INSECT PESTS IN ORCHARD NURSERY STOCK.

New Zealand Journal of Agriculture, Volume XVIII, Issue 4, 21 April 1919, Page 216

INSECT PESTS IN ORCHARD NURSERY STOCK.

CONTROL OF RED MITE AND WOOLLY APHIS.

By

GORDON ESAM

Acting Assistant Director of the Horticulture Division

At the Arataki Horticultural Station last winter experiments were undertaken in ' the control of red mite and woolly aphis on nursery stock by dipping and fumigation. Although little benefit was expected from fumigation against the eggs of red mite, it was considered advisable to test its effect on woolly aphis. Two-year-old Munroe’s Favourite apples were selected for the trial. The tests were undertaken on the following lines : —

Lot i : Dipped 22nd July in red oil, 1-6, 1-8, 1-10, 1-12, 1-14. Ordinary dipping, trees being well submerged and then taken out. Some trees were dipped roots and all; others were dipped to groundlevel only.

Lot 2 : Dipped in red oil at same strengths as lot 1. Trees in this lot submerged for three minutes, roots included.

' Lot 3 : Dipped in red oil at strengths same as lot 1, but oil heated to 120 0 F. Ordinary dipping, trees being well submerged (including all roots) .and then taken out.

Lot 4 : Dipped in. lime-sulphur, 1-6, 1-8, 1-10. Ordinary dipping, trees being well submerged and then taken out.. Roots of some trees dipped.

This test was also varied by using a quarter less of sodium cyanide than the quantity of potassium cyanide shown above. All roots were exposed to the fumes of the gas.

The following are observations made on the corresponding lots of trees after planting — ‘

Lot 1.Examined 30th October : Woolly aphis showing on oil 1-8, 1-10, and 1-12. No live red mites on any plot, but eggs looking fresh and red; lighter in colour on oil 1-6 and 1-8. Examined 22nd November : No live mites on oil . 1-6 ; several live mites on oil 1-8, 1-10, 1-12, and 1-14. Examined nth December : No woolly aphis on oil 1-6, but an odd live mite or two. Oil 1-8 showing slight woolly aphis and live mites. Oil 1-10, 1-12, and 1-14, woolly, aphis a good hold. - - ' •

Lot 2.Examined 30th October : No woolly aphis showing except on oil 1-14. No live mites on any plot, and eggs not so fresh-looking as on lot 1. Examined 22nd November : No live mites on any plot. Examined nth December : Oil 1-6, 1-8, 1-10, 1-12, no live mites and no woolly aphis. Oil 1-14, an odd live mite or two and a little woolly aphis. Although all the roots were submerged in- this test the trees made normal growth and compare equally with any of the other lots.

Lot 3. —Examined 30th October : No woolly aphis and no live mites. Eggs duller than on other plots —almost a brown colour. Examined 22nd November : No live mites on any plot. Examined nth December : Oil 1-6, 1-8, and 1-10, no live mites and no woolly aphis. Oil 1-12 and 1-14, an odd live mite or two showing; no woolly aphis. Growth in this lot was in no way retarded by dipping the roots.

Lot 4. —Examined 30th October : All treatments quite a failure. Live mites on the move on each of the three plots. Woolly aphis showing on each.

Lot 5. —Examined 30th October : All fumigations quite unsuccessful. Live mites and woolly aphis on all plots.

CONCLUSIONS.

For the control of woolly aphis and red mite on deciduous nursery stock the tests clearly demonstrated that dipping is quite successful provided the plants are submerged for three minutes in oil at a strength of 1-10.

The failure of ordinary dipping as compared with a three-minutes immersion was very marked.

Heating the oil to 120° F. is as good as the lengthened immersion, but not practical for dipping purposes.

Lime-sulphur, 1-6, was quite inefficient compared with oilin fact, a failure. - -

Fumigation, even used as strong as indicated in (cH), was a positive failure.

There appears to be no danger in dipping the roots in July.

Most nursery stock is lifted and despatched before the end of July. The foregoing trials demonstrated that dipping, in oil is perfectly safe in July. Further tests will be made during the coming months. It is proposed to dip-during the last'week in May, the middle of 'June, and in July, and note whether the earlier'dipping has any detrimental effect on trees and if it will give the same result in the control of pests.

Mowing Weeds.- -A good demonstration of the value of the use of the mower to deal with weed - growths on farm pastures was afforded at Ruakura this season in paddock No. 9. This was cut over early to get rid of the weed silene, or catchfly which had spread over the whole field. The operation was so effective that No. 9 took the position of best clover-field on the farm.

Sublot. Sulphuric Acid. Cyanide of Potassium. Water. Capacity of Chamber. (a.) . . ■ .. f oz. f oz. . 2 OZ. loo cub. ft. (M • • I oz. I OZ. 3 oz. ioo cub. ft. •• I oz. I oz. 3 oz. ioo cub. ft. (c.) . . .. i|oz. l| oz. 4 oz. ioo cub. ft. K) •• . . 2 OZ. 2 OZ. 5 oz. . ioo cub. ft.

Lot 5 : Fumigated 22nd July, as follows