6 



of a sufficient number of parasites to hold it m check. Added to this 

 is the fact that disastrous outbreaks liave followed mild winters, suc- 

 ceeded by a spring that was below the normal in temperature and 

 more or less stormy. The writer has observed, in the case of other 

 aphides, that seasons of unusual abundance are preceded by cold, wet, 

 and usually "backward" springs. The situation, then, is probably 

 this : The pest is ordinarily kept down by its natural enemies, but 

 during open winters — not sufficiently mild, however, to render these 

 enemies active — it breeds unrestrained, and the exceptionally cold, wet 

 spring enables it to continue breeding while the parasites are still inac- 

 tive ; thus the pest is enabled to get the advantage in point of numbers 

 and work its devastation before the natural enemies can become suffi- 

 ciently abundant to overcome it. 



It can be seen, therefore, that although the fanner's interests are 

 involved, he is unable to determine for himself just what is going on in 

 his fields. He can not foretell the weather months in advance and has 

 no way of knowing when to expect a recurrence of a serious outbreak of 

 the aphis until it is too late to ward off its consequences. The reader 

 will correctl}' infer from the section on preventive and remedial measures 

 which follows that when spring approaches there is little that can be 

 done by the farmer to improve the situation in case the insects are 

 present in great numbers ; but the outlook is by no means the gloomy 

 one that may appear from this statement. Following the spring rains 

 there usually comes, sooner or later, a period of dry, warm weather, and 

 whenever such a period comes the aphides very soon disappear. The 

 reason for this is that their parasites and natural enemies, no longer 

 deterred from activity by cold and wet. immediately begin to breed with 

 extraordinary rapidit}' and bring about their practical destruction. 

 Should this warm, dry period come later than usual, greatei' damage is 

 inflicted by the aphides ; sliould it come earlier than usual, serious 

 injury is correspondingly obviated. 



PREVENTIVE AND REftrEDIAL BIEASURES. 



We reallj' know far too little of this pest to be able to deal with it 

 satisfactoriby. It would seem that the later in the fall grain were sown 

 the less attraction there would l)e for the pest to invade the fields in 

 fall. Late sowing, then, is about the onh' preventive measure that can 

 be suggested. 



On the subje(!t of treatment for these insects tbei-e is not niucli \\\nyv 

 to be said. It is probable that a great manj' of the aphides could be 

 destroyed b}^ rolling the fields as soon as the pests appeared on the 

 leaves in any considerable numbers. Brushing ovei' the fields with a 

 l)rush drag, made by fastening the ends of limbs or bushes in holes 

 )uade in a rail or a piece of 4-by-4-inch timber, might also prove bene- 

 ficial. These two practicable measures are. all that can be advised with 



