Monitoring and Control of Puccinia striiformis f. sp. tritici in Wheat Fields Under Rainfed Conditions

The current study was carried out to monitor the date of primary inoculum arrival of P. striiformis f. sp. tritici (Pst) to wheat fields in Sulaimani city and the subsequent development of yellow rust disease during two successive seasons. Results obtained revealed that the first inoculum of Pst arrived in Bakrajo wheat fields in March 2022 and 2023. However, the first yellow rust infection on the susceptible wheat cultivar ‘Hsad’ was observed on April 15 in the first year and April 10 in the second year. The number of uredospores gradually increased with the disease progress, reaching its peak at 51.3 spores/cm² on May 7, 2022, and 187.3 spores/cm² on May 9, 2023. However, uredospores number decreased by the end of the first week of June. Uredospores number per square centimetre was higher in 2023 compared to 2022. Yellow rust control was conducted by using two susceptible wheat cultivars,”Hsad” and “Tamuz-2”, and two different fungicides, Amistar Xtra and Plant Growth Cleaner (PGC), applied at two different times. Results showed that Amistar Xtra treatment significantly reduced the mean coefficient of yellow rust infection in both wheat cultivars. “Hsad” x Amistar Xtra treatment resulted in 83.2 and 85.1% reduction of yellow rust severity for both applications, respectively, whereas “Tamuz-2” x Amistar Xtra treatment resulted in 42.5 and 45.9% reductions for the first and second applications, respectively. PGC treatment had varying effects on the mean coefficient of infection in both susceptible wheat cultivars. The first application of Amistar Extra resulted in changing the infection type from S to MR in “Tamuz-2”, whereas the second application of Amistar Extra changed the infection type to R in Tamuz-2. Both Amistar Extra applications changed the infection type of “Hsad” to R-MR. Application of Amistar Extra significantly increased yield and yield components values in both cultivars suggesting its ability to efficiently control the disease and enhance plant characteristics. Keywords: Fungal diseases, yellow rust, fungicides, disease resistance, plant growth cleaner, Iraq.