Talking Turf

  • May11Thu

    Getting to the Root of the Problem

    Taking Control of Summer Patch May 11, 2017 Dr. Paul Giordano
    The summer of 2016 presented unique challenges for superintendents growing Poa annua in most of Eastern Canada. Drought conditions throughout June and July resulted in stressed turf which was subsequently prone to opportunistic disease infestations. By late August, summer patch symptoms became vividly apparent, and curative treatments did not fare well in alleviating damage to putting surfaces.

    The Problem:
    Summer patch, caused by the pathogen Magnaporthe poae, is a crown and stem disease of annual bluegrass and Kentucky bluegrass that occurs during warm and hot weather conditions. In Canada, symptoms typically appear in mid-late summer, although the pathogen begins infecting turf root tissue much earlier in the spring months. Damage from summer patch can range from small (10-15 cm) to large (20-30 cm) irregularly-shaped or circular yellow-to-bronze coloured patches. Symptoms progress rapidly when turf is stressed from drought, compaction, or mechanical traffic, leaving voids of dead or dormant areas in the turf that can severely disrupt playability. Microscopic signs of the pathogen on turfgrass roots include darkened tissue with characteristic ectotrophic “runner” hyphae that are present on both the external and internal components of the root cortex.

    Field symptoms of summer patch on a mixed stand of annual bluegrass, Kentucky bluegrass and creeping bentgrass (left). Fungal signs of ectotrophic runner hyphae on affected Poa annua roots when viewed under a compound microscope (right). Photos by Dr. Paul Giordano, Bayer.

    The Solution:
    As with most of the patch diseases on turf, summer patch should be managed through a series of cultural and chemical practices that limit turf stress and encourage root growth and health throughout the season. Adequate nitrogen fertility throughout the summer months has shown to significantly reduce summer patch severity. Improving soil drainage and compaction issues can help to mitigate summer patch severity and alleviate underlying issues that contribute to plant stress and disease development.

    2016 highlighted areas on golf courses that were predisposed or prone to summer patch outbreaks. Preventive fungicide programs should start when average soil temperatures at a 5 cm depth are around 65-68 F (18-20 C). In areas with a history of summer patch incidence, these applications should be repeated monthly through late summer in order to maintain adequate control of the disease during stressful periods. Systemic DMI and QoI fungicides have shown the best efficacy against summer patch and can be combined with anthracnose programs for a more complete annual bluegrass disease management strategy.

    Luckily for us in Canada, a new tool is available that will change the game for summer patch management. Mirage Stressgard has been shown to be one of the most effective DMI fungicides for summer patch control (see below), and is also extremely active against anthracnose. Stressgard Formulation Technology products help to reduce environmental and abiotic stresses that promote opportunistic diseases like summer patch. Applications of Mirage Stressgard should start when mid-day soil temperatures reach 18-20 C consistently for 3-5 days. For best results, fungicide applications should be made in high water volumes (8-12 L/100 sq M) or drenched in via irrigation immediately after spraying in order to target the product to the root zone.

    Implementing proper cultural practices and solutions like Mirage Stressgard can protect your turf from the unpredictable summer stresses that lie ahead. For more information on Summer Patch and other Bayer Solutions, visit our Solutions Guide, or contact a Bayer turf specialist.