92 [ DISEASES OF CITRUS TREES 



TREATMENT OF CITRUS TREES INFESTED BY SCALE 

 INSECTS. In the case of the fluted scale (Icerya Purchasi) 

 no treatment is necessary beyond colonizing a few 

 Australian ladybirds (Novius cardinalis] which is its 

 natural enemy, and fortunately a very efficient one. If 

 the infestation happens to be of old standing, and 

 very severe, this ladybird will establish itself the more 

 readily, and perform its work more thoroughly. 



Other scale insects have of course other natural 

 enemies, and these are often sufficient, but severe 

 attacks which threaten the trees with exhaustion, such 

 as a generalized attack of Chrysomphalus or Mytilaspis or 

 Lecanium or Parlatoria, will require energetic treatment. 

 A scale insect newly established in a district, is at 

 first unmolested by the natural enemies which keep 

 the other scale insects in check, and therefore often 

 assumes an alarming virulence, and may cause much 

 injury both to the tree and to the fruit, before the natural 

 equilibrium is restored. In these cases the cultivator 

 should not wait inactive to see the outcome of the 

 struggle between the tree and the parasite, the result 

 of which is always disastrous to himself. 



It will be a tedious and useless task to describe 

 the many methods of treatment which have been 

 recommended against the scale insects, as many of them 

 have never been adopted on a considerable scale, and 

 others have been tried with indifferent results. The 

 following summary of the more rational and practical 

 measures will be found sufficient for a work of this 

 nature. 



To begin with, the vigour of the trees should be 

 kept up by good cultivation, by the proper use of 

 manure and fertilizers and by careful irrigation. The 

 grove should be submitted to a fairly heavy pruning, 

 reducing the number of twigs in order to admit air 

 and light into the interior of the tree, at the same 

 time sparing large branches and avoiding large wounds. 



