Submitted to: Plant Disease Management Reports
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/22/2013
Publication Date: 3/11/2013
Citation: Chen, X., Evans, C.K., Garner, J.P., Liu, Y. 2013. Evaluation of chemical seed treatments for control of stripe rust in spring wheat, 2012. Plant Disease Management Reports. 7:ST012. Interpretive Summary: Seven fungicide seed treatments were tested for their efficacy in control of stripe rust on spring wheat during the 2012 crop season. The experimental field near Pullman, WA was planted with fungicide treated or non-treated seed of a susceptible winter wheat cultivar, Lemhi, on May 8, 2012. A randomized complete block design experiment with four replications was used including the seven treatments and a non-treated control. Disease severity was assessed from each plot four times during the disease season under the natural infection of stripe rust. Area under the disease progress curve (AUDPC) was calculated for each plot using the four sets of severity data. Relative AUDPC was calculated as percentage of the non-treated control. Grain yield and test weight were measured. Rust severity, relative AUDPC, test weight, and yield data were subjected to analysis of variance and means were compared to determine the difference among the treatments. Stripe rust reached over 90% severity at dough stage. All seed treatments did not reduce rust severity, change test weight, or significantly change grain yield compared to the non-treated control. Some of the treatments even significantly increased rust severity and reduced test weight compared to other treatments. The results showed that the seed treatments do not provide control of stripe rust in spring wheat under the experimental conditions.
Technical Abstract: The study was conducted in a field with Palouse silt loam near Pullman, WA. Fertilizer (Osmocota 14-14-14) was applied at 60 lb/A at the time of cultivation on 8 May 12. A randomized block design was used with four replications for each of the seven treatments and a non-treated control. For each plot, seed of susceptible ‘Lemhi’ spring wheat were planted in rows spaced 14-in. apart at 60 lb/A with a drill planter on 8 May 12. Each plot was 4.4-ft (4 rows) in width and 15.5 - 16.6-ft in length, with spaces of 20 in. between plots. Huskie 15 fl oz plus Axial 80 ml and M-90 140 ml/A were applied on 4 Jun 12 when wheat plants were at early jointing stage. Plant stand was estimated as percentage for each plot at the early tillering stage. Disease severity (percentage of diseased foliage on whole plot) was assessed for each plot on 8 Jun (jointing stage), 10 Jul (flowering), 17 Jul (milk), and 24 Jul (soft dough). Plots were harvested on 15 Sep when kernels had 3-5% kernel moisture, and test weight of kernels was measured. Area under disease progress curve (AUDPC) was calculated for each plot using the five sets of severity data. Relative AUDPC was calculated as percent of the non-treated control. Rust severity, relative AUDPC, test weight, and yield data were subjected to analysis of variance and means were separated by Fisher’s protected LSD test. The weather conditions during the crop season allowed a moderate level of stripe rust epidemic. There were no significant differences in plant stand, indicating that the seed treatment chemicals did not have obvious phytotoxicity. On 8 Jun at flag leaf stage, stripe rust severity was scored as 2-3% rust severity. At 10 Jul (flowering stage), plants of non-treated control had 30-50% rust severity. At 17 Jul (milk) and 24 Jul (soft dough), stripe rust developed to 80-90% and 90-100% severity, respectively. There were some differences in rust severity and relative AUDPC among the treatments, but most treated plots were not significantly different from the non-treated control. None of the treatments significant reduced rust severity and relative AUDPC, but two treatments [Difenocon 18 gai + Ipconazole 1.5 and Dividend Extreme (185 ml/100kg)] had significantly higher rust severity or relative AUDPC than the non-treated control. Similarly, none of the treatments significantly increased grain test weight, but seven of them [Nipsit Inside Insect 5.00 FS 1.000 fl oz/cwt, Rancona pinnacle (325 ml/100kg), Rancona pinnacle (540 ml/100kg), Rancona 3.8 fs (3.4 ml/100kg) + Dividend Extreme (185 ml/100kg), Dividend Extreme (185 ml/100kg), UBI 9292 (325 ml/100kg), and UBI 9349 (65 ml/100kg)] actually reduced test weight significantly compared to the non-treated control. No significant difference was observed among the treatments and non-treated control. The results showed that the tested chemicals did not have any positive effect on control of stripe rust and grain yield under the field disease conditions.