94 



CONTROLLING INSECTS AND DISEASES 



Timeliness in spraying is fully as important as thoroughness. 

 Chewing insects must be killed before they have destroyed much 

 of the foliage, otherwise the crop may be seriously damaged. 

 Sucking insects must not be allowed to seriously weaken the plant 

 before they are brought under control. Fungous diseases must 

 be checked before they have gained serious headway, if satisfactory 

 results from the spraying are to be secured. 



In all spraying the right material must be applied at the right 

 time for the given enemy. 



Fig. 52. — Sprajnng muskmelons with three-row, gearcd-power spraj-er. 



QUESTIONS 



1. How may rotation of crops be made a means of avoiding loss from the 



attacks of insects and diseases? 



2. What should be done with the refuse from a crop infected with a fungous 



disease? 



3. What is the relation of time of planting to insect injury in certain cases? 



4. How may individual plants be protected from insects by mechanical 



means? 



5. What is meant by a 'Hrap crop"? 



6. What insects may be killed by poisoned baits? How is the poisoned bait 



prepared? 



7. What insects are sometimes controlled by repellants? What materials 



may be used as repellants? 



