Usually, a top ten list highlights the 10 best of something. Unfortunately, when looking at plant problems, we are looking at the ten problems most frequently seen...the 10 worst!
#1 – Winter Damage (22 samples, 9.8%)
|Freeze damage on Bosnian pine|
Drought injury is an environmental disorder that occurs when more water is lost through leaves or needles than can be taken up by the roots, causing plants to become dehydrated. The cause of drought injury can be due to either cultural (insufficient irrigation) or environmental factors such as prolonged heat, low humidity, drought, wind, and root damage.
tip dieback of needles progressing from the top of the tree down.
13 samples, 5.5%
|Howard F. Schwartz, Bugwood.org|
#4 - Herbicide Injury, 10 samples, 4.3%
|Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org|
Herbicides can reach non-target plants in several ways: via vapor movement from nearby properties, drift of sprays, and through manure or straw mulch. With good cultural care, plants can outgrow sub-lethal doses over one to several seasons.
#5 - Eriophyid mite damage, 7 samples, 3.0%
|Eriophyid mite scabbing on Oak|
Eriophyid mites are tiny (microscopic) mites that feed on plant sap, causing plant damage such as leaf galls, scabbing and distortion. Most years we see finger galls on Linden leaves, but in 2020 we received multiple samples (Maple and Oak) that had these scabbing symptoms due to the mite feeding.
The damage is primarily aesthetic and typically doesn’t warrant control.
#6 - Planting Issues, 6 samples, 2.6%
The most common planting issue that we see is deep planting of both herbaceous and woody plants, evidenced in trees by lack of trunk flare. When roots are planted too deep in the soil profile, then they don’t get enough oxygen. Poor growth, or even death, is a result. Other planting issues can include choosing the wrong plant for your hardiness zone or soil, or planting in the wrong spot. See Planting Trees and Shrubs.
Deep planting (above)
# 7 – Overwatering, 5 samples, 2.1%
When plants are overwatered, water replaces oxygen in the soil, causing oxygen starvation (aka suffocation). Plant symptoms can include leaf discoloration and leaf drop from the bottom up, stunting, root rot, and death. See Environmental Disorders of Woody Plants.
# 8 – Cultural problems, 4 samples, 1.7%
|Sprinkler coverage or malfunction|
“Cultural problems” is a category that we use to include plant symptoms and diagnoses resulting from sub-optimal cultural care (water, fertilizer, core aeration of turf, etc.).
The samples with this diagnosis in 2020 were typically lawns that had become thin & weedy due to improper sprinkler coverage, failure to apply sufficient water to the roots, and lack of aeration. See Lawn Care and Waterwise Landscape Design for recommendations.
Spider mites feed on plant sap, causing leaf damage that ranges from stippling/flecking to scorch, leaf drop and plant death. Providing appropriate water to the plant is the first line of defense.
|Two-spotted spider mites, Frank Peairs, Colorado State University, Bugwood.org|
Tomato Spotted Wilt Virus (TSWV) was reported in both tomato and pepper plant samples. Symptoms of TSWV include distorted leaves with purplish veins, brown to purple spots on leaves, wilting, and yellow to orange/brown rings on fruit.