DISEASES OF CITRUS TREKS ] 93 



This thinning out of the twigs and foliage is especially 

 needed in very sheltered situations, where owing to 

 defective circulation of air and the superabundant foliage 

 the larvae of the scale insects are not easily shaken 

 off the tree by the summer breezes. Pruning will also 

 protect the tree from the excessive exhaustion provoked 

 by the attack of scale and will ensure a speedy recovery. 



It is known that a shower of rain when a brood is 

 hatching will wash down many thousands of larvae 

 from the tree, and therefore as a rule severe infestations 

 in spring or autumn are rare if the weather has been 

 showery. Accordingly, it was proved that a good 

 spraying with water, repeated for each brood, has the 

 effect of reducing greatly the number of scale insects 

 particularly of the armoured scales, whose larvae cannot 

 find their way back to the tree. This method may 

 be recommended wherever there is available a water 

 service under pressure, as apart from the initial cost 

 of installation, the expense for each treatment would 

 be negligeable. 



Perhaps the methods of treatment which are 

 receiving increasing attention in all the Citrus growing 

 countries consist in spraying the trees with liquid insecti- 

 cides, and of these the sulphur-lime wash is that more 

 generally used and gives the best results against the 

 armoured scales, such as Chrysomf>halus dictyospermi 

 Mask, Aspidwfus Hederae Val., Parlatoria Zizyphi 

 Lucas, and Mytil>ispis citricola Mask. The mixture 

 made according to the directions of Prof L. Savastano is 

 generally known to be very efficient against the scales 

 and quite safe to the tree. It is easily prepared by the 

 cultivator, and contains the maximum percentage of 

 sulphides, which are the active element of the mixture. 

 It is first necessary to prepare the condensed mixture, 

 which is made by dissolving 10 kilog. of quick lime 

 (unslacked) in 100 litres of boiling water, over a fire, 

 and then adding 20 kilog. of flowers of sulphur, in the 



