£100,000,000 DISEASE BILL

Sun (Auckland), Volume IV, Issue 956, 26 April 1930, Page 32

£100,000,000 DISEASE BILL

Great as is the damage inflicted on plants by insect pests of various kinds, the mortality resulting from fungoid diseases is even greater. It is no exaggeration to say that every species of plant falls a victim at some time or other to disease, and it has been estimated that among farm crops alone the loss suffered from this cause annually totals the enormous sum of over £100,000,000. One frequently hears the statement that, under modern conditions of cultivation, plants are more prone to disease than in the past, but it is very doubtful if this belief is justified. The fact is that many more diseases are now recognised as being due to fungi than formerly, for the reason that greater attention has been paid in recent days to the detailed study of these organisms. It is only within the last hundred years or so that the real nature of the various blights, mildews, and rusts which affect so many plants has been recognised for what they are. Previous to this, such plant ills were regarded as due either to bad weather, unsuitable soils, or “acts of God.” That fungi can only grow and flourish under damp and fairly warm conditions, that during what is commonly termed “muggy” weather, blights and mildews are most troublesome, has for long been recognised. The inferences drawn from this observation have, however, often been quite erroneous. Thus, Theophrastus, who lived in the latter part of the third century 8.C., and who made a special study of the diseases of plants as then known, wrote: . .The position and character of the land makes no small difference (to the development of disease), for lands which are exposed to wind and elevated are not liable to rust, or less so, while those that lie low and are not exposed to wind are more so.” Even as late as the eighteenth century the belief was held that the causes of the diseases noticed on plants were to be ascribed to the vagaries of the weather—as low temperature, wind, etc., and not till the middle of the last century was it recognised that fungi are responsible. But progress has not stopped short with the discovery of the causes of many plant ills. Year by year increasing efforts are being made. Many of the most destructive of fungoid diseases affect only one kind of crop, and the spores of such a fungus, lying in the soil, are unable to develop unless they come in contact with a plant of the particular species which serves them as host. Thus, the rotation of crops acts as a great safeguard in the garden. Just as warm, moist, stagnant conditions favour a flourishing fungi population, so the presence of sunlight and freely circulating air is prejudicial to this type of parasite. Crowding of plants, particularly in houses, is therefore to be avoided—cultivation in open situations with ample room for each individual, and careful attention to drainage, is the surest method of warding off disease.