Location: Sunflower Research
2013 Annual Report
Objective 2. Assess the relative susceptibility of sunflowers to Sclerotinia head rot at R5 (flowering), R6, R7, and R8 growth stages, and whether a hybrid exhibiting resistance or susceptibility to head rot when inoculated at flowering maintains the same disease response when inoculated after flowering. The susceptibility of sunflowers to Sclerotinia head rot at R5, R6, R7, and R8 growth stages will be tested on each of two sunflower hybrids, one that is partially resistant and one that is partially susceptible to head rot when inoculated at R5. Oilseed hybrids sharing nearly identical maturity will be selected. The experiment will be a completely randomized split-split-plot design with four replications; post-inoculation environment (bagged heads or unbagged heads) will be the main factor, sunflower hybrid will be the subplot factor, and inoculation timing will be the sub-subplot factor. The full experiment will be conducted in Carrington and Langdon, ND and a reduced experiment (split-plot design with unbagged heads and no R8 inoculation) will be conducted in Oakes, ND. Sunflower heads will be inoculated with ascospores, and disease development will be facilitated with overhead misting systems.
Objective 3. Establish uniform fungicide trials in three environments to identify the potential of fungicides for managing Sclerotinia head rot of sunflower. Fungicides registered or with anticipated registration on sunflower and fungicides with efficacy against Sclerotinia on other crops will be evaluated for their ability to control Sclerotinia head rot of sunflower. Nine fungicides and a non-treated control will be evaluated at Carrington, ND, Langdon, ND, and Scottsbluff, NE. The experiments will be a randomized complete block design with four replicates. Fungicides will be applied at bloom initiation and again approximately 10 days later. Disease will be promoted by inoculating with ascospores of S. sclerotiorum at flowering and irrigating with microsprinklers (misting systems).