70 tllEVENTIVE Aisri) REAtEDlA-L MEASUllfiS. 



Bhindi is a plant that should be rigidly excluded from cotton areas, as 

 should hibiscus, the roselle hemp [ambadi, skerria, etc.), the holly-hock 

 and a few other malvaeeous plants. If grown they should be grown only 

 where cotton is also growing so as to draw off the pests from it. There 

 is probably a large field for the prevention of pests in this way, but we 

 have not yet obtained the requisite knowledge of Indian insects to be 

 able to make use of it. Equally we do not yet know how to use trap 

 crops to the best advantage. Trap crops are crops grown to lead the 

 pests off from the valuable crop plants. The cultivator who sows mixed 

 seeds in an irrigated plot of land and pulls out half of the plants with 

 caterpillars on has unconsciously used a trap crop and saved his really 

 valuable plants. If he went one step further and destroyed those 

 caterpillars and plants he Avould do still more good and use his trap crop 

 intelligently. There are two ways in which trap crops can be used ; we 

 can sow an early small crop for the insects to eat, sowing the bulk of the 

 field later and destroying the early crop with the insects on or leaving' it 

 until the main crop is well established ; we can sow two crops together, 

 one a valueless crop to act as a bait for insects and which grows only so 

 long as it serves its purposes, being destroyed as soon as it is full of pests 

 or as soon as it interferes with the growth of the main crop. Neither 

 method has been adequately tried in India, though the latter is 

 unconsciously done by cultivators, and in rare cases deliberately; the 

 method deserves to be far more widely tried on an experimental scale. 



The most valuable of our preventive measures after mixed crops is 

 the practice of killing whatever caterpillars are found in crops, when they 

 are few. If cultivators realise that caterpillars are not harmless and that 

 anything that eats his crop may become a serious pest, and if he would 

 but kill these stray insects from the first, the/ would not multiply to 

 the extent that they now do. At present the first brood of insects is 

 never killed, the second is larger and does more harm ; the third eats the 

 whole crop or perhaps emerging next season after hibernation wipes out 

 the young crops. If the first brood were checked, there would be no 

 second or third brood and no loss to the crop. Such a procedure is far 

 more possible in India than in other countries ; the process of picking off 

 caterpillars is one that is not essentially different from the process of 

 laborious hand-weeding and can often be done at the same time^ It is 

 as natural and feasible as weeding, only it has never become part of 

 established usage. Caterpillars are always safe things to kill, though 

 other insects are not, and it is from caterpillars that most of the harm 

 to agriculture comes. 



A common practice which helps crop pests is that of letting stray 

 crop plants grow either at the wrong season or in the wrong field. Stray 



