WEEKLY INSIGHT
Weekly Insight Week 24
Growing Grass in the Desert Starts Here
June 7 - 13, 2026
When Rain Brings More Than Growth:
Understanding Plant Diseases in Lawns, Trees, and Shrubs
If you've stepped outside lately, you've probably noticed the same thing I have.
Everything is growing.
After another half inch of rain overnight and more moisture still in the forecast, lawns are thickening up, shrubs are pushing fresh growth, and trees across West Texas seem to be enjoying one of the best starts to June we've seen in years.
During my morning walk today, the grass was still wet from the night's rain. The landscape looked healthy, vibrant, and full of life.
But whenever Mother Nature provides the moisture that plants love, she also creates conditions that many plant diseases love as well.
Over the next few weeks, some homeowners will begin noticing brown patches in their lawn. Others may find black spots on roses, powdery mildew on crape myrtles, or leaf spot diseases on shrubs and ornamentals.
The question is always the same:
"Why is this happening to my yard?"
The answer may surprise you.
The Disease Triangle
Plant diseases rarely appear by accident.
For a disease to develop, three things must occur at the same time:
• A susceptible plant
• A disease-causing organism
• Favorable environmental conditions
Plant pathologists refer to this as the Disease Triangle.
If any one side of that triangle is missing, disease pressure is greatly reduced.
In other words, a fungus may already be present in your lawn or landscape, but without the right environmental conditions, it may never become a problem.
Why Does My Yard Have the Disease and My Neighbor's Doesn't?
This is one of the most common questions we hear at BES-TEX.
Two neighbors can have the same grass variety, the same shrubs, and receive the same rainfall. Yet one develops disease while the other remains healthy.
Why?
Often, the difference comes down to the environment.
Small factors can make a tremendous difference:
• How often the landscape is watered
• Morning versus evening irrigation
• Amount of shade
• Air movement
• Soil drainage
• Plant stress
• Fertility practices
The fungus may exist in both landscapes.
The environment simply gives it permission to grow.
When Conditions Become Favorable
Many turf managers have long used what is known as the "Rule of 150."
When the daytime high temperature and nighttime low temperature add up to approximately 150 degrees or more, conditions often become favorable for many turf diseases.
For example:
90° daytime high
+
62° nighttime low
152°
This does not guarantee disease.
Instead, it serves as an early warning sign that environmental conditions may be shifting in favor of disease development, especially when humidity and moisture are present.
Think of it as a weather forecast for disease pressure.
What Does a Fungicide Actually Do?
One of the biggest misconceptions in our industry is that fungicides cure damaged plants.
Unfortunately, once a leaf has been damaged by disease, it will not suddenly turn green again.
The role of a fungicide is to stop the disease from spreading and protect healthy plant tissue.
When applied properly, fungicides help preserve healthy growth while the plant naturally replaces damaged tissue over time.
Understanding Contact and Systemic Fungicides
Not all fungicides work the same way.
Contact fungicides remain on the outside surface of the plant and act as a protective shield. They work exceptionally well as preventative treatments but require thorough coverage and may need to be reapplied after heavy rainfall.
Systemic fungicides are absorbed into the plant and move through plant tissues. They typically provide longer residual control and help protect new growth as it develops.
Both have an important place in a disease management program.
Why Do Labels Recommend Reapplication Every 7 to 14 Days?
This is another question we hear frequently.
The answer is simple.
Fungicides do not last forever.
Rainfall, irrigation, sunlight, plant growth, and natural microbial activity gradually reduce their effectiveness. At the same time, many diseases continue producing new spores whenever environmental conditions remain favorable.
Repeat applications help maintain a protective barrier until disease pressure subsides.
Four Active Ingredients Every Homeowner Should Know
If you only remember four fungicide active ingredients, these are a great place to start:
Propiconazole
Excellent for many common lawn and ornamental diseases.
Azoxystrobin
Broad-spectrum disease protection with excellent preventative activity.
Myclobutanil
A proven performer for powdery mildew and many ornamental diseases.
Phosphites
Often used to help manage root diseases associated with excessive moisture.
The Bottom Line
The best disease control program is not always a fungicide program.
Proper watering practices, adequate sunlight, good drainage, proper fertility, and reducing plant stress are often your first and most effective line of defense.
Remember this:
The fungus is often already there.
The environment determines whether it becomes a problem.
Thank you for allowing BES-TEX Supply to be part of your lawn and landscape success. We appreciate the opportunity to share these weekly insights and hope they help you better understand your lawn, landscape, trees, and pest concerns.
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As always, if you have questions, bring in a sample, send us a picture, give us a call, or stop by the store. We are here to help.
Thank you for your continued support of BES-TEX Supply.
Monte Sims
BES-TEX Supply
4512 Adobe Dr.
San Angelo, TX 76903
325.653.1300
www.BES-TEX.com
Payment Terms: At BES-TEX Supply, we accept all major credit cards (MasterCard, Visa, Discover, American Express), as well as personal checks & cash. Please note that all sale items must be paid for at the time of purchase. We do not offer net 30 terms on sale items.