CHAPTER X 

 FERN FOES AND REMEDIES 



As in every case where plants are grown under glass vermin of 

 various kinds are sure to make their appearance, it is as well to 

 devote a short chapter to the methods of dealing with them. 

 The principal foes we have in our mind are Green-fly, Aphis, 

 White-fly, A leyrodes vaporaria, and the Weevil, Otiorhyncus sulcatus, 

 plus, in houses where artificial warmth is provided, Thrips. The 

 presence of Green- fly is almost invariably due to insufficient ventila- 

 tion or overshading, which induces a tenderness of growth and un- 

 healthy conditions ; healthy plants appear fully capable of resisting 

 their attacks. The first remedy is therefore better ventilation, 

 avoiding draughts, and an increase of light if possible. In this 

 latter connection removable blinds are better than fixed ones, 

 since the more daylight there is admitted the stronger the growth, 

 and shading is really only necessary against blazing hot sunshine 

 and during the warmest months of the year. The second remedy 

 we shall come to later. The White-fly is a terrible infliction when 

 once it is allowed to obtain a footing. This is a fly, really of a very 

 light lemon colour, which flits about snipe fashion from plant to 

 plant when disturbed, and has a clever knack of alighting on the 

 under side of the fronds at a point distant from its apparent point 

 of settlement. Its flight, too, is remarkably swift, and as we have 

 indicated, erratic. This fly attacks both deciduous and evergreen 

 Ferns, but only lays its eggs on the fronds, so that those laid on 

 deciduous ones are eventually cleared away and the following 

 season's brood only arises from those left on persistent ones. Its 

 attack takes the form of a gnawing away of the epidermis or skin 

 of the foliage, the result of which is tortuous lines of dirty white, 

 which in bad cases pervade the fronds entirely and weaken the 

 plants considerably. The eggs, in cold houses, hatch out about 

 April, when the larva? or immature flies may be found on the backs 

 of the discoloured fronds as tiny whitish insects, already busy with 

 their gnawing, and capable of creeping to fresh fields and pastures 

 new on the same Fern even at this stage, though their wider ex- 

 cursions are deferred until May, when after a short chrysaloid 



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