GARDEN PESTS IN NEW. ZEALAND 



OVERCROWDING. The tendency to overcrowd, especially in house- 

 hold gardens, is to be avoided ; a favourite habit is to plant something in 

 every available space. Under such conditions pests and diseases will 

 abound, and before attempting to spread over a large area, and so lessen 

 the effect of their depredations, they concentrate in mass formation 

 within the confines of the garden as long as the food supply lasts; 

 further, plants tend to be less vigorous and more susceptible to infesta- 

 tion under crowded than under more open conditions. 



INJURY TO PLANTS. Care should be taken not to injure plants with 

 garden tools during cultivation, and a clean cut should always be the 

 object in pruning. Mechanical injury opens the way for infestation by 

 diseases and some insects. 



GARDEN SANITATION. Clean gardening is an extremely important 

 control factor. In most gardens there are rank growths of grass and 

 weeds in out-of-the-way places, along boundaries, and bordering culti- 

 vated plots. Such growths, especially when the weeds .are related to the 

 garden plants, are always favourite breeding places for many pests that 

 move on to cultivated plants immediately they appear above ground. 

 If these growths are cut and burned in the winter, and the ground 

 thoroughly dug, many a spring infestation will be suppressed by the 

 control of hibernating pests; it is the control of spring infestations that 

 will save a great deal oi' trouble throughout the summer and autumn. 



The compost heap, where garden refuse is dumped until sufficiently 

 rotted, may be a source of infestation; not only does it attract and 

 breed many destructive underground pests, but it may be infested with 

 the spores of diseases harboured by the plant refuse of which it is com- 

 posed; it is thus a ready means of reinfesting the soil. Diseased and 

 pest-infested refuse should be burned without delay, and only healthy 

 refuse used for the compost heap if not dug into the ground, where it 

 will rot. 



CROP ROTATION. Growing the one type of crop on the same piece 

 of ground for several seasons encourages the development of pests and 

 diseases; but by a rotation of different kinds of plants the continuity 

 of the conditions favourable for the pests and diseases is broken, and 

 the latter do not have the chance of becoming thoroughly established. 



DISEASES SPREAD BY PESTS. It should be borne in mind that the 

 fewer the animal pests, the less chance there is for diseases to spread. 

 It is now well known that many pests, though not necessarily epidemic 

 themselves, are carriers from plant to plant of certain destructive 

 fungous, bacterial and virus diseases. 



CO-OPERATION. In a locality of many gardens a co-operative spirit 

 is essential, since a single neglected garden in an otherwise well- 

 managed locality will be responsible for discounting the labours of the 

 neighbours. 



(b) Use of Chemicals. 



Chemicals are essential in the control of pests and diseases, and are 

 applied either in the form of sprays or dusts. The former method is 

 the more usual in this country, but where the water supply is poor dusts 

 tend to take the place of sprays. Chemicals used for horticultural 

 purposes are of two distinct kinds those for the control of animal pests 



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