THE WHITE FLY

Nelson Evening Mail, Volume LXIV, 20 January 1931, Page 2

THE WHITE FLY

METHODS TO DEFEAT IT INTRODUCTION OF PARASITE TO NEW ZEALAND “The White Fly, its History and Method of Control,” was the subject of a lecture given by Mr D. Combridge, N.D.H. (N.Z.), to a meeting of the Christchurch Tomato and Stone Fruit Growers’ Association. He also gave a very interesting explanation of the parasite to be introduced to New Zealand to combat white fly, and spoke hopefully of its probable success. Mr Combridge pointed out that the white fly was found on many “host” plants in the open as well as about , a dozen greenhouse and cultivated plants. From the time the eggs hatched on the underside of the leaves of the “host” plant attacked, the larvae began by feeding upon the sap of the plant. It passed through the subsequent stages in a period of about 33 days. It exuded all the time from it excrement on the lower leaves and the fruit, upon which a black mould formed, necessitating the cleaning of the fruit before it was possible to market it. It also caused the leaves to fail in their functioning. The female fly Taid its eggs at the rate of five a day, and had a total capacity of up to 120 eggs. There were four or five broods per annum, so that it was cleany seen what the amount of damage would be following the first appearance. Control methods consisted of fumigating. Three methods of that were explained. The first was the jar method, 1 using cyanide of potassium and sulphuric acid in correct proportions. The * dangers and possible misuse of the method were fully explained by the speaker. The second method was the power method, by disseminating hydro-cyanio acid gas throughout the glasshouses. This, he said', should be carefully handled. The third method explained was fumigating with a liquid white fly death, the base of which compound was called tetrachlorethane, first discovered by Dr. L. C. Lloyd, of the Chestnut Experimental Station in the Lee Valley tomatogrowing centime in Great Britain. At that centre over 1000 acres were devoted to tomato-growing under glass. The safety and ease of the application of this compound were explained, and comparative. costs were given. Mr Combridge concluded by giving information regarding the discovery and < culture of a natural parasite that was an enemy of the white fly, and kept it under complete control. The parasite was a small wasp, Encarsia Formosa (Gahan), discovered and sent to the Royal Horticultural Gardens at Wislev. Its distribution to Canada and other parts of the world was dealt with, and Mr Combridge gave the meeting the assurance that news had been received in New Zealand that a consignment of the parasite would arrive at an early date, to be used to ' combat the pest in the Dominion. The relation of the wasp to its host, its rapidity of action, when oviposition took place, and its ability to spread from one glasshouse to another made it hopeful that this pest would be wiped out within the next five years, just as woolly aphis and many of the scale insects had been during recent years.