Mysterious Habits Of Black Fly: Feared By Farmers

Bay of Plenty Beacon, Volume 13, Issue 41, 14 January 1949, Page 4

Mysterious Habits Of Black Fly: Feared By Farmers

Canadian scientists believe they have at last found an effective answer to what is known as the black fly scourge. If they have succeeded, then the spring of 1949 will be the first in living memory when farmers living within 100 miles of the South Saskatchewan River will not dread the coming of May and June. Every year during May and June swarms of black flies have appeared, doing thousands of dollars’ worth of damage by killing cattle and horses. Farmers would watch the winds closely, for any change of direction might bring with it countless millions of the tiny black flies against which there appeared to be little or no defence. Now agricultural scientists have made a thorough study of the pest, and have mobilised scientific means to combat it. One of the first discoveries in the fight was the source of the black fly. Astonishingly enough, it was found to breed in one river only, the South Saskatchewan—and nowhere else, not even in the tributaries of this river. Then it was found that the rapids were the breeding grounds, the eggs being deposited on the rocks just above the level of the water. Eventually changing to larva and then pupa, the time would come when the fly was fully developed and ready to fly. In some mysterious way, in the hast stages of development each fly would become enclosed in a bubble. Floating downstream in their billions, the bubbles would rise to the surface, burst—and from each would emerge a black fly, to be carried by the wind. Gorge On Blood t In areas miles away from the rapids, swarms of these dreaded flies would suddenly descend on cattle and horses, seeking like mosquitoes to gorge themselves on blood. Until this year, the main method of fighting this pest was a defensive one—keeping the animals in dark barns during the period of-, threatened attack, or greasing them daily with mineral oil or' greases. Then, in 1947, it was thought that DDT might be used to kill the larvae before they could develop. Because of the vast length of , river upon which DDT would have • to be used, the plan was thought impractical. In June, 1948, however, : an aircraft with special spraying , apparatus was used in two tests, to . spray a solution of DDT on the • breding grounds. ( Though the first test was not par- . ticularly successful, the second, us- ‘ ing double the quantity of DDT, j eliminated the larvae for a distance of 100 miles down-stream from the i point of application. The fight, it g seemed, was won. Further tests this year will prove j whether the black fly scourge has been finally brought under control, j