24 THE REPORT OF THE No. 36 



In closely piled corn that is left outside all winter, whether it is stooked 

 tightly or shredded and then piled closely, the larvae leave the dense damp 

 centre of the mass and will be found entirely in the outer six to eight inches 

 of the pile. 



Varietal Infestation of Corn. As far as we have determined at present, 

 there does not seem to be any variety more subject than another to the deposition 

 of eggs by Corn Borer moths. During the egg-laying season, comparative counts 

 were kept on various plots of flint, dent and sweet corn and the larval popula- 

 tion of these plots was determined at time of harvest. It was found that the 

 results were somewhat contradictory, but on the average in the first part of 

 oviposition period the sweet corn was free from eggs while the taller flint and 

 dent varieties were freely laid on. By harvest time, the sweet corn was generally 

 more heavily infested than the other varieties. In some cases, however, the 

 flint corn did have more eggs on it than the dent and the larval population was 

 higher. But on an average through the season eggs were laid equally on all 

 varieties. 



Artificial Infestation of Plants other than Corn. The following 

 plants other than corn, were used in garden plots to see if moths would ovi- 

 posit on them under natural conditions and if larvae could mature in them. 

 These plants were grown right amongst the corn plots, under identical conditions. 



Plants used: Zinnia, snap dragon, salvia, mignonette, gladiolus, potato, 

 tomato, cosmos, bachelor's button, barnyard grass, green fox-tail, yellow fox- 

 tail, pigweed, ragweed, lambs quarters. Also two other plants with thick soft 

 stems, commonly grown in gardens, whose names were not recorded. 



On none of these plants did moths lay eggs and to none of them did larvae 

 migrate from infested corn alongside. Therefore they were all covered with 

 wire cages in which moths were liberated in numbers from three pairs (male 

 and female) to 16 pairs at a time. With the exception of cosmos, tomato and 

 tobacco, the caged moths laid eggs freely on all plants, especially on the snap- 

 dragon, pigweed, lambs quarters, dahlia and the grasses, and the larvae flourished 

 and reached maturity, although most of them died in the first instance, as on 

 corn. 



This failure on the part of larvae to arrive at maturity, was especially notice- 

 able on weeds such as pigweed (an apparently ideal host as far as softness and 

 thickness of stem is concerned) and lambs quarters, where out of a total of 224 

 eggs on one large plant of pigweed five larvae reached maturity and out of 744 

 eggs laid on one plant of lambs quarters no larvae reached maturity. The 

 cosmos became infested by larvae which hatched from eggs laid on the sides of 

 the cage, but the potato, tobacco and tomato plants were untouched to the end. 



Field Infestations of Plants other than Corn. Of plants growing 

 among corn or immediately contiguous to cornfields, the following were found 

 at different times in 1921 and 1922, to be infested by corn borer larvae: White 

 sweet clover (only one very slight infestation) golden rod, mullein, Canada 

 thistle, wild sunflower, blueweed, wild raspberry, burdock, yarrow, ground 

 cherry, lady's thumb, pigweed (favorite host) ragweed and tumbling pigweed. 

 The borer was also found in apples on the ground and tomato fruit. It is practi- 

 cally certain that all the above infestations were from migrating larvae only, 

 never by larvae from direct oviposition. It was never found in tomato, tobacco 

 or potato stems, in red clover, beans, pumpkins and garden sunflowers, although 

 these were grown right amongst infested corn. 



In 1922, a heavy infestation was found in oats growing in a field which had 

 contained very heavily infested corn in 1921. This oat infestation was suspected 

 in 1921 as being probable but it was not confirmed until this year, when it was 



