The Hibernation Quarters of Laspeyresia Molesta Busck1

Abstract

In 1924, experimental orchard cultivation, supported later by laboratory tests, showed conclusively that thorough cultivation, during the latter part of the month of April, consisting of a plowing to the depth of six inches followed by a disking to the depth of four inches was 100 per cent efficient in the destruction of the larvae and pupae of the Oriental Peach Moth ( Laspeyresia molesta Busck) which had passed the winter upon the ground. The results of further work, in 1925, to determine the relative effectiveness of disking only as compared with plowing only and as compared with these two operations combined, demonstrated the equally high efficiency of a thorough cultivation consisting of disking alone. In 1926 a final study was conducted to determine the relative numbers wintering upon the tree and away from the tree in order to establish the actual extent of the effectiveness of cultivation in the control of this insect. The results of this study indicate the following distribution of the over wintering population under present average conditions in New Jersey—14 per cent in the upper portions of the tree, 11 per cent on the tree trunk and 75 per cent away from the tree—percentages correlated with the adlmdance of mummies and applicable elsewhere subject to variances in infestation and orchard practice. It was also determined that of those larvae overwintering upon the tree trunk 88 per cent constructed hibernacula within the area included in the mound formed when applying paradichlorobenzene for the control of the peach-tree borer, an insecticide also toxic in the case of this insect. These studies, although disclosing the fact that cultivation and the paradichlorobenzene treatment should destroy a high percentage (86%) of the hibernating Oriental Peach Moth, indicate an overwintering population in the upper portions of the tree sufficiently large to constitute a continuance of infestation from year to year in spite of the thorough application of these measures. The knowledge of the relative]y unprotected character and location of these remaining hibernacula suggests the advisability of further work with insecticides of a penetrating nature, with the attendant possibility of placing the control of the insect largely if not wholly within the dormant period.