By Mike Jiggens
Being able to properly diagnose irregularities on home lawns is an
important skill for lawn care professionals to have, but, when in
doubt, there are always agronomists or diagnostic clinics willing to
“People see some symptoms and they automatically think that it’s some sort of biotic issue, like a disease or an insect, and oftentimes it’s really just abiotic disorders,” Dr. Katerina Jordan of the University of Guelph told those in attendance at the third annual Nutrite Professional Seminar in March at Guelph’s Springfield Golf & Country Club.
To be able to distinguish between biotic and abiotic issues is a key first step. Now that traditional pesticide products are no longer an option for use on home lawns, early and accurate diagnosis is especially vital. Prior to the Ontario cosmetic pesticide ban, which was officially enacted in 2009, lawn care professionals could rely on a number of curative options.
“Now with that tool removed, being able to get out there and notice things when they first start and making sure that you properly diagnose things immediately becomes imperative.”
Jordan said that in reality, the biggest “pest” lawn care professionals must deal with is the homeowner. The customer is directly responsible for many of the issues the professional must face during the season.
Being able to recognize the various abiotic issues and having the ability to differentiate them is a huge asset, she said.
“In the end, you want to avoid wasted labour and a waste of products if you put anything down, especially with some of the alternatives which, although are somewhat effective, can be a bit expensive.”
Jordan suggested that when a lawn care professional sees a symptom, he should step back and look for patterns.
“Patterns can tell you so much. Sometimes just stepping back and taking a look at the entire pattern as a whole is really important.”
Patterns can provide plenty of information immediately, she said, adding that if the professional is still unsure of the matter after looking at patterns, he should move in closer and inspect stand symptoms. This could include spots which are small and regular that may or may not come together and coalesce.
Bigger spots are usually distinct as well as patches or rings.
“It may not necessarily tell you what’s happening, but it’s just another piece of that pie.”
Jordan said the fastest way to differentiate between biotic and abiotic issues is to look at signs which are physical evidence of a pest itself. Symptoms are the actual effect of whatever is going on has on the plant.
If grubs are detected, for example, it’s a biotic problem.
She also suggested that lawn care professionals be up on their turf identification, especially when dealing with an insect or disease. There are certain hosts which are susceptible and others that are not.
“Knowing your turf ID is important because if you can note the specific hosts affected, it can actually help you rule out what the problem may or may not be.”
If the professional suspects the problem is biotic, he can look at individual plants for symptoms. This could include leaf spot which are usually distinct little spots or lesions which are elongated. Lesions can appear on the stems, or perhaps a foliar blight or dieback may be detected.
The presence of crown or root rot can be indicative of a number of things, Jordan said, but often it’s a type of root disease.
She said too many lawn care professionals tend to ignore what is happening below the ground and focus on what they see on the surface.
“Half or more of what we see going on above ground is directly related to what is going on beneath that soil.”
Jordan suggested using a soil probe to remove some of the root tissue and see what’s going on.
“Get down there and take a look at your roots and try to take some notes on what you’re seeing.”
If a symptom is detected in which there may be one type microclimate vs. another, it could be another hint as to what might be happening.
The professional should think of any cultural practices that might lead to symptoms, she said. Perhaps scalping was done or another type of mechanical injury was committed. If core aeration had been done recently, there may be thinned areas.
Once all of this information has been noted, the professional should make a list of all possible causes, Jordan suggested.
Weeds may be an issue, but it’s not something that needs to be mentioned as far as diagnosis goes because it will be obvious to the professional that it’s a weed as opposed to grass.
Problems on home lawns are based on the presence of signs, she said, but also the symptoms and environmental conditions. These will help in differentiating between a biotic or abiotic issue. Usually, professionals see abiotic causes such as recent management practices, fertility, environmental conditions, patterns or symptoms, and recent weather.
“If you still can’t figure it out, there’s nothing wrong with sending in a packaged sample to an agronomist or diagnostic laboratory.”
Common abiotic issues include drought stress, waterlogging, salt or nutrient toxicity, nutrient deficiencies, mechanical damage, shade, soil compaction and thatch.
Among common biotic issues are weeds, insects (grubs, leatherjackets, hairy chinch bugs, bluegrass billbug) and diseases (necrotic ring spot, rust, red thread, powdery mildew and leaf spot).
Drought tends to be one of the more common abiotic stressors in home lawns because few are irrigated. Whether the home has an installed irrigation system or not, may homeowners don’t water their lawns either due to watering restrictions or because of the cost.
The problem with drought, Jordan said, is that it produces non-descript symptoms. The turf is off-colour, making it difficult to tell what the problem might be.
“Plants do have many ways of resisting drought,” she said. There could be early seed production. Annual bluegrass does well at avoiding death by producing seed. Some fescues are good at deep rooting which is another way to fend off drought. Kentucky bluegrass has a good dormancy mechanism built into the plant, which is its way of avoiding drought.
Annual bluegrass and creeping bentgrass, on the other hand, are susceptible to drought.
If remediation is to be considered, it’s a good idea to plant drought-tolerant species and cultivars, Jordan said.
Promoting deeper roots will help stave off drought.
“The deeper your roots, the more likely the turf will be to accesss any available water.”
She suggested avoiding high nitrogen levels.
“If you put down a wad of nitrogen at one time, you can get a flush of growth above ground. If you already have a poor root system, that may lead to stress, so you want to make sure you use the right form of nitrogen.”
There’s nothing wrong with letting turf go dormant, especially if the home is located in an area facing watering restrictions.
On the other side of the coin, too much water can lead to waterlogging when the soil becomes saturated, especially if the soil is poor and doesn’t infiltrate well. This may not be a big problem in the short term, but damage will occur if poor drainage allows for waterlogging to happen for extended periods.
Waterlogging leads to reduced oxygen availability to the roots. The plant requires oxygen to respire, and anaerobic toxicity will occur if the oxygen supply is cut off. Anaerobic organisms or bacteria which is able to function in the absence of oxygen produces gases such as methane which are toxic to the plant.
Waterlogging can be worse at certain temperatures than others. If the plant is not actively metabolizing and if temperatures are less than 10 degrees Celsius, there won’t be much effect from waterlogging.
“However, if you do have high temperatures, then a situation like this can actually lead to scalding of the turf.”
Water can heat up and adversely affect the plant.
Different grasses will respond differently to waterlogging just as they do with drought. Susceptible plants include red fescue and annual bluegrass. Creeping bentgrass and Kentucky bluegrass are more tolerant towards waterlogging.
The logical solution toward prevention remediation would be to install or improve drainage on the home lawn, but that might not be practical with most customers. Allowing for increased sunlight will allow the soil to dry out more quickly, and anything that will encourage water infiltration and allow it to move through the profile is recommended. This can be helped by reducing thatch or soil compaction.
Salt toxicity can be an issue when lawns are situated near roads treated during the winter months. Nutrient deficiencies are common with home lawns, leading to less stress tolerance and thin turf.
Thatch can be either good or bad, depending on how much of it there is. A little thatch is helpful in protecting the crowns of the plant and promoting cushioning. Excess thatch, however, leads to shallow roots, disease, soil compaction and reduced infiltration. Thatch can be managed by vertical mowing and deeper, more infrequent irrigation.
Jordan said if the lawn care professional wishes to seek the advice of a laboratory or an agronomist, he should collect a sample and keep it moist yet not wet. Movement of the sample within a container should be restrained, and it is best to send it overnight rather than by conventional mail. Submitting quality photographs of the situation to complement the sample is also advised.