Plant Sanitation. 



120 



[February, 1910. 



Not content with puncturing the pods, 

 it has been killing back the young shoots, 

 with the result that the affected plants 

 have made no new growth and present 

 a very miserable appearance. In the 

 case of young plants (supplies), great 

 improvement has resulted from shading 

 them with palm fronds. It has been 

 decided to spray the older trees with 

 ' Imperial Bar ' Soap Solution, which has 

 been recently used with success against 

 this pest on tea gardens in Assam. The 

 plots of Nicaragua Cacao are the 

 principal sufferers from Helopeltis, and 

 many trees have succumbed to the com- 

 bined attacks of this pest and of ' Brown 

 Borer' (Arbela quadrinotata). 



A study has been made of the insects 

 that normally breed in Cacao pods. 

 Some living but more or less diseased 

 pods were collected from the trees and 

 placed in a close-fitting cage (to prevent 

 contamination from extraneous sources). 

 A surprising number and variety of 

 insects has emerged from them, all of 

 which must have originated in the pods 

 while still on the living tree. It is not 

 to be supposed that they are all actively 

 injurious to the fruit. Many of the 

 Diptera (which have appeared in enor- 

 mous numbers) are probably attracted by 

 decay originated by one of the several 



Eod fungi. Minute Mycetophyllid flies 

 ave been bred out in thousands and 

 have continued to reprodnce themselves 

 in the decaying pods for many weeks. 

 Their larvae are worm-like, but exhibit a 

 distinct head. A. small black species of 

 Chlorodid fly appeared in considerable 

 quantities. I have not been able to 

 determine the larvae of this species ; but 

 it belongs to a family of which the larvae 

 may be actively injurious (such as the 

 leaf and stem miners) or may breed in 

 decaying vegetable matter. Several 

 Tachinid flies that made their appear- 

 ance may be looked upon as friends, for 

 their larvae live parasitically in other 

 living insects. The collection of pods 

 has produced two different kinds of 

 beetles :— a Longicorn (Pterolophia annu- 

 lata), the larvae of which tunnel in the 

 living pods and incidentally afford a 

 passage for other forms of decay ; and 

 a small Anthribiid (Araeocerus sp.), the 

 members of which family habitually 

 breed in seeds and other dry vegetable 

 products. But the most unexpected 

 occurrence has been the appearance of a 

 small ' Clearwing ' moth (Sesia flavicau- 

 data) which has hitherto been considered 

 by collectors as quite a rarity. The 

 emergence of a considerable number of 

 these moths from a comparatively small 

 number of pods— picked haphazard from 

 the trees, proves that this species must 



breed habitually— as a borer— in cacao 

 fruits. 



Other insects associated with cacao 

 that have been noted within this period 

 are : — Caterpillars of Eupterote geminata 

 and Belippa laleana, and two species of 

 Weevils {Episomus lacerta and Myllo- 

 cerus sp.), feeding upon the yoang 

 foliage. 



The "Gardeners' Chronicle" of Dec. 

 25, 1909, has a short note on Prof. New- 

 stead's recent visit to the West Indies, 

 in which it is stated that " Mr. Newstead 

 found on plants of Hevea brasiliensis 

 a night-feeding slug which no one 

 had previously detected, although the 

 damage it occasioned was considerable." 

 A girdle of cotton wool around the stem 

 is recommended as a simple yet effectual 

 remedy. It would be interesting to 

 know if this West Indian slug is the 

 same species (Mariaella dussumierii) 

 that has caused similar trouble in Ceylon, 

 (see T, A„ Nov. 09, p. 43d). The cotton 

 wool barrier may be effective during dry 

 weather (when the slugs are not active, 

 with us), but would be quite useless 

 during the monsoon rains. 



The following extract from the " Al- 

 bum do Estado do Para," quoted in the 

 " India Rubber Journal " of October 10, 

 1909, looks as if the Brazilians are grow- 

 ing alarmed at the rapid extension of 

 rubber cultivation in the East, and are 

 trying to comfort themselves by exag- 

 gerating the severity of the pests against 

 which we have to contend. The "Al- 

 bum" remarks that :—" The highest 

 price obtained by Ceylon india-rubber 

 does not compensate for the heavy losses 

 which that Island suffers from the decay 

 of its tree3 through the all-devouring 

 ' Capin ' (white-ant) aud the defective 

 nature of the soil." As regards loss 

 through the ravages of termites, this 

 statement is absolutely untrue. I do not 

 believe that a single rubber tree in 

 Ceylon has been killed by white-ants. 

 It is true that the stumps of dead or 

 dying trees are sometimes found to have 

 been attacked by these insects ; but, in 

 every case that has been submitted to 

 examination, it has been demonstrated 

 that the tree had been previously 

 attacked by a fungus disease. These 

 diseases, of course, lead to a certain loss, 

 but the deaths from this cause amount 

 to but a very small percentage on the 

 number of healthy trees. I do not think 

 that our "defective soil" requires any 

 elaborate defence. It is admittedly mt 

 so rich as that of the virgin forests of 

 Brazil ; but it has proved itself capable 

 of raising rubber trees yielding from 200 



