Oakes Irrigation Research Site
Carrington Research Extension Center * North Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Voice: (701) 742-2189, FAX: (701) 742-2700, email: rgreenla@ndsuext.nodak.edu

COMPARISON OF FUNGICIDES AND TIMING OF SPRAYS FORCONTROL OF WHITE MOLD ON IRRIGATED DRY BEANS, 1996

Pat L. Gross and Jim R. Venette

Department of Plant Pathology, NDSU

Result summary

Table 78. Fungicide effects on white mold and edible bean yields

This study was conducted at the Oakes Irrigation Research Station on an Embden loam soil that was heavily infested with sclerotia of Sclerotinia sclerotiorum. Based on soil tests, 140 lb/acre 10-50-0, 156 lb/acre 0-0-60 and 78 lb/acre 21-0-0-24 were applied on April 17 and 50 lbs N/acre as 28-0-0 fertilizer was side dressed on June 20 . Treflan MTF herbicide was applied at 1.0 pt/acre on May 20 and incorporated. Pinto beans were planted on May 20 in four-row plots with rows 30 inches. apart. Each row was 20 ft long and a 2 ft buffer area was included at each end of each row. At planting, soil moisture was adequate and soil temperature was 61F. Dual was applied preemergence at 1.5 pt/acre on May 21. Basagran at 2 pt/acre was sprayed on June 17 and again on July 1. Cultivation and hand-weeding supplemented weed control. Beginning May 29 plots were sprinkler irrigated every 3 to 4 days or as needed. The first fungicide spray was applied at 10% bloom on July 3. Fungicides were suspended in deionized water adjusted to pH 7.0 with NaOH and applied with a CO2-powered sprayer at 35 psi at a rate of 37.5 gal/acre through Teejet 8001 nozzles. The sprayer was equipped with four drop nozzles configured to apply fungicide on each side and over the top of each of the rows. Benlate 50W and water-sprayed plots were included for comparisons. The experimental design was a randomized complete block with four replicates. White mold incidence and severity were evaluated July 25 and August 1. Incidence was evaluated as disease presence or absence at 22 sites within randomly selected 10 ft segments of the center two rows of each plot. Severity was estimated at five random locations within each of the center two rows. At each location, the plant material in a 1 ft segment of row was rated on a 0 to 5 scale: 0=0%, 1=1-10%, 2=11-25%, 3=26-50%, 4=51-85%, and 5=86-100% infection. Plants were harvested August 23 from 10 ft sections of the center two rows of each plot. Plants were clipped from their roots, collected in burlap bags, dried at 120 F for 5 days and threshed with a belt thresher. Seed samples were cleaned by aspiration and hand-picking. Seed moisture was uniformly near 8%, so yields were calculated from nonadjusted weights.

RESULTS

Bean growth was excellent and the canopy was completely closed by July 15. First bloom was apparent on July 2. Plant wetness was maintained by dew, rain and irrigations. White mold was found in the field on July 19. Plots near the shelter belt side of the field tended to have more white mold. Treating plants with Topsin on July 3 and 8 significantly reduced white mold incidence and severity compared to one application of Topsin of July 3. Plants treated with Topsin of July 3 and July 8 had significantly higher yield compared to the untreated control or one application of Topsin.

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Table 78. Fungicide effects on white mold and edible bean yields.
Treatment Rate Disease rating Yield1
incidence severity
July 25 August 1 July 25 August 1
per acre ------------------------- % ----------------------- cwt/acre
Untreated control 50.6 67.0 9.0 44.5 15.1
Fluazinam 500F 0.8 pt 27.3 65.9 4.8 28.1 17.5
IB11924 2.0 pt 44.3 76.1 13.3 38.9 16.6
Topsin M 70WP 1.5 lb2 50.0 77.2 24.9 56.4 15.1
Topsin M 70WP 1.5 lb3 30.7 54.5 7.3 28.6 20.0
Topsin M 70WP 1.5 lb4 44.3 65.9 13.5 29.3 18.1
Benlate 50W 1.5 lb 33.0 40.9 3.9 15.5 18.1
RH-141647 3.0 lb 50.0 65.9 19.0 42.0 16.7
LSD (P=0.05) 14.0 13.7 10.0 19.0 3.6

1Yield is calculated from cleaned beans taken from 0.0011478 acres and weighed at 8.0% moisture.
2 Topsin applied once at 10% bloom on July 3.
3 Topsin applied twice, July 3 and July 8.
4 Topsin applied twice, July 3 and July 11.

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