40 APPLIED ENTOMOLOGY 



fall is the best time. Sometimes disking with a harrow can be done 

 where plowing cannot, and is of value. 



Time of Planting. This is sometimes of importance as a protection 

 against pests. Thus, in general, wheat sown after September 20 will 

 escape the attacks of the Hessian fly : early planting will often give 

 cotton an opportunity to obtain the greater part of its growth before the 

 boll weevil has progressed far in its ravages, particularly if early maturing 

 varieties of cotton are planted. It follows from this that a choice of 

 the variety to plant is also often of importance, and insect-resistant 

 varieties of our various crop plants and trees should be selected as far as 

 any are known, if they are otherwise satisfactory. The " bugless potato," 

 while perhaps non-existent, expresses an idea which should be kept in 

 mind, and resistant varieties of plants should be watched for and 

 preserved. 



Trap Crops. In some cases trap crops can be made use of to advantage. 

 A small patch of kale planted in the fall, or of mustard planted early in 

 spring will attract the Harlequin cabbage-bugs as they leave their winter 

 quarters, and on these they can be destroyed, as they seem to prefer 

 such plants to the young cabbages. Several similar cases are also known 

 where trap crops work well. 



Hand Picking. In some cases, where the pest is large, easily seen, 

 or not present in large numbers, hand picking is the easiest method of 

 control. Egg clusters are often of such a color, size, or have such notice- 

 able features that they are not difficult to find, and the convenience of 

 destroying several hundred eggs at a time, as compared with killing the 

 same numbar of insects after the eggs have hatched and the young have 

 scattered, is evident. Larvae feeding in groups together are also often 

 most easily destroyed by hand picking. 



Repellents. Inert materials, such as air-slaked lime, flour, or even 

 fine road dust, thickly spread over plants will, in certain cases, act as 

 repellents, driving insects elsewhere to a greater or lesser degree. Car- 

 bolic acid, naphthaline, oil of citronella, and other materials having an 

 objectionable odor act as repellents to some insects. 



Trap Lanterns. These have been quite extensively tested, but have 

 failed to be as successful as was expected. Though many insects are 

 attracted to such lights, the greater number are found to be beneficial, 

 while of the injurious kinds a large number have already laid their eggs 

 and are therefore no longer of any importance, and most of the serious 

 pests are not attracted at all. On the whole it is doubtful if the use of 

 trap lanterns ever pays. 



Burning Insects. Gasoline torches for burning egg clusters, cater- 

 pillars, scale insects, etc., on trees, have also been tried, but the time 

 necessary to kill the insects in this way is often long enough to injure 

 the tree where the blast hits it, and this method must be regarded as at 



