Evaluation of Canola Lines for Resistance to Sclerotinia sclerotiorum and Response to Fungicide Application at Langdon, 2003.
Eight cultivars/experimental canola lines were evaluated for their response to fungicide application for control of Sclerotinia sclerotiorum (Lib.) de Bary) (white mold). Significant differences among canola lines were measured in yield, test weight, and percentage oil. A fungicide application showed significant differences in sclerotinia incidence and yield. No differences in line*fungicide interaction were determined.
A study was conducted to determine if different tolerances exist among canola lines for control of white mold and the effects of one Ronilan fungicide application.
This study was designed as a randomized complete block arranged as split plot, sprayed and unsprayed, with four replicates. Plots, 7 x 20 ft. long with 9 rows seeded, were planted on 13 May. The interior seven rows were spaced 6 inches apart and all data was collected from these rows. A space of 12 inches between the outer rows provided an area, to minimize drift to adjacent plots, where no data collection occurred. Sclerotia, about 150 grams per plot were hand broadcast in fall of 2002 over a site that was fallowed in 2002 and lightly tilled to cover the sclerotia. The sclerotia were conditioned to improve chance of carpogenic germination so white mold infection would be more likely to occur in 2003. A second application of conditioned sclerotia was hand broadcast before planting in spring 2003. Additionally ascospores were sprayed at flowering to further increase chances of infection. Supplemental water by overhead sprinkler was added to keep the soil surface moist and encourage sclerotia germination and ascospore dispersal. The method proved quite satisfactory. Herbicides and hand weeding were used to minimize competition from weeds. An application of insecticide on 31 May, Capture (bifenthrin) @ 2.6 oz/acre, was necessary to control severe flea beetle pressure. Ronilan fungicide (vinclozolin) was applied at 12 oz. / acre with a CO2 backpack sprayers with XR8002 nozzles oriented vertically in 18.4 gpa water at 40 psi at on 5 July. Meteorological conditions were air temperature 65� F, relative humidity of 73 %, wind direction NNE with light winds. Some lodging from previous applications of water was still present and was evenly distributed across all plots. The ascospores were sprayed with the same backpack sprayer with XR8001 nozzles in 9.2 gpa water on 11 July. Precipitation, 0.1 inches, was recorded shortly after ascospore application. Sclerotinia incidence was recorded on 14 August by counting the entire second row from the north. side of each plot. Infected plants received a 0 = no lesion present, 0.5 = lesions present on at least on branch, or 1= lesion girdling main stem. The study was harvested on 22 August. Data was analyzed with the general linear model (GLM) in SAS. Least significant differences (LSD) were used to compare means at the 5% probability level.
Table 1. Canola line evaluation
with and without fungicide application for control of Sclerotinia sclerotiorum
Stands were not significantly different but were less than intended due to deep seeding, > 1 inch. Growing conditions were excellent and by 20 %flowering growth stage the plots were entirely covered with canola vegetation. White mold levels ranged from moderate on treated plots to severe on untreated plots. Significant differences were measured among lines in test weight, percent oil, and yield among canola lines. Significant differences were determined in sclerotinia incidence between fungicide applications resulting in a significantly greater yield when fungicide was applied. A reduction in sclerotinia incidence from 19.3 to 10.1 was measured by the application of fungicide which increased yield by an average of 253 lbs. A line*fungicide interaction was not determined. The lack of significant interaction may have been due in part to a presence at low levels of blackleg in some plots. Actual infestation numbers were not recorded An improvement in design by increasing replicate numbers may show significant line*fungicide differences in another production season. As fungicide application only reduced the rating from 19.3 to 10.1 a second fungicide application may further reduce disease and increase yield when disease infestations are severe.