June, '22 Crawford & spencer: European corn borer control 235 



In September especially on land plowed and sown to wheat, they did 

 not migrate much to other fields, but simply disappeared. Spring 

 plowing will kill a large nimiber (how large a percentage is not known) 

 but many mature. If spring plowing is done late, up to within a short 

 time of pupation of the borers, the larvae will emerge after being plowed 

 under. But if just ready to pupate, and then plowed down, they pupate 

 in the stalks under ground and a high percentage of adults emerge from 

 pupal cases, but none of them can reach the surface, from lower than 

 2 inches and the wings of the very few that do emerge are so battered 

 that they cannot fly and soon perish. 



The Futility of Individual isolated cases of cleaning up. 



Unless a com field is a long distance from other corn fields and it 

 shut in by woods, the efforts of individual farmers to control the borer 

 by thorough clean-up methods, are utterly futile. The movement 

 must be community wide, if it is to succeed at all. 



Late Planting. As has been pointed out, moths lay eggs most freely 

 on the earliest sown and consequently the tallest, com. Late planting 

 of the m^ain crop will undoubtedly reduce its degree of infestation. 

 Some corn may have to be planted earlier to act as a catch crop, especi- 

 ally where very large acreages are grown in any one place in the infested 

 regions. Trap crops may fimction if sown in fairly wide strips down one 

 side of a field nearest to last years com field. If this succeeds in at- 

 tracting most of the infestation, it should be removed and fed at once 

 and the waste parts biimed when dry — or destroyed entirely if heavily 

 infested, well before the main crop is harvested. 



These control measures are not expensive to execute. Usually only 

 one field on a farm is involved. Com is such an important crop that 

 the extra care necessary in thorough cleaning up operations will well 

 repay time spent on them and any inconvenience involved. 



Natural Control 



natural factors in the control of the european corn borer. 



1. Natural agencies, weather and winter, killed less than 3% of 

 borers in winter 1920-1921. 



2. In spring of 1920, the tachina fly, Exorista nigripalpis Town, ac- 

 counted for so high as 13% larvae in one field with an average of 8% 

 for that field. For the district an average of 3 or 4% would be fairly 

 true. It cannot yet be considered of much consequence in control. 



3. The insect that probably does more good than any other, is the 

 spotted ladybird beetle, Ceratomegilla ftiscilabris (Megilla maculata) 

 which was repeatedly seen to eat every egg mass it found. These bee- 



