217 



who have hitherto trusted to the control of citrus pests by natural 

 agencies, such as entomogenous fimgi. Though there may be truth 

 in the contention that it pays better to grow the lower qualities of 

 fruit without treatment, than the better ones with treatment, yet 

 the magnitude of the damage due to the weakening of the trees by 

 scale and whitefly infestation is beginning to be appreciated. 



Six species of insects and mites are responsible for 95 per cent, of 

 the damage to citrus trees in Florida. These, in order of destruc- 

 tiveness, are Dialeurodes citri, Ashm. (citrus whitefly), Lepidosaphes 

 beckii, Newm. (purple scale), Eriophyes oleivorus, Ashm. (rust mite), 

 Chrysomphalus aonidum, L. (red scale), Dialeurodes citrifolii, Morgan 

 {Aleurodes nubifera, Berger) (cloudy-winged whitefly) and Tetranychus 

 telarius, L. {sexmacidatus, Riley) (red spider). 



The spraying scheme recommended for the control of these is : — 



I. Paraffin-oil emulsion ; Government formula 1-66 or 1 per cent, 

 of oil, for use in May. The object of spraying at this time being to 

 kill whiteflies, scale-insects, and to a large extent, rust mites, it should 

 be done after the adults of the first brood of whiteflies have disappeared 

 and before those of the second brood appear, the fruit being then 

 an inch or more in diameter. As this treatment is given before the 

 rainy season begins, it does not interfere with the control work of 

 beneficial fungi. 



II. Lime-sulphur solution, 32° Be., 1-50 to 1-75, for use in June 

 and July. The main object of this application being to kill rust 

 mites, it should be applied before they get very abundant and before 

 any russeting appears. 



III. Paraffin-oil emulsion ; Government formula 1-66 or 1 per cent. 

 of oil, for use from 25th August to 31st October. The second spray- 

 ing for whitefly and scale-insects, which will also remove the sooty 

 mould from the trees and enough from the fruits to allow of their being 

 coloured by the sun. Soda-sulphur, 1-50, composed of 30 lb. sulphur, 

 20 lb. caustic soda and 20 U.S. gals, water, may be added to this 

 spray to increase its effectiveness in killing rust mites. 



IV. Lime-sulphur solution, 32° Be., 1-50 to 1-75. for use in Novem- 

 ber or December. The object of this spraying being to kill rust mites, 

 it may or may not be necessary, according to the degree of infestation. 



It is estimated that treatment on these lines of the 1915-16 crop 

 of oranges and grape-fruit in Florida would have increased the net 

 returns by over £250,000. 



IsELY (D.). Orchard Injury by the Hickory Tiger-moth. — U. S. DepU 

 Agric, Washington, D.C., Bufl. no. 598, 4th February 1918, 14 pp., 

 3 plates. [Received 4th March 1918.] 



Halisidota caryae, Harris (hickory tiger-moth), the favourite food- 

 plant of which, in spite of its name, appears to be walnut and not 

 hickory, is also a general feeder on the foliage of deciduous trees and 

 shrubs. These, however, serve as food only for the nearly mature 

 larva, the development from egg to pupa mainly taking place on trees 

 of the walnut and hickory family and on pomaceous fruit-trees. 

 The chief injury by this insect is due to the gregarious habit of the 

 larvae in the early stages, when they may strip branches or even small 

 trees of their foliage, the damage in the latter case being sometimes 



