20 REPORT OF THE STATE ENTOMOLOGIST I92I 



were rather common June 20th in the latter area and at that time 

 a very large proportion of the developing tassels upon early corn 

 contained from one to five or six or possibly more young larvae, 

 and yet no sign of the insect was observed in the Schenectady area 

 until a female was captured June 30th, and it was not until July 

 14th that a scattering infestation of young larvae was found in one 

 of the earliest corn fields. The maximum infestation that season 

 hardly exceeded 5 per cent, though it should be remembered that all 

 this area had been thoroughly cleaned up in the spring and the 

 infestation must have therefore been greatly reduced. 



A special appropriation of $5000 in 1920 made possible an inten- 

 sive study of the infestation in the Schenectady area and although 

 repeated examinations were made of various plants in and about 

 many infested corn fields, there was no undoubted evidence to 

 show that the European corn borer breeds in this State in any 

 plant except corn. Partly grown to full-grown borers were found 

 in some weeds and grasses in this State but always in or close 

 to infested corn fields and under conditions which led one to con- 

 clude that they were wanderers from the corn rather than that eggs 

 had been laid and the insects developed on these other plants. This 

 infestation has invariably occurred only toward the end of the sea- 

 son and upon such a small scale and under such exceptional condi- 

 tions that broadly speaking, it may be considered negligible, so far 

 as the distribution of this insect from New York areas in plants 

 other than corn is concerned. The infestation of other plants 

 appears to be determined in considerable measure by the density 

 of the insect population, since investigations the past season in the 

 more badly infested Canadian area with its single generation 

 showed that a considerable number of plants near the infested 

 corn were entered by borers toward the end of the season, though 

 there is no record even under such conditions of development from 

 egg to full-grown larvae upon any plant other than corn. 



The borer attacks all varieties of corn and injury is most likely 

 to be serious in the small and medium varieties, mostly because the 

 larger types of corn can maintain a greater number of borers with 

 less likelihood of severe injury. It was also evident in connection 

 with this investigation that the earlier fields of corn were much 

 more likely to be infested than those planted later. 



The above should be compared with the well-known food habits 

 of the insect in eastern Massachusetts. There it breeds freely in 

 barnyard grass, beggar-ticks, cocklebur, and probably a few less 



