EFFECT OF INSECTICIDES AND HERBICIDES APPLIED TO SOIL ON THE DEVELOPMENT OF PLANT DISEASES. I. THE SEEDLING DISEASE OF BARLEY CAUSED BY <i>HELMINTHOSPORIUM SATIVUM</i> P. K. &amp; B.

Abstract

From the results obtained when nine insecticides and ten herbicides were applied at a series of dosages to soil infested to various degrees with Helminthosporium sativum P.K. &amp; B. it was found possible to separate these chemicals into four groups on the basis of their effects on the growth of barley seedlings and on the development of rootrot infection. Group A (schradan, isodrin, DCU, IPX, and TCA) affected neither host nor disease development. Group B (lindane, dieldrin, and DDT) stimulated the growth of barley seedlings without affecting disease development. Group C (maleic hydrazide and heptachlor) stimulated seedling growth but increased the severity of infection. Group D (aldrin, endrin, chlordane, NPA, 2,4-D, monuron, DNBP, and dalapon) did not affect the growth of seedlings but reduced rootrot infection. Only DNBP was toxic to H. sativum in culture.