Fall Disease Prevention and Control

By Rob Golembiewski, Ph.D.

Although fall has just begun, it is not too early to start thinking about rejuvenating lawns and getting them ready for winter. Unfortunately, turf pests may cause a decline in lawn quality (both aesthetically and functionally). The degree of turf deterioration is a function of the grass species, type of pest, and the environmental conditions before, during and following the pest involvement.

Pests are part of any ecosystem, and managing turfgrasses to optimize their competitiveness is the essence of any pest management program. Rather than rely on a particular pesticide for control, successful pest management must include the integration of proper cultural practices. Without optimum cultural practices, any pesticide solution to a pest problem will not be as effective as it could be, and is unlikely to be permanently successful.

Disease control

Disease can be defined as a continual disturbance of normal plant function by a pathogenic agent or environmental factor. Non-infectious diseases cannot spread between plants, and are caused by non-living agents such as drought, soil compaction, chemical burn or nutrient deficiency. Infectious diseases are caused by pathogenic agents (fungi, bacteria, viruses, nematodes) and are passed from plant to plant. Most turfgrass diseases are caused by fungi.

The development of an infectious disease requires three things: susceptible host grass plant; presence of the pathogen; and a favorable environment. The relationship between these components is called the disease triangle and control tactics are aimed at eliminating one of the components. Methods of disease control include resistant varieties, cultural practices, biological control, and chemical control. Numerous diseases can occur on lawns with some of the more common diseases outlined as follows:

Fairy Ring

Grasses affected: All turfgrasses, especially Kentucky bluegrass
Season: April-November
Symptoms and signs: Rings of dark green; sometimes rings with dead zones, with or without tan mushrooms
Conditions favoring disease: Fungus thrives in warm and wet weather, but injurious effects not noticeable until hot and dry weather
Cultural control: Aerify, maintain adequate soil moisture, use wetting agents, fertilize to mask rings

Gray Snow Mold

Grasses affected: Annual bluegrass, perennial ryegrass, Kentucky bluegrass
Season: October-April
Symptoms and signs: Irregular, dead, bleached areas with gray mold
Conditions favoring disease: Air temperatures 32 to 36 degrees Fahrenheit with deep snow falling on unfrozen ground, snow cover 40 to 60 days (mild disease), 60 to 90 days (moderate), greater than 90 days (severe)
Cultural control: Avoid late fall fertilization that leads to lush growth, control excessive thatch, remove tree leaves from turf, control drifting snow, promote rapid drying in early spring by removing snow or improving drainage

Helminthosporium Leaf Spot and Melting Out

Grasses affected: All turfgrasses, especially Kentucky bluegrass and fine fescues
Season: All year, particularly spring
Symptoms and signs: Tan to purple spots on leaves with eventual yellowing and thinning of turf
Conditions favoring disease: Spring and fall, temperatures 55 to 70 degrees Fahrenheit, with extended periods of rainfall and/or overcast weather
Cultural control: Raise mowing height, mow frequently to avoid stressing turf, avoid excessive nitrogen and thatch, irrigate sparingly during the day only when needed

Microdochium Patch/Pink Snow Mold

Grasses affected: Annual bluegrass, perennial ryegrass, Kentucky bluegrass
Season: Late fall and early spring (Microdochium patch), under snow cover (pink snow mold)
Symptoms and signs: Browning and thinning of turf in large indefinite spots
Conditions favoring disease: Heavily thatched turf that is growing slowly, prolonged rainfall and air temperatures 35 to 60 degrees Fahrenheit, poor drainage, optimal is high humidity and air temperatures 32 to 45 degrees Fahrenheit, snow cover ideal for development
Cultural control: Maintain low soil pH (below 6.5) and balanced soil fertility, avoid nitrogen fertilization after turf hardened off, control excessive thatch, remove morning dew, improve air movement, provide surface drainage

All photos courtesy of Bayer CropScience LP

Necrotic Ring Spot

Grasses affected: Kentucky bluegrass
Season: March-May and September-November
Symptoms and signs: Dead circles, arches, and patches with centers generally colonized by weeds or other grasses
Conditions favoring disease: Fungus thrives in cool wet weather in spring/fall, injurious effects may not appear until high temperatures and/or drought stress
Cultural control: Prevent drought stress during summer with light daily irrigation, fertilize with organic fertilizers, raise mowing height, control thatch buildup

Red Thread

Grasses affected: Perennial ryegrass, fine fescues, tall fescue, Kentucky bluegrass
Season: February-November
Symptoms and signs: Bleached or tan-colored irregular areas with red fungal strands


 Conditions favoring disease: Day-night temperatures 45 to 65 degrees Fahrenheit, prolonged periods of rainfall, heavy dew conditions, slow growing turf
Cultural control: Increase nitrogen fertilization, increase air circulation, avoid drought stress


Grasses affected: Perennial ryegrass and Kentucky bluegrass
Season: April-October
Symptoms and signs: Leaves turn yellow; yellow to orange to reddish-brown powdery growths on leaves
Conditions favoring disease: Overcast or cloudy weather, air temperatures in the low 70s, high humidity brought on by fog or light rain showers
Cultural control: Stimulate growth via water and/or fertilizer

Although many of these diseases can be quite dramatic looking, very few cause serious enough damage to lawns to warrant a fungicide application. However, if a fungicide application is needed, make sure to accurately identify the disease and select an appropriate systemic fungicide. To reduce or eliminate the need for fungicides, implement an integrated turf management program emphasizing sound cultural practices. Lastly, when a disease issue arises, take the following steps to accurately diagnose the problem before implementing any control strategies.

Gain perspective of the distribution of the problem in the turfgrass stand.
Identify which grass specie(s) is/are being affected.
Determine the turf plant part being affected (foliage, crown, root).
Identify the type of signs and/or symptoms being observed.
– Sign: Pathogen or its parts or products seen on the host plant (e.g. rust on turf)
– Symptom: External or internal reactions or alterations of the plant as a result of disease (e.g. chlorosis or discoloration of the turf)
Review the history of the site.
– Weather: Wet, dry, warm, cool, sunny, etc.
– Chemical: Fertilizer or pesticide applications
– Stand Condition: Soil, thatch, pH, turf species or cultivar
– Cultural practices that may have stressed turf
If unsure, send a sample to a turf/plant diagnostic laboratory.

Dr. Rob Golembiewski is a greens solutions specialist for the Environmental Science Division of Bayer CropScience LP with the responsibility of providing technical support for the Midwest Turf & Ornamental Market. Most recently, he served as the Turfgrass Specialist at Oregon State University. Rob received his B.S and M.S. from Michigan State University and his Ph.D. from The Ohio State University. His career has included positions with Montana State University, Dow AgroSciences, Paramount Landscape, and the University of Minnesota, Crookston. 

Bayer CropScience is committed to bringing new technology and solutions for agriculture and non-agricultural uses. For questions concerning the availability and use of products, contact a local Bayer CropScience representative, or visit Bayer CropScience online at www.bayercropscience.us

Trees and Ornamentals

By Stephanie Darnell

As you know, healthy ornamentals do more than just improve the appearance of landscapes. They can help maintain temperature control, block out traffic sights and sounds, and may add to a homeowner’s property value. Though protecting ornamentals requires broad expertise, time, and labor-intensive work, keeping these plants healthy and vibrant ultimately can help you maintain, and even grow, your loyal, satisfied customer base.

De-stress with moisture

After this year’s hot, dry summer, trees and shrubs throughout the nation have suffered from a lack of moisture. As a result, many plants are stressed going in to the fall season. Plants under stress have a difficult time fending off insects and diseases, which is why it is important to protect trees and shrubs this fall from pests that may impact their ability to thrive through the winter and reemerge healthy in spring.

To help trees and shrubs build their defenses, be sure to irrigate the plants throughout the fall season, and provide a fresh layer of mulch around trees and shrubs to prevent additional moisture loss. Ensuring that the trees and shrubs are receiving adequate moisture is one less stress for the plants.

Ward off pests

Fall is also a good time to take inventory on the past year’s pest problems and symptoms that may have compromised the health of trees and shrubs. To reduce the likelihood of recurring ornamental diseases and insects, remove leaf litter from the area. Pathogens and insects may be harbored in the leaf litter — providing a perfect opportunity for the ornamentals to be re-infested the following growing season. In addition, fall applications of a soil-applied systemic insecticide will not only combat insect pest problems already present, but will also protect the tree or shrub the following growing season.

Insect pests have the innate ability to seek out and feed upon trees and shrubs even when they are healthy, properly maintained and thriving. Though most pests that attack trees or shrubs cause primarily aesthetic damage, some insects, if left unattended, are capable of inflicting significant damage, or even causing death for the tree or shrub.

To protect your trees and shrubs from some of the most harmful insect pests that may impact your geographic region this fall, be on the lookout for the following:

Northeast and Midwest

Emerald Ash Borer

Host plants: All North American Ash species
Signs and symptoms: D-shaped exit holes; damage from woodpecker feeding; thinning of leaf canopy
Damage: Larval feeding underneath bark disrupts transport of nutrients and water
Recommended control: Soil applications of a systemic insecticide such as imidacloprid


Spiraling Whitefly

Host plants: Broad host range; palms, woody ornamentals
Signs and symptoms: Eggs are laid in spiral pattern on leaves; white, waxy material on leaves
Damage: Feeds on plant juices; production of honeydew during feeding will cause growth of sooty mold on leaves; heavy infestation will result in plant health decline and branch dieback
Recommended control: Soil applications of a systemic insecticide such as imidacloprid


Asian Citrus Psyllid

Host plants: Citrus; ornamentals related to citrus such as orange jasmine
Signs and symptoms: Waxy filaments produced by nymphs visible on new leaf growth
Damage: Feeds on plant juices; vectors a deadly citrus disease, Huanglongbing or Citrus Greening;
Recommended control: Soil applications of a systemic insecticide such as imidacloprid; foliar applications of pyrethroid

To gain the most benefits from treatments, it is important to also be cognizant of the common diseases threatening trees and ornamentals in the fall. Black spot, leaf spot, rust, and scab can easily be treated using a broad-spectrum strobilurin fungicide such as trifloxystrobin. This offers both preventative and curative control via weather-resistant mesostemic mode of action.

For diseases such as anthracnose, downy mildew, pine rust, stem and cone rusts, or tip blight, triadimefon-based fungicides offer not only the systemic disease protection that safeguards ornamentals, but also protect against many of the toughest turf diseases — which can help streamline your business model.

Stephanie Darnell is technical development manager for the Insecticides business of the Environmental Science Division of Bayer CropScience LP. She is responsible for insecticide development and technical support for ornamentals and edibles for the Professional and Consumer markets.

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