Developing Resistance or Tolerance to Insect Attack

Abstract

There are many peculiarities in relation to insect attacks which have not been explained. Some are undoubtedly physiological, others may have a distinct relation to the vigor or condition of the plant, as in the case of the Hessian fly, Phytophaga destructor Say, the lace bugs of rhododendrons and azaleas, Stephanitis rhododendri Horv. and Stephanitis pyrioides Scott, respectively. Injury is also somewhat proportionate to the size and vigor of the host, as evidenced by European corn borer, Pyrausta nubilalis Hubn., infestations. Extended injuries by the elm leaf beetle, Galerucella xanthomelaena Schrank, are dependent in considerable measure upon favorable climatic conditions, these latter undoubtedly resulting in a less vigorous growth. A peculiar and unexplained physiologic-al reaction by gipsy moth larvae, Porthetria dispar Linn., is also mentioned. Evidence available indicates that a number of the cambium borers, namely the bronze birch borer, Agrilus anxius Gory, the two-lined chestnut borer, Agrilus bilineatus Web., the hickory bark beetle, Scolytus quadrispinosus Say, and the cedar bark beetle, Phloeosinus dentatus Say. successfully invade trees with a lowered vitality and that in the case of the first named, it is possible to stimulate growth by feeding and aid trees to actually destroy the borers. It is suggested that a uniform and satisfactory supply of moisture throughout the season and feeding to promote a vigorous growth may be valuable preventive measures in the case of certain insects at least.