Identification and control of major seed potato storage diseases in Benguet and Mountain Province, Philippines

Commonly associated fungi which did not cause rotting when inoculated alone in intact tubers included Aspergillus sp., and Penicillium sp. Streptomyces scabies, although frequently observed, was not considered a storage pathogen since it affects only the skin. In the control of storage rots in 5-month long in-ground storage (IGS) by drenching fungicides on the tubers at maturity, fungicide application did not significantly control Fusarium solani, Pseudomonas solanacearum and disease complex of F. solani + Rhizoctonia solani. Longer IGS increased the incidence of the major storage pathogens as well as losses in yield. The study on the chemical control of F. solani, R. solani and joint infections by F. solani + R. solani was more effectively controlled than R. solani and that joint infection by the two was significantly lower than their separate infections. Fungicides applied as protectant dip were most effective followed by eradicative dip, protective and eradicative sprays. As protectant dip, benomyl effectively controlled F. solani and joint infections by F. solani + R. solani, while thiophanate methyl effectively controlled R. solani. Fungicide application did not effect increased yields of extra-large and small tubers but effected increased yields of large, medium and total marketable tubers. Treatment with mancozeb and treatments with thiophanate methyl and chlorothalonil most significantly enhanced increased large tuber yield and medium tuber yield, respectively. Mancozeb + cymoxanil, benomyl and mancozeb effected increased total marketable tubers most significantly. The use of fungicides to control rotting by F. solani encountered during the breaking of dormancy with calcium carbide showed promising results. Benomyl effectively controlled F. solani during the incubation period for breaking dormancy to one month exposure of sprouted tubers and even latent infection as manifested by the control up to harvest when these tubers were planted. Chlorothalonil, PCNB [pentachloronitrobenzene] and thiophanate methyl likewise provided adequate protection. There was no inhibition of germination in addition to increased yield.