DISEASES AND PESTS OF THE MAIZE CROP 



4i7 



all, of their food materials directly from the plant on which CHAP, 

 they grow, thus obliging the host to provide food for two, X " 

 when it is constructed to feed only itself. Under this head 

 come the smuts, which have already been discussed, as well as 

 certain weeds such as the is-ona or witch-weed which are con- 

 sidered later (IT 388). 



375- Non-parasitic Weeds, on the other hand, starve the 

 young plants by robbing them of light and air, and indirectly of 

 their provision of food and moisture. A farmer cannot profit- 

 ably grow both weeds and maize on the same land at the same 

 time; in ninety-nine cases out of a hundred one or the other 

 will suffer, and that one will be the maize, inasmuch as a weed 

 is a weed because it is usually hardier than the crop that it 

 infects. 



The principal non-parasitic weeds are of two sorts : — 



(1) Those which are Perennial, or continue from year to 

 year by means of a persistent root-stock which keeps alive, 

 though often dormant, through the winter. 



(2) The Annual weeds, or those which die in the winter 

 and are reproduced again next year from seed scattered in the 

 preceding autumn. 



376. Perennial Weeds. — From one point of view perennial 

 weeds are the most difficult to eradicate, but as they can be 

 dealt with during the dry winter months, when other agri- 

 cultural operations are largely at a standstill, they are, in a 

 way, more easily disposed of than annual weeds. 



The most pernicious perennial weeds are : Bermuda quick- 

 grass (Cynodon Dactylon), and uintjes {Cyperus esculentus and 

 C. rotundus). Two others also threaten to become troublesome 

 in South Africa, viz., bindweed {Convolvulus arvensis) and 

 sorrel {Rumex Acetosella), but up to the present time we have 

 not met with them in the maize crops. Khaki-weed (Alternan- 

 thera Achyranthd) and bachelors' buttons {Gomphrena globosa) 

 appear from their habit less likely to become injurious. 



377. Annual Weeds. — The annual weeds grow, on the 

 High-veld of South Africa, almost exclusively in the wet 

 summer months. When the rains fall at sufficiently long 

 intervals to allow the soil to dry out thoroughly, the weeds 

 can be kept down with the horse-cultivator. It often happens, 

 however, that the rains fall so continuously during the height 



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