PROJECT RESULTS

Identify Alternate Disease Control Methods for Sunflower Crop Diseases

Mel Reimer

National Sunflower Association of Canada

Morden, Manitoba  R6M 1A4  Canada

Table of Contents:

• Trial 1 - Seed Treatment With Fungicides for Control of Basal-Stalk Rot/Wilt
• Trial 2 - Folicur Application of Fungicides for Control of Head Rot
• Trial 3 - Epidemiology of Sclerotinia Head Rot in Sunflower

ARDI Project:

Total Approved:

Date Approved:

Project Status:

#98-133

$47,100

November 16, 1998

Completed March, 2004

DISCLAIMER:  The research outlined in this project is experimental only.  Products listed in this project are not registered for sunflower use in Canada.

A 4-year field study (2000-03) was conducted to identify seed treatments to control early infections by Sclerotinia sclerotiorum (sclerotinia wild) in sunflowers.  The study demonstrated the efficacy of the following fungicides:  Ronilan, Maxim, Lance (BASF 510), Topsin, and Quadris.  Ronilan and Maxim maintained the emergence and survival of sunflowers at 70-80% and the yield at 90-100% of the health control plots at low Sclerotinia inoculum pressure.  Lance, Topsin and Quadris were moderately effective.  The efficacy of these fungicides dropped under moderate to sever Sclerotinia inoculum pressure in the soil.

A 3-year field study (2001-03) was conducted to identify effective foliar fungicides to control Sclerotinia head rot in sunflowers.  The level of head rot was high enough only in 2002 to show significant differences between treatments.  Benlate, Ronilan and Lance (BASF 510) significantly reduced the head rot by 33-44% and improved yield by 40-50% in 2002.  Quadris and Fluazinam were moderately effective.  Single applications at flowering or 2-wks after flowering were less effective than two applications for each of the fungicides.  These fungicides had similar efficacy trends in 2001 and 2003 in spite of the low levels of head rot infections, but had no significant improvement in yield due perhaps to the low impact of the disease in the trials.  Results based on one good year are not conclusive and further studies are needed before any recommendations to given to sunflower growers.

Field epidemiological studies were conducted (1999 to 2003) to identify the peak head rot infection period in sunflowers using artificial inoculations at weekly intervals with different types of inoculum.  The peak infection period took place between the 1st and 4th week after the beginning of flowering with some variations within the 4-wk period in different years.  The level of infections declined sharply four weeks after flowering.  Ground sclerotinia-infected millet seed was the most effective source of inoculum followed by ascospores, and fresh mycelia.  This information is essential in searching for resistant genotypes, and will help growers on the proper timing of fungicide applications to protect the crop from head rot infections, and improve yield and quality of seed.

The following results were obtained from the 2003 trials. 

Trial #1 - Seed Treatment With Fungicides for the Control of Basal-Stalk Rot/Wilt

Procedure and Project Activities:

• 2002 was the last year of testing.

• Two sunflower hybrids, CLOL 110 (confectionery), and CLOL 803 (oil), were seeded on May 22, and harvested on September 25, 2002.

• Seed treatments with Topsin 5 g/kg, Ronilan 3g/kg and Quadris 5 ml/kg, and a combination Topsin 5g/Captan 2g/Apron 2.5g/kg, Maxim 1g/kg, Maxim/Apron lg&2.5g/kg.  Gavel (Zoxamide) 5 g/kg, and a BASF Exp. fungicide (BASF#1) were used.

• Sclerotinia sclerotiorum inoculum was applied at three concentrations with each seed treatment (lx=5g, 2x=10g, and 3x=15g) in the furrow at the time of seeding.  Inoculum was produced in the laboratory and consisted of a 4:1 ratio of infected millet seed: sclerotia.

• Split plot design was used with 4 replicates, hybrids were main plots and fungicide treatments were sub-plots.  Plots were 2-rows, 0.75 m apart and 3 m long. 30 seed were seeded per row.

• Data was collected on emergence and Sclerotinia infected plants at seedling and at flowering.

• The two rows were harvested for seed yield, and for measuring kernel weight and density.

Results:

The results from the three years of this study 2000-2002 were similar with minor variations between years.  Ronilan and Maxim were effective seed treatments in maintaining the emergence and survival of sunflower at 70-80% at low sclerotinia inoculum pressure in the field, and maintained the yield at 90-100% of the healthy control plots.  However at high sclerotinia inoculum pressure the efficacy of these fungicides dropped to (40-50% survival) and the yield down to 70-90% of healthy control plots.  The BASF 510 (Lance) seed treatments maintained the emergence and survival at 40% and 20% at low and high sclerotinia inoculum pressure and maintained the yield at 80% and 50% of the healthy control. Topsin and Quadris seed treatments were less effective than the above mentioned fungicides.  Gavel seed treatment was not effective in protecting the seed/seedlings from Sclerotinia infections.

These results demonstrated that the order of effective seed treatments among the fungicides used in this trial is in descending order:  Ronilan, Maxim, BASF 510 (Lance), Topsin, and Quadris.

Trial #2 - Foliar Application of Fungicides for the Control of Head Rot

Procedure and Project Activities:

• The oil sunflower hybrid Hysun 311 was seeded on May 15, and harvested on October 1, 2003.

• Sclerotia collected from 2001 seed cleaning were incorporated in the top 2cm of soil between sunflower rows at the bud stage, and irrigated weekly for 4 weeks to enhance ascospore production and head infections.  All plots were artificially inoculated with ground infected-millet seed and ascospores to help develop infections and epidemics.

• Fungicides used were:  Topsin, Ronilan, Rovral, Maxim, Fluazinam, Benlate, BASF 510, CLOL product AG1005, Quadris, and Actigard (enhancement for the plant defense).

• Each compound was used in three treatments:  single application at flowering (August 5), single application at end of flowering, (August 18), and one application at flowering followed by a second application at end of flowering.  Ronilan was used alone and in combination with an Adjuvant (AG 1005 from Croplan Genetics).  Additional treatment of three applications of Ronilan (early, late and very late) was used for comparison.

• Split plot design was used with 4 replicates, hybrids were main plots and fungicides were sub-plots.  Plots were 3-rows, 0.75 m apart and 5 m long.  30 seeds were seeded per row.

• Data was collected on the number of sunflower heads infected in each plot.

• The middle row was harvested for seed yield, assessing the presence of sclerotia in seed samples, and measuring kernel weight and kernel density.

Results:

The artificial inoculation with ground infected-millet seed and ascospores resulted in low levels of head rot infections, 6.7% in the non-created control and the highest infection of 11% (Table 1).  These levels were very low in comparison with data from 2003. One early application of BASF 510, Benlate, Fluazinam, Quadris, and Ronilan reduced the head rot by 63-85% in comparison to the non-treated control.  Such treatments improved the yield, but the only significant increase in yield (34% of the control) was from the two applications of Quadris in 2003.  Two application of Topsin increased the yield by 25% in spite of the minor effect in reducing head rot infections.  In 2003, there were no significant effects of any fungicide treatment on head rot disease index, percent sclerotia in seed, oil content or kernel density, perhaps due to the low levels of head rot in the trial.

The 2003 results were not as conclusive as the results from 2002. The level of sclerotinia head rot in the untreated control was very low in spite of the artificial inoculation using ascospores and ground sclerotinia-infected millet seed. The above normal temperatures and below normal precipitation in August and September of 2003 in the Morden Area created unfavorable conditions for sunflower head rot infections and disease development.  However these results showed a similar trend to the 2002 results (Table 1).

No recommendation can be put forward from this trial based on the 2003 (one good year out of three).

The plan for 2004 is to repeat this trial using a recently purchased misting system at the Morden Research Station.

Table 1.  2003 Sunflower Head Rot Fungicide Control Test – Morden