Microdochium Patch and Dollar Spot Management
Microdochium Patch (Microdochium Nivale) can be a tough problem on turf throughout the cooler months of the year. This disease is also known as Winter Fusarium in older references. Microdochium patch develops in cool to warm, wet weather.
Microdochium Patch (Winter Fusarium)
What To Look For
Symptoms start off as small, water-soaked spots on turf that expand and turn gray or tan with a red-brown or dark, greasy-appearing margin. Fluffy, white Mycelia can be observed at the edge of the patches, and often, dead tissue is covered by pink spore masses.
Wet conditions during maximum daytime temperatures of 7-20°C favour this disease, and explosive outbreaks can occur when daytime temperatures are 15-20oC with overcast, foggy or wet weather. It is most common on cool-season turf, especially Winter Grass, but can occur on warm-season turf such as Couchgrass and Kikuyu. This disease is favoured in shaded or poorly-drained locations and excessive nitrogen fertility conditions.
The Solution
Rotate fungicide classes when multiple applications are used in the season for Microdochium Patch control to prevent resistance development. Addition of a multi-site fungicide when making curative applications will also help minimize resistance development.
Severe Microdochium symptoms, water-soaked spots that turn gray or tan with a red-brown or dark, greasy-appearing margin. Fluffy, white Mycelia can be observed at the edge of the patch.
Dedicate® Forte® in curative trials has demonstrated excellent curative activity of Microdochium patch with long residual, good turf safety and the added benefits of Stressgard technology.
Dollar Spot
The Problem
Dollar Spot, caused by Clarireedia spp., is a widespread and very destructive turfgrass disease that can be observed throughout the year. Dollar Spot is known to attack most cool and warm season turfgrass species, including Winter Grass, Bentgrass, Fescue, Kentucky Bluegrass, Perennial Ryegrass, Couch Grass, Zoysia and Buffalo.
What To Look For
Dollar Spot is favoured by air temperatures ranging from 16-32°C (optimum 21-27°C), with extended periods of high humidity (>85% at night). The disease tends to be most severe with warm days, cool nights, infrequent rain but long dew periods, daily ground fogs that extend leaf wetness periods, and low nitrogen fertility.
Dry weather and extended periods of high temperature above 35°C may shut down summer epidemics of dollar spot. However, autumn outbreaks are common due to either a return to disease-conducive temperatures, increases in moisture or rainfall, or a reduction in cool-season turfgrass vigour.
Symptoms of dollar spot can vary based on the turfgrass species and height of cut. Under close mowing heights, as with intensively-maintained Bentgrass or Winter Grass, the disease appears as small circular straw-coloured spots of blighted turf 2-5 cm in size. On coarser-textured turf maintained under higher mowing practices, the blighted areas can be larger, straw-coloured patches 2-15 cm in diameter. Affected patches frequently coalesce and involve large areas of turf.
Distinct hourglass-shaped lesions often develop on infected leaves. On short-mowed turf, whole leaves may become blighted without distinct lesions.
When the fungus is active and leaf surfaces remain wet, a fine, white, cobwebby Mycelium covers the infection centres or diseased patches during early morning hours.
The Solution
Implementing proper cultural practices is crucial to reducing disease severity. Management tactics include maintaining adequate nitrogen, especially with spoon-feeding during the summer on low mowed cool-season turf; removing dew; avoiding drought stress; alleviating compaction and thatch; and maximizing air movement.
Fungicides are a key part of an integrated Dollar Spot management program. Since dollar spot is a foliar disease, select spray nozzles and volumes that provide good coverage to maximize fungicide activity. Early spring applications of fungicides can significantly delay the onset of Dollar Spot epidemics. DMI fungicides timed for fairy ring and patch disease control (average soil temperatures of 13°C at a 5-10-cm depth) can provide early season Dollar Spot control. Routine fungicide applications are commonly needed through the summer when air temperatures are 21-32°C and should be continued into the autumn for Dollar Spot control.
Resistance to certain classes of fungicides can be significant for Dollar Spot. Resistance to the benzimidazole fungicides is common.
Resistance to SDHI fungicides is suspected but not officially validated yet, but it is critical to avoid overuse of this expanding group of fungicides to limit the chances of resistance developing. Preventive applications and rotating fungicide classes, including the use of multi-site fungicides, is important for reducing the risk and impact of resistance.
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