18fi 



THE AGKICULTUEAL NEWS. 



JrxE 3, 1916. 



INSECT NOTES. 



THE DISPERSAL OF LEAF-BLISTER 

 MITE OF COTTON. 



The leaf-blister mite has been known a.s a pest of cotton 

 since July 1 90-3, when it made its first appearance in Mont- 

 serrat. There seems to be no doubt that this mite lived upon 

 some wild plant before the revival of the cotton industry, but 

 this has not been proved by the discovery of such a food 

 plant. The leaf-blister mite appeared in all the islands of 

 the Lesser Antilles very shortly after its first discovery, 

 except in Barbados where it was discovered only as late as 

 1912, although the indications at that time were that it had 

 exi.sted for .some tw<j or three years without being recognized. 



The means by which the leaf-blister mite is spread has 



never been definitely settled. It has been believed that 



birds and insects and even the wind may have been agents 



' responsible for its distribution, and it has been believed that 



■ the mite has also been transported from place to place along 



with cotton seed. 



When this pest was found to be established in Barbados 

 a careful survey of its distribution in that island was con- 

 ducted by the local Department of Agriculture, as a result of 

 which it was found that the centre of worst infection occurred 

 along the Leeward coast some 5 or 6 miles north of Bridge- 

 town, and that at the extreme northern and souLheiii tnds of 

 the island it was not to be found; and the sunw is true of 

 the central and south-eastern cotton-growing districts. This 

 showed a definite area of introduction from which the infesta- 

 tion had spread. It was not a general outbreak such as was 

 seen in the other islands in 1903 and 1904. 



In 1914, while observations on the leaf-blister mite were 

 being made in the Laboratory of the Imperial Department of 

 Agriculture, it was seen under the microscope that the full- 

 grown mites had a tendency to ascend to the tips of leaf 

 hairs and assume what appeared to be a waiting position with 

 the legs of the first pair extended as if to attach to any moving 

 object which might come into contact with them. When a 

 hair from a c iniel's hair brush was brought into contact with 

 these insects, it was immediatelygrasped and the mite loosened 

 its hold on the leaf hair and allowed itself to be carried away. 

 This habit and position is exactly analogous to the habit and 

 position ot larval ticks which climb grass and other herbage 

 and attach themselves to cattle and other animals which come 

 in contact with them in passing Any leat-blister mite in 

 this position would attach it.self to an in.sect or bird and be 

 carried away. It may be stated als^^, that at certain times when 

 the mites are crawling about on the surface of the leaves and 

 twigs in considerable numbers they might easily crawl on to 

 the feel of any bird resting for a -moment on the jilant. 



The following note illustrates the disper.sal along with 

 seed. 



Early in the present year an officer of the Imperial 

 Department brought from another island a few seeds of 

 cotton in an envelope. Some time afterwards two of these 

 seeds were planted in soil in concrete tanks covered with 

 carefully buUt cages of fine mesh .wire, so that none but the 

 very .small insects could have access. No cotton had been 

 grown in these cages before and no cotton is grown in the 

 district. 



The first leaves of the plants from the.se seeds showed 

 the characteristic signs of leaf-blister mite attack, and all the 

 secondary growths have likewise been infested, although the 

 first infe.sted leaves were picked oft' and burnt as they appeared. 

 There seems to be no po.'^sibility that the leaf-blister mite 



could have found its way to these plants but by means of the 

 seed, coming with it from the island in which it was grown. 



As a safeguard against the introduction of the leaf- 

 blister mite into cotton fields with the seed used for plantin", 

 the disinfection of the seed in a solution of corrosive .sublimate 

 1 part, in w;itcr 1,000 parts, or roughly 1 oz. of corrosive 

 sublimate in 6^ Imjierial gallons of water is recommended 

 for general practice. 



This treatment has been extensively used by cotton 

 planters in the past as a general means of disinfecting cotton 

 seed and destroying fungus spores that may be present: and 

 row when it seems to be proved that the leaf-bliscer mite'can 

 be introduced with the seed, there is greater reison than 

 before for this disinfection. 



Reafforestation in Queensland. — The following 



outline of an Act has been prepared foi dealing with the 

 question of sustaining the <i)ueensland forests in vigorous 

 growth: — 



'Every peraon owning land to the amount of 10 acres or 

 more shall retain, plant, or cause to be planted, not less than 

 21- per cent, of the whole in forest trees. The trees selected 

 shall be at the owner's discretion, provided that imrlpr normal 

 conditions they may be expected to attain a height of not 

 less than 20 feet and 1 foot in diameter of trunk. Stone and 

 pip trees excluded. The method of planting and reservation 

 may be either as shelter belts, plantations, clumps, or isolated 

 specimens. 



'For computation, the following number of trees may be 

 considered equivalent to a 21 percentage; Isolated speci- 

 mens, an average of not less than three to an acre; clumps 

 (three trees or more, not less than G feet apart), an average 

 of six trees per acre; plantations or shelter belts, an average 

 of not less than seventeen trees per acie planted 4 feet apart 

 or more — equal in all to an average of one tree per S feet 

 square to area planted. 



'In plantations and .shelt(^r belts measurement of area 

 may also be resorted to: in that case the measurements shall 

 be taken (5 feet from the trunk, outside the line of trees, etc. 



'There would be several other clauses necessary, defin- 

 ing the ownership of the trees, prevention of planting ever- 

 green species within a, chain of public road, distance from 

 boundaries, re possible nuisance or damage, etc., too 

 numerous to mention here The Government should also 

 assist by publishing leafiets descriptive of suitable tree.s, 

 their treatment, requirements, etc They should also obtain 

 .seeds of the most useful kinds, and at cost price to bona 

 fide planters.' 



Cassie and its odour forms the subject of an interestiuw 

 article in the Perfuinery and Eafcntml Oil Record for March 

 1916. Cassie pomade has been made for many years 

 from the blossoms of Acu-ia Farnesiana. This species 

 is widely distributed throughout the tropics and is re- 

 garded as a uatii'e of the West Indies. It appears 

 that the flowers have better odour when grown in sub- 

 tropical climates. The pomade is prepareil by the macer- 

 ation proce.ss by dige.sting the Howers in melted fat. This 

 process was described in a recent issue of the Arfiicu/tural 

 Nevs. Other species of Acacia have a similar odour to the 

 fiowcrs of A. Farnesi'ina, notably, A. Bertoloni, A. Caivnia, 

 A. dealbata, a native of Australia, and several others. The 

 article gives the chemical and physical characteristics of the 

 essential oil which produces the odour. 



