ISHS Acta Horticulturae 570: VIII International Symposium on Flowerbulbs
POTENTIAL ALTERNATIVES TO PCNB TO CONTROL THE DEVELOPMENT OF CROWN ROT AND GRAY BULB ROT ON BULBOUS IRIS |
| Author: | G.A. Chastagner |
| Keywords: | trifloxystrobin, flutolanil, azoxystrobin, Sclerotium delphinii, Rhizoctonia tuliparum |
| Abstract:
Soil applications of PCNB (Terraclor) at the time of planting are used to control crown rot (Sclerotium delphinii) and gray bulb rot (Rhizoctonia tuliparum) on approximately 98% of the bulbous iris acreage in the Pacific Northwest. PCNB is typically applied as an in furrow treatment at the rate of 5.0 to 6.7 g a.i./m of row and is the most common fungicide used to control these two soilborne diseases. During the past few years there have been a number of fungicides developed that have the potential to control these diseases. A series of field tests were conducted at WSU-Puyallup to compare the effectiveness of trifloxystrobin (Compass at 0.013 to 0.026 g a.i./m), azoxystrobin (Heritage at 0.026 to 0.104 g a.i./m), fludioxonil (Medallion at 0.0065 to 0.013 g a.i./m), and flutolanil (Contrast at 0.031 to 0.25 g a.i./m) to PCNB at 6.7 g a.i./m in controlling these two diseases. Bulbs were planted into soil that had been artificially infested with inoculum, which resulted in moderate to high disease pressure during the tests. Depending on the rate used, all of the fungicides except fludioxonil significantly reduced the development of crown rot and increased yields compared to the check. Some rates of azoxystrobin, flutolanil, and trifloxystrobin provided control equal to PCNB. Flutolanil and trifloxystrobin were the most effective materials in controlling gray bulb rot. | |
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