THE EUROPEAN CORN BORER AND ITS CONTROL. 65 



SUMMARY. 



The European corn borer has recently become established in the eastern 

 part of Massachusetts. This pest has long been recorded in Europe and 

 Asia as one of the most serious insect enemies of corn, hemp, millet, hops 

 and other crops. It was probably introduced into Massachusetts through 

 the importation from Europe of raw hemp for use in cordage factories, 

 about the year 1910. 



The insect was first discovered in Massachusetts in the summer of 

 1917. At that time it was causing severe damage to sweet corn and 

 other plants. Preliminary investigations indicated that the insect had 

 become established over an area of about 100 square miles immediately 

 north and northeast of the city of Boston, and that the serious nature of 

 the pest called for prompt and vigorous action by both State and Federal 

 authorities if the corn crop of the country was to be safeguarded. 



During the season of 1918 the Massachusetts Agricultural Experiment 

 Station and the United States Bureau of Entomology co-operated in a 

 further investigation of the insect, in order to obtain detailed information 

 concerning its distribution, habits and food plants, with a view to insti- 

 tuting quarantine and control measures that would confine the pest to its 

 present area and lead to its ultimate control. 



As a result of these investigations it was determined that up to Novem- 

 ber, 1918, the European corn borer had established itself in an area of 

 about 320 square miles, comprising 34 towois, located immediately west, 

 north and northwest of the city of Boston. 



The insect attacks a great variety of both wild and cultivated plants, 

 including sweet corn, field corn, fodder corn, timothy, oats, celery, to- 

 matoes^ potatoes, beans, beets, Swiss chard, chrysanthemums, dahlias, 

 gladioli and many qf the larger weeds and grasses. 



Corn is its favorite food plant, however, and is injured by the pest to 

 a greater extent than any of its other host plants. All parts of the corn 

 plant are attacked, except the fibrous roots. The economic injury to 

 corn consists of the following: (1) injury to tassel which results in poor 

 fertiUzation; (2) injury to stalk which reduces vitality of plant; (3) 

 injury to stalk which causes breaking over of plant; (4) injury to stalk 

 which indirectly affects the ear by cutting off its supply of nutriment; 

 (5) injury to ear which directly affects the j'ield; (6) injury to the silk of 

 the ear which results in poor fertilization. 



A maximum of 117 full-growii European corn borer larvae have been 

 taken from one corn plant and 311 full-grown larvae were dissected from 

 a single hill of corn containing four plants. The average number of 

 larvae dissected from 75 corn plants, taken at random in the same field, 

 ■was 46. This is at the rate of 1,050,640 larvae per acre of corn. As many 

 as 15 were found attacking a single ear of sweet corn. 



Field counts made in infested corn fields showed that frequently as 

 high as 100 per cent of the ears were infested. 



