righting Pests With Parasites.

Otago Witness, Issue 2308, 26 May 1898, Page 8

righting Pests With Parasites.

The greatest single industry of California is frait-growmg, antJ the importance of this industry his s led to the otndy oi every mtt'acd

"which would increase its pt'tfic? or ksstti its expenses. In these studies that- of economic entomology has>takeu a ixrercosE \'lnie, for the moat obdurate and expensive enemy , the orchardisfc has to combat -is the ra.vriad insect' ps'ais that attack him at every point and lessen his profid3 o« all sides. The result of years of careful s'cvi.?y and cou» tifcuouß fighting with spraja &£.'<J washes and

! gases is what may be ctlied fcho Caijft.tnia. method — thivt; of fighting icsects with insects — I a sort of hotcceopathic remedy of like curing J like. Wherf-vtr insect psste have become destructive, tfliorta to find and introduca their natural parasites have been made, and usually ■with good results. Artificial method's are

reaorted to as & temporary expe-iu ai m.til

better means could bo had. Throughout all Nature there cxi»(« a pa Feet system of checks and counter (shrck*, a«u otherwise redundant life is kept down ami the bulanec preserved. It is this fact that the Calif ornians endeavour to take advantage oi. The worst pests that are known there are all imported varieties. They were brought into her bordet s when California, ambitious to become the garden cf the union, imported ail varieties cf plants from every part of the world. In very many cases they were destructive varieties of insects without their natural parasites. Removed from their natural enemies these pests increased with wonderful rapidity and became a threatening danger. One of the worst of these was the now well-

known cottony cushion scale (Icerya purchasi), which at one time threatened the total destruction of the orange orchards of the Stats. All artificial methods of combating this pest were unavailing. At last it was suggested that, inasmuch as the scale had been brought, from Australia, vf here it was native and not a pest, there muht be some natural parasite which kept ib in check. Upon this suggestion action was taken, and the now famous Vedalia cardiualis was introduced. The result of the labours of this one little parasite is that California will this year chip 12,000 carloads of oranges, whereas ebe would have had none had it not been for it 3 labour, for the shipments at one time fell to 600 cars, and scores of orchards were being cut down and burned. The wonderful success of this importation of parasitic friends led to the further study of parasitism in insects, which wa3 aided by the State, and large importations of parasitic insects have been made, with varying but usually good results. In some cases parasites have been introduced with the scales themselves, and in these caaes the spread of the pest has not been

rapid. In other cases natural parasites have adapted themcelvea to new condition?, and attacked the imported insects. There are now very few scale insects in California which do not have some parasites. There are sections, however, ia which the' parasites have not got a foothold, and the peels increase rapidly, while in some casss the scale increases beyond the power of the psr&site to keep it in check. But as a rule the effort to introduce and propagate beneficial insecte has met with marked success. While artificial methods of fighting pests have still to be resorted to for come varieties and in seme sections, these have been and are still being lessened, much to the benefit of the fruitgrower, by taking advantage of Nature's methods of keeping them in check. — Sydney 'Mail,