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PLANT SANITATION. 



Entomological Notes. 



By E. Ernest Green, Government Entomologist 

 The Tortrix pest (Capua coffeuria) of the tea plant has attracted con- 

 siderable attention during the past month. Loss of crop caused by this cater- 

 pillar has been variously estimated at from 10 to 50 per cent, over certain areas. 

 The Maskeliya and Dikoya districts are more particularly troubled by the Tortrix. 

 A meeting of the Maskeliya Planters' Association (at which the Government 

 Entomologist was present) was held in April, when a resolution was passed calling 

 for united action against the pest. It was decided to concentrate attention upon 

 the collection and destruction of the egg masses. If this is properly and systema- 

 tically carried out by concerted action of all the interested planters, it can 

 scarcely fail to check the pest, more particularly as the caterpillars themselves 

 are being attacked by the Ichneumon parasite described in the June and figured 

 in the July numbers of this Journal (Vol. XXV). A careful examination of the 

 caterpillars in the field showed that 16 per cent of them were attacked by this 

 parasite. There were no signs of fungal disease amongst the caterpillars ; but this 

 was scarcely to be expected after such a prolonged drought. Combination is the 

 most important ingredient in the recipe. The eggs must be simultaneously collected 

 on every infested estate, or the good effects will be very largely nullified. An 

 interesting point was brought out during the discussion, namely, that the time 

 of egg-laying varies in different localities, being later in the upper end of the 

 district. On this account it is very important that returns of the collection of egg 

 masses on different estates should be recorded and tabulated. At the time of my 

 visit fresh egg masses were being collected on estates at the upper end of the 

 district, while in mid and lower Maskeliya the eggs had all hatched out some 

 ten days previously. 



In addition to the Ichneumon parasite, the larvae of one of the wasp-like 

 hover-flies (Syrphidae) have been observed to prey upon the young Tortrix cater- 

 pillars. Various species of Aphidaa form the usual food of these fly larvae, but 

 when Aphis is scarce they will turn their attention to other soft-bodied insects. 



Specimens of tea leaves badly attacked by the ' ribbed mite ' (Phytoptus 

 carinatus) have been sent in from the Nuwara Eliya district. The pest appears 

 to be at its height at the present time. The leaves are tinged a dull coppery purple 

 and dusted with the minute white cast skins of the mites. Under the micro- 

 scope the living mites can be observed in vast numbers. With the advent of 

 the south-east rains, this pest will rapidly abate. But failing this natural cure we 

 have a specific in powdered sulphur. 



A correspondent sends me specimens of a ' nettle-grub ' from the Yatiyan- 

 tota district with the report that they are causing extensive defoliation on 

 several fields of tea. The species is either Thosea recta or Thosea cana, the 

 caterpillars of which are almost indistinguishable. It is a small oval green slug- 

 like caterpillar with tufts of greenish urticating hairs on each side. When full 

 grown it constructs a compact egg-like cocoon attached to a leaf or a twig. Unless 

 the pest is discovered before a large area is involved, hand picking is of little 

 use to check the attack. The only satisfactory treatment is to prune the infected 

 fields and burn the prunings together with all fallen leaves and rubbish from 

 beneath the bushes. This may seem an heroic remedy ; but, unless it is under- 

 taken, the caterpillars will do the pruning themselves, and will have time to 



