A sweet orange orchard raised on a heavy soil under ood irrigation, and nanced by the branch, is dying tree by tree. The bark at the collar region just above the union is dark and water-soaked, it ex…

Question

A sweet orange orchard raised on a heavy soil under ood irrigation, and nanced by the branch, is dying tree by tree. The bark at the collar region just above the union is dark and water-soaked, it exudes a brownish gum which dries in akes on the trunk, the bark later splits and peels o to expose the wood, and the a ected tree yellows, sheds its leaves and dies back from the top. The trouble is worst where the irrigation water stands against the trunk and where the trees have been budded low. The eld o cer investigating the loss has to name the pathogen in his note, since the replanting programme he will recommend turns on the choice of a resistant rootstock and on budding high above the ground. The pathogen causing the disease so described in citrus is

Testwala · Accepted Answer

Phytophthora parasitica

Answer: D. Phytophthora parasitica