WHITE BUTTERFLY.

Star (Christchurch), Volume XLIV, Issue 365, 5 March 1932, Page 15

WHITE BUTTERFLY.

Danger of Introduction to South Island. THRIVES ON GROWING CROPS. The small white cabbage butterfly which has been flitting over the North Island in increasing numbers in the past two years has become a serious menace to farmers, orchardists and market gardeners, because of the great damage it does to growing crops, and though it has not yet been seen in Canterbury, grave fears are entertained that it will be introduced unless stringent measures are taken to keep it out. First seen in New Zealand in tbe vicinity of Napier in 1930, this white visitor, which has a wide range and travels with the wind, has since appeared in both Wellington and Auckland. I thrives on cabbage, cauliflower, radish, mustard, mignonette, nasturtium, water-cress, shepherd’s purse, stink-weed, lettuce, turnip * and rape plants, but it shows a decided preference for cabbages and cauliflowers. The pests increase very rapidly and there are five generations a year in New Zealand. One female may lay several hundreds of eggs, which hatch out in from three to five days. Biological control of the pest can be obtained up to a limited extent by means of two parasites, “ Petromalus puparium,” and “ Apanteles glomen* atus.” These parasites are usually scarce in the spring, but they gradually increase during the year, giving from 60 to 80 per cent control later. A contagious bacterial disease, “ Micrococcus pierichs,” known usually as “ wilt,” destroys large numbers In some seasons. Tomato Crops Affected. Though it is effective in attacking the white butterfly, the disease “ wilt * affects tomato crops. Recently a Christchurch grower forwarded a number of diseased tomatoes to the Department of Agriculture for examination. The Department’s mycologist reported that the symptoms of the disease resembled those for “ Australian Spotted Wilt,” a virus disease recently investigated in Australia.

Discussing the matter yesterday, Mr C. E. Pope, president of the New Zealand Tomato, Soft Fruit and Producers’ Council, said that although 3 grave warning was given by Dr D. Miller, entomologist at the Cawthron Institute, Nelson, in December, 1930, concerning the dangers of the importation of noxious insects and diseases, little heed seemed to have been taken of it by the Department of Agriculture.

As a result of the laxity of the Department in enforcing measures for keeping the Dominion free from such pests and diseases, the primary producers were now menaced by the dreaded white cabbage butterfly (Pieris rapae). The destructive character of this pest was shown in the

way in which it eliminated crops. Not only would fruitgrowers and m'arket gardeners suffer from the ravages of the butterfly, but sheepfarmers would also be affected because of the way it attacked rape crops. “ The Government has taken steps to stop the introduction of anthrax,” Mr Pope continued, “ yet it allows a pest to come in which is capable of causing untold loss to the farmer. As soon as this information reached the Stone Fruit and Tomato Growers’ Association it passed a resolution urging the Government to import the parasite ‘Apanteles glomeratus.’ This has been done, but it will be only slightly effective, as it is late in the season before it appears. By that time the butterfly has had time to establish itself, and it is quite late in the season before a control of 60 per cent is obtained. From all accounts the pest seems to be uncontrollable.” The Fruit Fly. There were other diseases and pests which threatened the position of the New Zealand producers, said Mr Pope. All export markets would be in jeopardy if the dreaded fruit fly made its appearance again in this country. Through the prevalence of the fruit fly in Australia the South American market was closed against the exports of Australian apples. The South American market offered a wonderful oppor-

tunity to the apple exporters of the Dominion, for the reason that the large varieties for which there was no demand in Europe were readily disposed of there at favourable prices. The authorities in Argentine were so keen to keep out disease that they placed an embargo on New Zealand fruit for a time and sent two entomologists here to make certain that the fruit fly had not made its appearance. Not until these two entomologists had made their investigations and reported to their own authorities was the embargo removed. The thousands of pounds that the New Zealand Government had spent in controlling diseases and insect pests could, he considered, have been saved if effective precautions had been taken in the first place, as all the destructive diseases had been imported. After September 1 the importation of Cook Island oranges was stopped by the Government because of the risk of bringing in the fruit fly, but the Government allowed Australian fruit to enter at any time from fly-infested areas. Another New Pest. Not only were New Zealand growers menaced by the fruit fly in consequence

of Australian imports, but there was a serious danger of the introduction of

“ thrips.” This was a comparatively new pest 'which had played havoc with the fruit crops of Australia this season, and two years ago it destroyed almost the entire apple crops in Victoria. The pest had caused so much concern to the Australian growers that on February 10 a conference was held to consider what could be done to combat the problem, which was now recognised as the major problem confronting the fruit industry in Australia. Those growers who had suffered considerable financial loss and damage to their orchards through fireblight must take a very serious view of the

“ thrips ” menace, because if the pest became acclimatised to New Zealand their very existence as growers would be at stake, declared Mr Pope.