are given as to the 

 best method of planting and cultivating the cacao plants in order to 

 avoid either insect or fungous infestations. It has been found 

 inadvisable to plant cacao on the tops of hills as it is much more liable 

 to attack in these situations ; a better plan is to plant the valleys with 

 cacao and the side of the hill vnih. coffee. Eriodendron anfractuosum 

 (silk cotton-tree) should be eliminated as far as possible on the 

 plantations, as it is on this plant that S. singidaris develops. 



Helopeltis bergrothi, which is a most dangerous enemy of cacao in 

 the East, has not as yet shown great activity in the Belgian Congo, 

 although it occurs in restricted numbers, particularly in the moister 

 parts of the plantations. A considerable increase of this species is 

 considered probable. A key is given to the various African species of 

 Helopeltis. The life-history and nature of the damage of H. bergrothi 

 has already been described [see this Revieiv, Ser. A, ii, p. 671]. Control 

 measures should be undertaken as soon as the insects appear, hand 

 collection being a very successful method as practised by the natives. 

 If the numbers increase, the contact insecticide recommended above 

 for S. singidaris may be used in the proportion, 1 part emulsion to 

 10 or 12 parts water. The food- plants of H. bergrothi in the Congo 

 m addition to cacao are : — Funtumia elastica, Manihot utilissima 

 (cassava), sweet potato, Bixa orellana, castor-oil plant, Cyrtospenna 

 senegalense and an }■ roid found in marshes. Patterson's lengthy list 

 of food-plants in the Gold Coast is also given. 



