ORCHARD PESTS.

Otago Witness, Issue 2623, 22 June 1904, Page 10

ORCHARD PES TS.

THE GOVERNMENT P OTOLOGIST'S

ADVICE.

(Concluded.)

INSECTICIDES.

In regard to the methods advocated for ■eonirolliu'g tho depredahecs of insect idcsls, 0n.9 needs but a general knowledge of the life history of insects and their methods of feeding to be able to devise aa effective l'em&dy for any that may appear. Fcr instance, crops are often severely injured by cater p dial's, which are larvae from some cf tho moth's and buf ternie^. They have jaws, by means of which they can bite off po.rtiona of a lsaf or othe. soft parts of the plant, and, after chewing, digest it mnoh a? would one of the higher animals. To this class of insect the cherry slug belongs, an:l such insects a? feed upon fruits. For all insects of tbis cWs an effective remedy is found in any poison that can be. spread over the leaves in quantities sufficient to destroy the insects without injuring the fcliagc of tiie plant, such, for instance, as any of the arsenical remedies. Another class of insect includes any of the aphi3, or plant lice, that are frequently found' upon the leaves and green twigs of various plants. Instead of chewing their food, they have sucking mouth-parts, through which they draw out the sap of the plants, sinking through the surface layers of the lesueg. Poisoning them by means of any substance placed upon the surface ia not possible. Some remedy must be found that will destroy them by contact with fch& out9ide of their bodies. Effective remedies for the destruction of this class of insects are kerosene emulsion, resin mixture, d'eooction of tobacco and eoap, applied at any time during spring or summer.

Besides the soft-bodied insects mentioned above, w© may also include in this class those known as scale insects, such as the mussel or oyster-shell scale. The lime, salt, and sulphur mixture applied while the trees arc dormant is a most effective remedy for this class of insects. Some insects that cannot be reached by direct application to their food plants may be reached indirectly by poisoning substanoes which they prefar (o their normal green food. The time at which- an insecfe pest can be successfully combated or prevented is in most cases extremely short ; often a difference of a day or two is sufficient to change success into failure. Therefore, when the proper time comes, it does not do to defer until some more convenient season. .Everything else must "take a back scat,'' or tine iu-

sects may have things all their own way, much to the grower's detriment and loss. The following are standard insecticidal remedies, and of well-known efficiency: —

— Arsenical Preparations. —

Of the aboye, Paris green, Kedzie's arsenate of soda and arsenite of lead are without doubt the best. The last is sold under the name of disparane.

— Paris Green.— Practically a good brand contains upwards of 50 per cent of arsenic insoluble and 4 per cent, that is water soluble. This small percentage of soluble arsenio makes it necessary to add to each lib of Paris green at least lib of fieshly slaked lime. The free arsenic is combined with the lime, and the material can then be applied at tho rate of lib of Paris green to 125 gallons of water on ordinary fruib trees, excepting peach trees. The addition of two quarts of thick molasses or glucose, or a small quantity of stock solution of resin mixture, or a little salt, is believed to add materially to the time tho application remains effective, by increasing its adhesive qualities. It is important to also observe that whatever form of arsenite is used ifc should be carefully mixed into a thick paste and thinned before it is added to the water.

— Kedzie's Lime Arsenite.—

This is much cheaper than Paris green, and ifc is also superior, because it remains in suspension in water more than t'hx«<e times as long. Ifc is made as follows: — Boil in an iron pot lib of white arsenic with 21b of washing soda to 1 gallon of rain water, until the whole of the arsenic is dissolved, leaving only a nvL'ddy sediment. The product is an ar^eiiite of soda, which may L' 3 kept in a clorolystoppered jar or bottle till needed, labelled "poison." To prepare for use, slake 2ib of lime, dilute with 2gal water, and add on© pint of arsenic of soda solution ; when tbi<? is combined add water to make 40gal. This is the equivalent cf 4oz of Paris green, and at the rate of lib of Paris green in 160 gal of water. The addition of treacle or molceses, or re-in mixture, or salt, w-11 increase its adhesive qualities.

— Arsenato of Lead (Disp'arane). —

This poison can be prepared according to the formula published in Leaflet No. 10, cr can be purchased in paste form realty prepared. It is applicable to all purposes for which the two preceding are used. It is one of the best preparations of aisei'ie, but far too expensive except for use where only a little work is done.

— Lime, Salt and Sulphur Wash. —

Tbe many tests made during the last {ew year 3 with this wash over a wide area in the United Stares, Australian Colonies, and Now Zealand have shown that it is a standard remedy for the control of scale inseota, su.ch as the San Jose scale and ib& ovs*; •:• shell or mussel scale (sca;y blight). It is roally a lime and sulphur sheep dip -with salt added to cause it to adhere to tho tree-:. It is a disagreeable wa=h to prepare and hardlo, still ibe most efficient of all known tree washes for eradicating the mussel scale. Besides, it possesses fungieidal prcpertdes. pn addition to its inseetiekhl value. Again, it is almost entirely harm less when used in the dormant reason on ell manner of fruit trees. The appearance of the tre&s which have been sprayed with this mixture denotes +bat it is decidedly beneficial to the tree rather than otherwise. Orclxardists have been largely deterred fioai attempting ths. use of t'lis remedy because of the amount of apparatus consido.-ixl necessary for" its preparation and the apparent difficulty in cooking the material successfully, espscially in small quantities. This lias placed tho average fruitgrower re niewhat at a loss how to prepare a;ij handle it. Tho strength of the wash wben properly cooked should show at 60deg Fahr. a specific gravity of about 1052 to 1Q54- en tho ordinary B«aums acid spindle. Of the various formulas which, have been given for the preparation of the lime-salt-and-suio'aur wash, tLe following seems to give the best satisfaction as to strength. It will be noticed that though two parts of lime are sufficient for three parts of sulphur, yet it is considered Lcsb to rcc .mr«nd oqjial parts of sulphur and lime, as the sediment cf llio mixture 'is sprayed with the liquid, '/he addition of salt, besides increasing its adhesive qualities, al»o renders the preeipitita. more flocculeut, and hence likely to give lc«s trouble in the spray pump. Take Lime, unslaked 151b Sulphur (flour) 15ib Salt 51b Water 50gal To obtain the best results in preparing the wash proceed as follows: — Put 4- to 5 gallons of hot w-ater in an iron boiler of 20gallon capacity; add 15ib lime, and well stir to spread it about ; then, as soon as ia full ebullition from slaking, add 15lb sulphur and mix briskly with lime, adding boiling water a^ needed to bring the entire mass into a thick paste. Work the mass into a. perfectly homogeneous paste, then add tho salt, and hot water enough to make 10 or 12 gallons, and boil 30 or 40 minutes. When the v. ash is cooked, which will be denotd by its assuming a reddish orange to rich blood colour, strain through wire netting of fine mesh and dilute with hot water to 50 gallons. When large orchards aie to be sprayed and much material is needed, a steam boiler or cooker will prove economical, because with it several barrels of wash may bo cooked at one time. The boiler belonging to some farm machine could be utilise! to furnish the necessary steam by providing a connection to ndmit the live steam, into the mass to be eoo£2il.

— Limo, Soda and Sulphur Wash. —

Quite recently experiments have Ik. on carried out by several investigators in preparing this wash by a new method without boiling, and where only a few tret-s ai - e to be sprayed for scale, or where, for any reason, ther© is no chance to make the boiled material, the new method may be useful, though more expensive. The following is the formula :— -

Lime 331b Sulphur (flour) 171b Caustic soda ...,»,»«*** 4£lb Water ... M £ £.. 50gal

Slake two-thirds of the lime with water enough to prevent either burning or drowning, and during the process sift over and stir in half of the sulphur; then add the remainder of the lime with more water, and ah the boiling continues stir in the balance of the Sulphur; add water as needed, stirring to help the combination. While the mixture is yet steaming add one-third of the oauetio soda, which will cause a violent boiling, and before this is over add another third ; if then the mixture has not reached a briok-red colour, add tho remainder. If too much water is used at the beginning

or during tli© subsequent operations, it may be necessary to use more toda that the formula calls for to insure the red colour of the. mixture. This k then dilutixl to 50 gallons. If warm water is used in the process the chemical action will develop heat enough to make a good combination, and a perfect spraying mixture will fe&uk. — Sulphide of Pota?h and Lima Wash. —

This wash Las been recently recommended by the- Connecticut Experimental Station, U.S.A. The ingredients are—

Sulphide of potash >r , .w 101b Lime .- ._ ~. 101b

Water L. .'" L. ... ~' ••• '20gal Dissolve the sulphide of potash in warm water, and witli tho solution slake the lime, and' ti.dd water to make up the full amount. The addition of 31b common salt will increase its adhesive qualities. The only objection to it seems to bo its cent, yet in it small place or in a garden ih's would not bo excessive, in view of its simplicity and effectiveness as a ecalo destroyer, to be applied whilo ilia troes are dormant. All the limo and sulphur washes are ©xtremoly useful as winter washes for tha dec-traction of winter stages of insects, such as tho eggs of aphis, bryobia, or lame of ocdliu moth, which commonly hibernate in wounds or undor cracks in the outer bark. — Resin Compound. — Resin - 21b Soda crystal 21i> Soft soap ... lib Water to make lOgal First crush the resin small, boil 2gal water and add the soda, and, while boiling, gradually add the resin, kcephfg the mixturestirred until iho rc*in is thoroughly dissolved, when stir in tho soft soap and water to make' lOgal of spray. This insecticide is invaluable, especially a3 a summer remedy for soft-bodied ineoots, such as scales or aphides.

(To b? continued.)