514 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



NATURE AND AMOUNT OF DAMAGE. 



Present experience with it in this country would seem to indicate 

 that corn is its favorite food plant. Its work on certain garden 

 vegetables and truck crops other than corn has caused no economic 

 losses to such crops, or only trifling losses, and is significant only 

 as indicating that some of these may be the means of spreading the 

 insect. 



In tlie relation of this insect to corn, there are, fortunately, some 

 hopeful features. It develops from the experience of this year that 

 it is double-brooded in Massachusetts and sinoie-brooded in New 

 York, owing to differences in climate. As a smgle-brooded insect 

 in New York, its damage to corn has been negligible as reflected 

 in the crop. In Massachusetts, even with the large numbers result- 

 ing from the second brood, its damage has seldom exceeded 10 per 

 cent of the ears and in most fields in the invaded districts much less 

 than this. Even the injury to such ears has been as a rule not greater 

 than that produced by the ordinary corn ear-worm over large areas 

 of the United States where the latter insect is an important annual 

 pest, often infesting all or nearly all ears of corn. The highest 

 damage in Massachiisetts has. represented about 25 or 30 per cent 

 of tlie ears, and this has been in isolated fields surrounded by Avcedy 

 areas more or less infested with the insect, the corn therefore in a 

 way concentrating the insect from these surrounding sources of 

 supply. The insect is essentially a stem or stalk borer, and appar- 

 ently corn can harbor from one to several of these insects in a stalk 

 Avithout appreciable effect on the development of the ear. In the 

 case of carl}' corn, its infestation of the stalk is very apt to come 

 after the ear is practically ready for harvest, and infestation of the 

 stalk may increase and continue even for a considerable period after 

 harvest. 



From the experience in New York, where the insect has evidently 

 been for about nine 3'oars, it would seem to be fulh' established that 

 as a single-brooded insect it will be a negligible factor in relation to 

 corn production, and this is especially emphasized by the fact that 

 the crop of the New York district is almost altogether of the small 

 flint corn which in New England has been notably susceptible to 

 damage. 



In climates where the insect has two broods, as in New Eng- 

 land, and perhaps as in the South, the possibilities of damage 

 are much greater. With respect to these possibilities, however, it 

 should be noted that the few patches of large-stalked vigorous field 

 corn such as characterizes the great corn belt of the United States, 

 grown in the invaded areas in Massachusetts as a part of the depart- 

 ment's experiments and by farmers, have shown an almost complete 

 immunity from serious infestation by this insect. It remains to ba 

 determined, therefore, whether this insect will actually develop into 

 a real menace to the great corn crop of the United States. That 

 much harm can be done by this insect where it is double-brooded, as 

 in New England, to sweet corn and to such dwarf corn as the flint 

 varieties common!}' cropped in the upper limits of the corn belt of 

 the United States, seems to be demonstrated. In regions where such 

 corn is grown, however, the insect vrill undoubiedly be generally 

 single-brooded. Immediately about Boston the climate is apparently 

 made more favorable to the insect by ocean currents. 



