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A Nitrogen Deficiency Disease of Sugarcane Probably Caused by Repeated Pesticide Applications. H. D. Dubey, Associate Soil Microbiologist, Department of Agronomy and Soils, Agricultural Experiment Station, University of Puerto Rico, Río Piedras 00928. Phytopathology 60:485-487. Accepted for publication 14 October 1969. DOI: 10.1094/Phyto-60-485.

Yellowing and drying of leaves, stunted cane growth, and partial to complete death of sugarcane plants, occurring in more or less round patches in the field, surrounded by healthy canes, was observed at one of the Central Aguirre Farms in southern Puerto Rico in February 1968. No pathogenic organisms were found in cane roots or shoots. Soil from the affected area was significantly low in NO3-N, nitrogen mineralization was low, and only Penicillium citrinum was found in this soil, as against a heterogeneous fungal population in soil from the unaffected area. The cane leaves from the affected area were low in N. Growth of test plants in the greenhouse in soils from the affected area was reduced both in sterilized and nonsterilized soils. The problem was remedied by the addition of mineral nitrogen. Repeated applications of pesticides, especially the 19 applications of the fungicides maneb, zineb, and tribasic copper to the preceding tomato crop, probably changed the microbial population so much that mineralization of soil nitrogen was inhibited, resulting in N starvation of the following sugarcane crop.