INSECT PARASITES

New Zealand Herald, Volume LXX, Issue 21578, 24 August 1933, Page 12

INSECT PARASITES

WHITE TOMATO FLY * natural enemy found WAR ON WHITE BUTTERFLY [BY Ti-XKURAI'II—OWN COMtKSPONDENT] \ PALMEKSTON NORTH, Wednesday For many years New Zealand tomatoes have been ravaged by a white fly of unknown origin. Its depredations have been extensive in glasshoiises at Auckland, Christchurch and Nelson. It thrives on leaves to an enormous extent, sapping the juice of the plant, weakening it, besides disfiguring the fruit, which becomes speckled and unappetising in appearance. Following investigations commenced two seasons ago, 3\lr. J. W. Muggcridgo, Government Entomologist at the Plant Besearch Station at Palmerston North, has been successful in establishing a natural enemy insect, which he has bred under laboratory conditions to such an extent that sufficient numbers Hvill ultimately be available to fill all requirements. It is a small, clearwinged insect of the same order as that which is now making war on the cabbage white butterfly. White Butterfly Campaign OucC liberated and established in a glasshouse, the insect is quite sufficient to keep the white fly under control. However, it is susceptible to outside temperatures. To hold it safely over the winter months, it is stated, heated glasshouses are necessary, thus producing the possibility of the need for annual distribution, which may prosent an awkward problem.

Orders to the value of £305 for new season's supplies of the parasite to attack the white butterfly pest this summer have been placed with the Imperial Institute of Entomology on behalf of the Plait Research Station. Plans are now being, formulated in collaboration with th-j Fields Division of the Department of Agriculture for their liberation immediately they corno to hand. .. . Distribution o! Parasite

The superintendent of the division, Mr. W. J. McCullough, states that steps are being taken to establish additional colonies of parasites in the Wairarapa and on the Poverty Bay flats on selected areas in chou moellier or turnip crops infested with the 'white butterfly. The pest has its main breeding groutiels in the east coast districts, where conditions appear to be most suitable for it. Expenditure on the war against the white butterfly has been made possible from two sources, states Mr. Muggeridge. Recently, Hawke's Bay farmers, realising the serious nature of tho menace to crops, raised £lO5 and forwarded it to the DirectorGeneral of Agriculture with the request that it should be expended on parasites for liberation in that district. Authority has just been received from the -Director-General of Agriculture to cable a further £2OO to England for the purchase of insect enemies. No delay has occurred in placing / tho orders. "

The Government Entomologist, however,' has issued a note of warning against undue optimism, as the- problem is not one merely to be solved in «a season. It is intended to liberate parasites as far afield as possible, including the Manawatu district. There is a possibility that the Plant Research Station may be inundated with applications on the assumption that the advent of tho. parasite means the immediate end of the whit'j butterfly: This idea is quite erroneous.

Good Results So Far

"There is no knowing how long it will take to achieve the object," said Mr. Muggeridge to-day. "A great "deal depends upon how the insects respond to the environment. Though there is every ground for thinking that in the parasite has been found one of the main sources of control, 1 would like the people of New Zealand to' view it as an experiment based on sound scientific practice and principles well established in other parts of tho world." The butterfly now had a very strong hold in New Zealand, continued Mr. Mugfreridge. There was every prospect that it would multiply and do extensive damage before it was possible to bring it under control. The parasite bred more quickly than tho butterfly, one alone being capable of producing 700 eggs, while for a single white butterfly the maximum number was about 240. While a recent survey in the field indicated a rapid increase' of the parasite and a high percentage of parasitism, it was certain that the full effects of their liberation would not be secured until there had been a general distribution throughout the whole oi: the affected areas.