66 MASS. EXPERIMENT STATION BULLETIN 189. 



The other economic plants mentioned as hosts of the European corn 

 borer are attacked bj^ the insect only in the absence of corn, or as a result 

 of their nearness to corn in badly infested fields. 



The wild plants mentioned as hosts of the insects are attacked only in 

 the absence of corn, and are not economically important except that 

 they serve as intermediate hosts for the multiphcation of the pest. 



There are two generations of the insect each year. The nearly full- 

 grown second generation larvae pass the winter in a dormant condition 

 within their tunnels, and resume feeding with the approach of warm 

 weather in the spring. They pupate about the middle of May. The 

 pupal period lasts about seventeen days, and the moths emerge the first 

 week of June to deposit eggs for the first generation. A maximum number 

 of 727 eggs was deposited by a single second generation female in life-history 

 cages, and the average number deposited by a single female was 337 eggs. 

 These eggs are deposited in masses from 5 to about 50 eggs, on the under 

 sides of the leaves of the host plant. The first generation larvae hatch 

 in about seven days and reach their full growth in about forty-four days. 

 They pupate within their larval tunnels, and the pupal period lasts about 

 nine days. The moths emerge about the middle of July and deposit eggs 

 for the second generation. A maximum number of 903 eggs was deposited 

 by a single first generation female in life-history cages, with an average 

 number per female of 545 eggs. The second generation larvae hatch in 

 about six days and are nearly full grown by winter. 



Four species of dipterous parasites were bred from the larvae of the 

 European corn borer, and two species of hjinenopterous parasites were 

 bred from the pupae. No parasites were bred from the egg. The per- 

 centage of parasitism by any of these species is very small, and at the 

 present time they cannot be reUed upon to hold the pest in check. 



Burning the plants containing the overwintering larvae, any time 

 during the period from the middle of October to the middle of the next 

 May, is the most effective control method now known. Other methods, 

 applicable under certain conditions, for destroj'ing infested plants are 

 placing in manure or compost; in a silo; burying deeply in the soil; or 

 feeding directly to live stock, preferably shredded or chopped finely. 

 Spraying infested corn plants with arsenicals in order to kill the young 

 larvae feeding on the surface of the plant was not found to be practical, 

 owing to the number of sprayings necessary to keep the growing plant 

 covered with the arsenical, and to the fact that the small per cent of 

 larvae not killed by the arsenical was sufficient to generally ruin the ears 

 of corn for commercial purposes. Cultural practices may aid in avoiding 

 damage by timing the planting of corn in such a manner that the plants 

 may not be at a stage of growth which attracts the female moths during 

 their period of oviposition. The female moths prefer to deposit their 

 eggs upon some plant bearing a soft green seed head. If corn plants 

 bearing a tassel are not available the females habitually deposit their 

 eggs upon some other kind of host plant. 



