APHELINUS MALI.

Timaru Herald, Volume XCVIII, Issue 18084, 23 June 1924, Page 11

APHELINUS MALI.

COMBATING THE WOOLLY APHIS

MR C. H. TRIPP’S EXPERIMENTS

During the last two or three years 'Considerable interest has been aroused amongst orchardists throughout the Dominion in the aphelinus maii (parasite ot tiie woolly upms), winch was introduced into New Zealand by the Cawthron Institute (Nelson) in 1921, to combat tiie ravages' of the, woolly aphis, m apple orchards;. Last season the aphelinus was reared in large numbers, and about 90,000 living insects were distributed by post to all parts of the Dominion, from the Cawthron Institute inseetariuin, without charge to the recipients. Reports from all parts of the country indicate that the parasite is now firmly established, and has done an immense amount of good in apple orchards. Mr C. H. Tripp, fh an interview with a “Timaru Herald’’ representative yesterday, said that Dr Tilliard, of the Cawthron Institute, had sent him 150 aphelinus mali in December, 1922. Mr Tripp had covered a branch of an apple tree (badly infected with woolly aphis) with lino wire netting to keep the birds away, and liberated 100' survivors of the consignment, on that branch. A cold southerly wind came up just afterwards, and a spell of wet weather followed, which Mt Tripp thought had destroyed all tho parasites. He did not see any until November, 1923, but by the following month they had increased to thousands. This year he had caughL and distributed about 500 aphelinus among neighbours, and spread others about distant apple trees, as he found that they had themselves spread amongst all tho contiguous trees. As far as he could say the aphelinus were working great havoc amongst the woolly aphis, which were particularly bad at Orari Gorge, where he had experimented, but he thought it would take several years to eliminate the aphis completely. “In so far as I can gather,” concluded Mr Tripp, “the only _ way in which the aphelinus breeds is by laying its egg inside the woolly aphis, which swells up and dies. The aphelions, which is a very minute wasp-liko fly, smaller than a sand-lly, emerges from the shell of the woolly aphis, when it is fully developed. Hence, when the aphis is killed off, the aphelinus has nowhere to lay its eggs, and naturally dies too.” The woolly aphis and aphelinus arc natives of 'America. Anyone might have introduced the aphelinus but what the Cawthron Institute were so care ful about was not to introduce tho parasite of the aphelinus, and in order to cliviimite the parasites of the aphelinus, the Cawthron Institute guaranteed the aphelinus for a considerable time, and killed off every strange in sect that developed with them. This was the hardest and most important work of the Institute. As an example of want of care in this respect, Mr Tripp mentioned that a few years ago someone heard that a certain species of ladybird was tho greatest natural enemy of the earwig, so he imported a number of ladybirds, but did not quarantine them; heuce he turned nut the ladybirds amongst Iho earwigs, together with the ladybirds’ own parasites, and tho result was tiial a ladvbird could kill an earwig, but before it could do more, its own parasite killed tho ladybird; hence the chances of destroying earwigs with ladybirds was now impossible m New Zealand.