Common causes of abiotic disorders include too much or not enough water, compacted soil, nutrient deficiency (often caused by imbalanced soil pH), excess soil salinity, too much heat or sunlight, herbicides, air pollution, and mechanical injuries.
Abiotic disorders can develop for several reasons:
- the site was not well prepared before landscaping,
- the plants were improperly planted,
- the plant species is not well adapted to conditions at that location,
- the plants did not receive the correct cultural care.
Avoid abiotic disorders by giving plants the right amount of water, sunlight, and nutrients. You must water plants properly, and the soil must drain well. The soil must contain the correct nutrient levels, pH, and salinity. Fix any extreme light or temperatures issues like too much sunlight. Protect plants from herbicide and fertilizer damage as well as from mechanical injuries.
When you suspect an abiotic disorder, find out both the species and variety of the plant so you know the plant's expected appearance and its specific cultural needs. Inspect the plant and surrounding plants for symptoms. Some abiotic disorders can be recognized by their characteristic damage symptoms (e.g., distorted, discolored, or dying foliage). However, diagnosing the cause of disorders can be difficult. Plants will react differently to abiotic issues depending on their age and specific variety. Different abiotic causes can produce the same symptoms, and more than one cause can affect plants at the same time.
To solve plant problems, it's important to distinguish abiotic disorders from similar-looking damage caused by pests such as insects, mites, nematodes, pathogens, and vertebrates. See Table 1 for details.
|Plants affected||Unrelated||One type or closely related|
|Plant age||Various ages||Same age more likely|
|Pattern of symptoms||Regular or uniform||Random or irregular|
|Rate of development||Sudden onset||Slow, worsens over time|
|Spread||Does not spread||Infectious, spreads on host over time|
|Signs||No evidence of pest or pathogen||Presence of pest, mycelium, mushrooms, rust, pustules, bacterial ooze, honeydew, frass|
For more information about abiotic plant problems, see the UC ANR publications Abiotic Disorders of Landscape Plants and Pests of Landscape Trees and Shrubs. Content adapted from Abiotic Disorders of Landscape Plants and Pests of Landscape Trees and Shrubs.
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- Author: Nick Volesky, Utah State University Vegetable IPM Associate
- Posted by: Elaine Lander
- Blossom drop occurs when daytime temperatures exceed 90°F and nighttime temperatures stay above 72°F for several days, causing tomato pollen to become nonviable and blossoms to dry out and drop without producing fruit. Blossom drop can also occur if there is no pollination or temperatures dip below 55°F at night. It can be prevented by setting up shade cloth to protect plants during the hottest periods of the growing season.
- Blossom end rot is the death of tissue on the blossom end of tomato fruits, appearing as dark brown-black target-like rings. It occurs when plants are unable to move enough calcium from the soil throughout the plant, with the tomato being the farthest location and thus getting the least calcium. Blossom end rot can be prevented by evening out the watering to allow the plant to continually uptake water and calcium. Consider using mulch around the plants to prevent water loss.
- Cat-facing is when tomatoes are distorted and misshapen. The damage is caused by one of many factors such as blossom scarring, high nitrogen levels, temperature fluctuations, excessive pruning, or insect feeding. Avoid “cat-faced” fruit by growing cultivars that are less prone to cat-facing (heirloom varieties tend to be more prone). Provide adequate growing conditions and good pest management.
- Cracking and splitting on tomatoes occur when there are rapid changes in soil moisture levels which can cause the fruit to expand quicker than its skin can grow. Openings can leave fruit susceptible to insects and diseases. Prevent this by providing plants with an even watering schedule.
- Cold or freeze damage occurs when tomato plants are exposed to temperatures below 35°F, where plant cells expand, freeze, and die, causing interveinal spots. Leaves on established plants may turn purple and dark. After transplanting, follow weather forecasts closely in the spring and cover plants to protect from any expected frosts.
- Green shoulders appear when tomato fruits are fully ripening, but the top “shoulder” ends remain green and yellow. This is simply caused by genetics and environmental conditions (high temperatures and exposure to direct sunlight).
- Herbicide damage occurs when an broadleaf herbicide contacts the plant directly or indirectly via drift or vapors. Some herbicides that are sprayed in hot temperatures can volatilize and move as a vapor for long distances, affecting vegetable crops. Herbicide damage symptoms include small misshaped leaves that are thick and tightly curled.
- Horn/nose Development is a physiological and genetic disorder. A few cells divide abnormally and the fruit produces an extra locule (interior segment within the tomato). This mutation often occurs in very cool or very hot temperatures during tomato fruiting.
- Edema/oedema is a physiological disorder identified by watery blisters or swellings that form along the leaf veins. It is induced by high relative humidity and light quality. Because of this, edema is most commonly observed in enclosed settings such as greenhouses.
- Leaf curling is associated with various environmental stresses, viral infection, or herbicide damage. Environmental stresses include excessive moisture and nitrogen, heat, drought, severe, pruning, and transplant shock.
- Sunscald on tomatoes begins as yellow/brown discoloration on the sun-exposed side of the fruit. Eventually, the flesh becomes tough, white, and leathery. This damage exposes the tomato to potential rot pathogens.
- Zippering is an abiotic condition that occurs when the flower anther sticks to the developing fruit as it grows. Symptoms include a thin brown longitudinal scar (with transverse scars) extending down the fruit, resembling a zipper. Zippered fruits that are intact are still edible; however, openings that ensue can allow pathogen infections or further insect damage.
You can also register for our upcoming webinar on plant diseases Thursday, July 15 at 1:00pm PDT. Attendance is free and open to the public but registration is required. See Urban & Community IPM webinar website for more details.
- Author: Janet Hartin
- Posted by: Elaine Lander
Your customers want their lawns to be beautiful and functional (Figure 1) but dead patches or other problems sometimes occur. Figuring out the cause of turfgrass damage can be a challenge since many plant pathogens affect grasses as well as numerous abiotic (non-living) disorders. can impact the quality of lawns, playing fields, and other turf areas.
Keeping turfgrass healthy is essential for reducing damage due to both diseases and abiotic disorders. Following recommended practices regarding irrigation scheduling, integrated pest management, fertility, mowing height, soil aeration, and other measures is your customer's best line of defense.
Identify the cause of unhealthy grass
Ask your customer the following questions to help determine whether the cause is due to abiotic or biotic issues.
- Is the problem confined to one area or across the entire lawn?
- When did the problem begin? Could it be seasonal?
- Have there been unusual changes in the climate or microclimate?
- What are the lawn care practices? Have there been recent changes?
Some answers to these questions include:
- Too much or too little water that may impact several plant species irrigated on the same valve as the turf.
- Herbicide injury and fertilizer applications can also impact several plant species growing in the lawn area.
- Many fungi resulting in plant diseases are confined to one species of turf and often do not impact surrounding plants.
Knowing that damage from abiotic causes does not spread can be helpful. Disease and insect infestations almost always spread outward from the initial point of damage. Also, diseases and insects can often be identified by specific symptoms.
In addition to the symptoms, damage from diseases often leave telltale signs of the pathogen. Examples include light colored cotton-like growth on leaves, areas of chlorotic (yellow) grass surrounding healthy appearing grass, rotted roots and crowns, and hard structures called sclerotia.
Nutrients. While over-fertilized lawns often show no damage symptoms, nitrogen-deficient lawns appear chlorotic, thin, and are more prone to fungal diseases such as dollar spot. Most turfgrass needs nitrogen fertilization during the active growing season to stay healthy and attractive. For specific turf recommendations, see the UC Guide to Healthy Lawns at ipm.ucanr.edu/TOOLS/TURF/
Micronutrients such as iron and zinc may also be required. Keep in mind that these and other micronutrients may be temporarily “tied up” in the soil due to high pH (alkaline) but become available to the plant if pH is reduced by adding sulfur or ammonium sulfate.
Another common type of fertilizer damage occurs from uneven application of nitrogen-containing fertilizers across the turf. This results in streaks of dark green grass next to skipped areas that remain light green and later turn yellow (Figure 3).
Dog Urine. Damage from animal urine (especially dogs) occurs most often on dry turf, especially during periods of high temperatures and prolonged drought. Cool season grasses tend to be more impacted since they require 25% more water than warm season grasses. Damaged turf appears wilted and grayish-green initially. Soon it becomes brown and may die depending on concentration, type of grass, turf hydration, and water leaching. Typical damage is a small center of brown grassless than 6 inches apart surrounded by a dark green ring (Figure 4). Contrary to popular lore, female dogs are not the only canine culprit, since puppies of both sexes squat the first year or so of life.
While damage from animal urine can resemble that from dollar spot and other fungal diseases, it has a darker green outer ring that is often much taller than the surrounding grass and does not have fungal structures called mycelium (Figure 4).
For specific information on managing lawn damage caused by dog urine, see UC ANR Publication 8255 “Lawns ‘n' Dogs” at anrcatalog.ucanr.edu/Details.aspx?itemNo=8255.
Remember that proper turf maintenance can greatly reduce the incidence of abiotic and biotic disorders and that more than one factor may be responsible for the damage. Since both insects and diseases often attack plants already stressed by abiotic factors, addressing abiotic disorders is essential to reducing the impact of insects and diseases. Grass that is already suffering from abiotic disorders can be susceptible to disease. This can result in pest and disease outbreaks that otherwise may have been avoided. See to ipm.ucanr.edu for UC IPM Pest Notes that can help you identify both biotic and abiotic problems.
Days are getting shorter and evenings cooler as winter approaches. Sweater weather also means a change in the to-do list around the yard.
Here are a few things to consider when preparing your landscapes and gardens for winter.
- Protect sensitive plants from cold injury when freezing or frost is predicted. Cover plants with cloth or a similar material at night, leaving the covers open at the bottom so heat from soil can help warm plants.
- When frost or freezing is expected, irrigate dry topsoil at least 3 days before the cold weather to increase the soil's ability to retain heat.
- Adjust watering schedules according to the weather and your plants' changing need for water.
- Reduce irrigation frequency or turn off systems if rainfall is adequate. Excessive water or poor draining can lead to root rot and other plant diseases.
- Irrigate deeply but infrequently if the winter is dry.
- Manage weeds using nonchemical methods such as hoeing, hand weeding, or mowing.
- Apply organic mulch such as wood chips or bark chips where it is thin and where soil is bare beneath trees and shrubs. Mulches prevent weed seed germination by blocking sunlight.
- Clean up old fruit and remove fallen leaves. These sanitation practices help prevent disease and manage insects that may be problematic in springtime.
- Prune deciduous trees and shrubs such as apple, crape myrtle, rose, and stone fruit. Pruning allows for good ventilation and is important for maintaining the structure and health of trees and shrubs.
Looking for additional winter guidelines? Subscribe to our Seasonal Landscape IPM Checklist for a monthly email with pest management tips for your area.
- Author: Ben Faber
It's winter time and avocados and other subtropicals are prone to frost damage. Little trees especially that haven't developed a canopy that can trap heat are the most prone. So it gets cold and all the orchard looks fine, but there's one tree that doesn't look right and in a couple of days it really stands out.
Here's an example of a year old tree that turned brown and it actually looks like it was doing better than the trees surrounding. It's bigger and has a fuller canopy..... or at least it did.
But there's all the symptoms of frost damage - bronzed leaves and dead tips.
A week after the cold weather, there is already sunburn damage on the exposed stems. See the brown spots on the upper fork? That will soon turn all brown and dry up.
This is still a healthy tree with green stems, in spite of the burned leaves. Now is the time to protect the tree from sunburn damage. This is what can kill the little tree. Time to white wash it.
Why did it happen to this one tree? Maybe it was a little bigger and needed more water than the surrounding trees. Maybe sitting on a rock and didn't have enough rooting volume for water. Maybe a touch of root rot (although the roots looked pretty good even for winter time). And there were ground squirrels in the area. Easy to bklamne them.
Listen to the sound of winter frost control
And when freeze damage gets extreme