Extension Bulletin E-2996 • New • June 2007 Abiotic Plant Disorders  Symptoms, Signs and Solutions A Diagnostic Guide to Problem Solving Robert E. Schutzki Bert Cregg Department of Horticulture Departments of Horticulture and Forestry Michigan State University Michigan State University

The term “abiotic disorders” refers to a wide array of plant problems. We use the word “abiotic” to indicate that the symptom is not caused by a biological agent such as an insect, mite or patho- gen. Abiotic disorders are associated with non-living causal factors such as weather, soils, chemicals, mechanical injuries, cultural practices and, in some cases, a genetic predisposition within the plant itself. Abiotic disorders may be caused by a single extreme environ- mental event such as one night of severe cold following a warm spell or by a com- plex of interrelated factors or events. They can also be caused by chronic con- ditions such as a prolonged drought or plant selection inappropriate for the ex- isting site conditions (e.g., planting an acid-loving species in an alkaline soil). Abiotic plant problems are sometimes velop severe leaf yellowing or chlorosis A b i o t i c termed “physiological disorders”. This re- and have reduced rates of photosynthesis. plant disorders flects the fact that the injury or symptom The cumulative and subtle nature of are associated we see, such as reduced growth or crown many physiological disorders can often with non-living causal factors. dieback, is ultimately due to the cumula- make them difficult to diagnose. An ex- tive effects of the causal factors on the treme event such as a severe late freeze or physiological processes needed for plant a misapplied herbicide is an obvious growth and development. When a tree is “smoking gun” to indicate the underly- affected by severe drought, for example, ing cause of injury. More often, however, water stress will result in closure of the diagnosing abiotic problems requires pores, or stomata, on the leaf. This con- careful consideration of plant and site serves water in the leaf but also reduces factors through a process of elimination the rate of photosynthesis and the ability to determine the source and potential of the plant to produce sugars for growth. remedy for the problem. If the drought stress occurs during hot Abiotic disorders are usually classified weather, stomatal closure also limits the by causal factor or symptom. In this cooling effect of transpiration, and leaf bulletin, we will present abiotic disor- scorch may occur. Nutritional imbalances ders whose origins are due to biological/ also limit growth by reducing photosyn- botanical factors, environmental (climate thetic rate and other physiological and and weather) conditions, soil conditions, metabolic processes. Some plants, such as chemical applications, animal damage and pin oak, have a limited ability to take up cultural practice. We will also provide a iron under alkaline soil conditions. Iron is framework for diagnosing problems and essential for synthesis of chlorophyll, so suggest steps to mitigate abiotic injuries pin oaks on alkaline soils frequently de- before or after they occur. For unknown reasons, some of these  Biological/Botanical mutant cultivars exhibit a tendency to The genetic makeup of produce shoots that revert to their spe- a species is expressed cies type. Genetic reversions are fairly through its physiological common on dwarf Alberta spruce and and morphological char- Harlequin Norway maple. To maintain acteristics. Whether these the cultivar characteristics, genetic rever- characteristics are per- sions need to be pruned out quickly and ceived as normal or ab- completely when they are observed. normal depends on the individual circumstances Chimeras and location where they Chimeras are botanical abnormalities are found. Understand- that are often confused with nutritional ing the basis for these or chemical disorders. “Chimera” is a characteristics can be use- term used to describe a single plant with ful in determining wheth- two genetically different tissue types. er they need to be Leaf variegation is the most common addressed and can aid in example of chimeras in plant species. outlining a course of ac- The difference in foliage color and the tion. In many cases, these banding of those colors are due to cell characteristics are a fact of mutations in the meristematic tissue nature and simply need to layers. Chimeras can be stable, in that the be appreciated for what genetic differences are consistent and re- they are; in other cases, producible. These chimeras have spawned they can be altered or cor- numerous of our variegated plant culti- rected by simple measures. vars. Chimeras can also be unstable and Here are some common unpredictable, surfacing sporadically on abiotic abnormalities that either shoots or individual leaves. The Genetic reversion on are biological/botanical in Bumald spireas are known for the spo- Harlequin maple. origin. radic appearance of unstable leaf chimeras. The stability of the chimera depends on Genetic mutations and the tissue layer where the mutation oc- reversions curs. If you discover variegation on an Genetic anomalies are prevalent in individual stem and not over the entire the plant world and often garner much plant, it is possible that it is a chimera and attention. For example, not an abiotic disorder related to plant seedling growers often nutrition or chemical injury. find mutants in their nursery beds. Albino seedlings are common seedling mutants. Be- cause they lack chloro- phyll, these seedlings quickly die off once they exhaust energy reserves from the seed. However, many mutants are stable and sustain growth. These stable mutants can Chimera on Anthony Waterer spirea. exhibit unique form, foli- age, flower, stem and other characteristics that Leaf abscission and retention warrant their develop- Leaves emerge in the spring, func- Genetic reversion on ment and introduction tion during the growing season, turn dwarf Alberta spruce. into the trade. colors and drop in the fall. Leaf drop occurs whether the plant is deciduous systems, signs of graft incompatibility or evergreen; it just happens with dif- may be visible as an uncharacteristic in-  ferent aged leaves. There are times tensity of the fall color. Disruption of when leaf drop or retention is normal translocation leads to a buildup of sugars and times when it may be related to a during leaf senescence that intensifies fall plant problem. foliage color. This is especially the case Leaf abscission or drop is triggered in on Acer rubrum cultivars with known in- the fall by seasonal changes in day- compatibility problems. Graft incompat- length. Chlorophyll degrades, and the ibility issues on these Acer rubrum plant hormones abscisic acid and ethyl- cultivars led to production on their own ene cause an abscission layer to be roots. Graft incompatibility remains a formed at the base of the petiole. In concern in fruit tree production. Incom- evergreen species, needles usually func- patibility is not easily detected and can tion for 2 to 3 years, depending on the surface at various times in a plant's life. species. Normal leaf yellowing and ab- Unfortunately, for many it surfaces when scission occur on the insides of the stem the trees are mature and affected by on 2- or 3-year-old wood. Yellowing or wind or some other environmental con- browning of needles on the shoot tips is dition. Graft incompatibility can result a sign of problems. If a stem or leaf is in semimature trees snapping off at the injured or dies before seasonal changes base in wind storms. Failure of the tis- occur, abscission layers will not form and sue union is visible at the trunk/root col- leaves will remain on the stem. Leaves lar. On plant species with known remaining on isolated stems in the fall or problems, check on the budding or graft- winter are signs of stem or leaf problems. ing practices during production. Anoth- Stems may be girdled by an insect borer er form of incompatibility occurs when or mechanical injury, causing a break in there are differences in growth rates be- Leaf retention vascular connections resulting in stem tween the scion and the understock. on oak. death and leaf retention. An early kill- These differences can lead to dispropor- ing frost prior to the formation of the tional growth at the junction of the two abscission layer may cause dead leaves to tissues. be retained throughout the winter. In some deciduous plant species, leaf Galls and burls retention is a normal characteristic. Galls and burls are ab- Marcescent leaves are the dead leaves normal growths on retained by some plant species. Typical woody plants. They can examples of genera exhibiting marces- occur on branches, trunks cent leaves are oaks and beeches. Species and, in some cases, on within these genera do not complete the roots of woody plants. formation of the abscission layer until Galls may be caused by the following spring. Leaves will fall an insect or disease; how- when bud break occurs and stems resume ever, the origin or causal Proliferation of trunk sprouts growth. If leaf retention is a concern, factors for burls and other leads to callus buildup. identify the plant species, check for evi- callus outgrowths are dence of stem injury, and review recent unknown. Abnormal weather conditions. growths form through a proliferation of cells. Graft incompatibility These cells continue to Graft incompatibility is due to the fail- develop and do not dif- ure of the bud or graft union between a ferentiate into normal tis- scion and an understock. For unknown sue types. In some cases, reasons, the tissues of the two plant parts the outgrowth results do not form a stable union. Failure of the from a cluster of shoots. Callus knob formed from union disrupts translocation in both the Each year, new shoots are reoccurring trunk sprouts. xylem and phloem and influences plant initiated and increase the performance with age. In production layers of the mass. Branch architecture  Genetic makeup contributes to branch architecture and the angle of attach- ment in plant species. Branch angle is a predictor of wood strength and a plant’s ability to withstand compromising envi- ronmental conditions. Even though the loss of branches may be due to wind or ice load, the genetic predisposition for weak branch or wood strength is the in- herent basis for the problem. Common knowledge tells us that vigorous upright branches with narrow attachment angles are prone to storm damage. Horizontal branch angles offer potentially greater wood strength. To ensure the stability and longevity of species with narrow branch angles or Leaf curl on broad-leaved evergreen multistemmed up- due to low-temperature injury. right crowns, correc- tive pruning should be performed on a semiregular schedule. Consider cabling or bracing on plants too old for corrective pruning. Weak branch angle.

Environmental Low-temperature injury on ground cover. (Climate and Weather) Climate and weather are certainly un- predictable, as are their impacts on plants. Climate and weather present a complex of environmental conditions and encompass a range of potential injuries. Fortunately, experience and our ability to learn from the past aid our preparation. Understand- ing climate and weather’s impacts on plants involves plant science, a little me- teorology, a dash of physics and maybe Low-temperature injury on boxwood. some chemistry. These disciplines set the foundation for our dealing with the inter- related environmental factors of tempera- ture, light, precipitation and air flow, and their potential direct and indirect effects.

Low-temperature injury Low-temperature impacts on plants can be classified as chilling or freezing. Chilling injury or chilling stress, as it is often termed, is associated with tempera- tures above freezing but low enough to cause injury. Chilling injury is due to a Low-temperature injury on sudden drop in temperature during an deciduous shrub. active period of plant growth or develop- Understanding low-temperature injury ment. The greater the drop in tempera- begins with an examination of cold har-  ture from normal, the more likely injury diness. Cold hardiness refers to a plant’s will occur. The extent of the injury may ability to withstand cold temperatures cause a reduction in photosynthesis or without sustaining injury. The level of other metabolic processes, an alteration in hardiness that a plant can attain is based growth or death of the exposed plant tis- on genetics, preseason conditioning and sue. For example, a substantial drop in its current condition. The genetic origin temperature during new shoot growth of a plant contributes to its ability to and leaf expansion may result in damage "harden". Plants of a given species origi- Chilling injury on to the terminal meristem and a loss in nating from warmer climates may not be newly emerged shoot growth. Other signs of chilling in- as cold hardy when moved into northern leaves of ginkgo. jury may include wilting, desiccation regions as the same species from north- and/or a physical distortion of plant ern regions. The same is true for heat parts. Chilling injury is less serious than tolerance when northern plants are freezing injury on most of our herba- moved to the South. Origin, not pro- ceous and woody plants. Plants can usu- duction location, is the governing factor ally grow out of the damage inflicted by in determining hardiness capability. chilling injury. Preseason conditioning refers to the Freezing injury is easier to identify physiologic and metabolic changes that and a lot more damaging. It is caused by occur within a plant as it begins harden- subfreezing temperatures. The impact of ing. The process leading to cold harden- subfreezing temperatures may be felt from ing is generally considered a three-stage as little as one overnight episode or from process. The first stage occurs at the end a more sustained exposure episode. Plants of the growing season. Growth has subjected to subfreezing temperatures ceased, plants have formed terminal buds, may exhibit ice formation in the vascular and carbohydrates are accumulating in vessels, in the spaces between the cells stem and root tissues. Short days and and/or within the cells. The extent and cool night temperatures of early autumn pattern of ice formation vary with the begin the acclimation. During acclima- plant tissue and its condition. Ice forma- tion, metabolic changes occur within the tion in the spaces between cells is usually plant that allow it to withstand lower not fatal, but it causes water to leave the temperatures. During the initial stages of cells, causing dehydration. If the freezing acclimation, however, hardiness levels episode is cold and long enough, it can may be lost as easily as they were obtained result in freezing within the cells. Inter- if temperatures rise or other environmen- nal or intracellular freezing ruptures tal factors promote the resumption of membranes and leads to cell death. Freez- growth. Acclimation continues and har- ing damage begins with dehydration and diness tolerance increases with consistent ultimately ends in plant tissue death. exposure to temperatures at or slightly be- Typical signs of freezing injury are a black- low freezing. The final stage, the deepest ened/brownish discoloration or bleaching level of cold hardiness, is achieved after of plant tissue. The severity of the freez- prolonged exposure to subfreezing tem- ing damage depends on the type of frost peratures. Plants are said to be at mid- Late frost injury. injury and the plant parts affected. If the winter levels when they reach their freezing injury kills a significant number maximum cold tolerance for a given sea- of buds or cambial tissue, the plant may son. In the Midwest, maximum levels of die outright or suffer so much crown hardiness are usually achieved by early die-back that it becomes unusable or un- January. As spring approaches, plants be- acceptable in the landscape. More com- gin to deharden or lose cold tolerance monly, however, freezing injury may be with increasing temperatures. Late frosts limited to flower buds and minor shoot can cause injury during this dehardening dieback. This damage may require cor- phase when plants begin to break bud and rective pruning and time to allow the initiate shoot growth. Remember that plant to grow out of the damage. plant parts differ in their cold tolerance. Flower buds usually do not achieve the  hardiness levels that vegetative buds and stem tissue do. The last factor contributing to a plant’s ability to achieve maximum cold hardiness is plant health. Healthy plants achieve their cold hardiness potential; stressed plants may not. It is important to note that plants stressed by drought, flooding, nutrient deficiencies, trans- plant shock or pest problems may not become fully hardy. Any situation that reduces a plant’s Frost crack. ability to produce or store carbohydrates may influence its ability to attain levels necessary to avoid low-temperature injury. The best insurance for hardiness is plant health. In summary, genetics set the foundation levels for low-temperature tol- erance of a plant. Preseason conditioning and plant health determine whether a plant can approach these levels. Frost cracking.

Sunscald and frost cracking Winter desiccation Sunscald and frost cracking are the Winter desiccation is not considered a result of the interaction of light and direct result of low temperature but orig- temperature. inates from the interaction of tempera- They are caused by thawing and ture and wind. As the name implies, freezing due to a rapid fluctuation in winter desiccation is actually a form of stem temperatures. Exposure to after- drought stress. Desiccation occurs when noon sun causes an increase in stem water absorption by the roots can not re- Sunscald and temperature and the subsequent thaw- place water loss through the foliage, buds frost crack. ing of stem/trunk moisture. As the sun or stems. Transpiration and evaporation sets, temperatures drop rapidly. If the from plant parts increase when tempera- temperature drops below freezing, ice tures rise above freezing. This is espe- crystals rupture internal tissue. Sun- cially true on bright, sunny, windy days. scald and frost cracking occur from the If soils are frozen, water absorption can same causal conditions. In sunscald, the not replenish plant tissue moisture, and cambium, phloem and xylem are dam- dehydration and eventual desiccation in- aged, a sunken area appears on the jury occur. Signs of desiccation begin trunk, but the bark is not split. Frost with leaf curl or wilting, and progress to cracking exhibits the same internal dam- a browning of leaf margins and/or bud age with vertical splits in the bark. The scales. If conditions are severe or persis- splits can reopen and close with changes tent, browning will consume the entire in air temperature. As temperatures in- plant part. If snow cover is present, a crease in spring, the bark tissue dries tell-tale snowline above which damage and the cracks remain open. Thin- occurred can be observed on the plants. barked plants are prone to sunscald and Desiccation usually affects the foliage of frost cracking, especially when subjected broad- and narrow-leaved evergreens; to southwest exposures. Tree wraps can buds and stems for the most part are not minimize sunscald and frost cracking, affected unless adverse conditions are but thin-barked plants may always be prolonged or compounded by freezing susceptible to this problem if environ- injury. mental conditions favor temperature Desiccation injury varies with plant fluctuations. species, plant part, soil moisture content, Midwest is early to mid-January. A good time to consider applying anti-transpirants  is during our typical January thaw. Degradation of the anti-transpirant due to weather may require reapplication to extend the protection through the criti- cal period.

Frost heaving Frost heaving results from the alternate freezing and thawing of soils. Heaving exposes the roots to cold and desiccation and is especially a problem on newly planted or shallow-rooted plants. Fall- Winter desiccation on fir. planted ground covers, perennials and small container shrubs are highly vulner- able. Ground cover plugs and small con- tainer plants should be fully planted in soil. This may sound obvious, but with a tendency to plant high, these plants are often found planted in the mulch rather than completely surrounded by soil. In addition, a uniform mulch layer aids in preventing rapid soil temperature fluctua- tions. In larger container plants, planting high in the mulch layer may expose the upper level of the root system enough to influence plant quality the following spring. Proper planting technique is the Upright branches of arborvitae are Winter desiccation on broad-leaved best defense against frost heaving. tied to prevent evergreens. snow and ice Snow and ice injury during depth of frozen soil, snow cover and Ice and snow accumulation on branch- winter. wind velocity. Desiccation is common es can cause internal splits or cracks, bark on narrow- and broad-leaved evergreens. tearing and/or breakage. In the Midwest, it occurs for the most Plant architecture, branch- part when the depth of frozen soil in- ing structure and wood creases in mid- to late winter. Desicca- strength can be predictors tion injury can be minimized or prevent- of damage from excessive ed by protecting plants with screening or snow or ice load. Unfor- applying an anti-transpirant. Wrapping tunately, hidden cavities or screening not only protects from wind in the wood or flaws in Birch is often temporarily bent by but helps minimize the degree of tem- branch attachment can in- snow and ice loads on branches. perature fluctuations on the plant parts. crease the damage poten- Wrapping protects the entire plant; tial. Plants with multiple screening is usually positioned to inter- stems can be tied to pro- cept prevailing winds. Wrapping may be vide support. This may be the smart horticultural alternative on especially helpful on up- prized ornamentals or in high-profile right narrow-leaved ever- landscapes. Anti-transpirants are anoth- greens. Excessive amounts er viable means of protection, but keep of snow can be carefully in mind that they must be applied and removed to alleviate the allowed to dry at temperatures above stress on lateral branches. Ice load on pine. freezing. Application should be made Ice should be allowed to Photo: Erich G. Vallery, USDA Forest Service, before we anticipate injury, which in the melt naturally. Branches www.forestryimages.org become extremely brittle when laden with quirements of some species, causing iso-  ice. Mechanically removing the ice may lated out-of-season flowering when the increase the amount of injury. Once the stress is relieved. ice has melted, the branches will usually Plants can also be subjected to sun- return to their normal positions. burn when shaded foliage is exposed to sunlight during hot, dry periods. Leaves Drought and heat emerge and fully expand in the canopy Moisture stress and extreme heat can of plants over the course of spring and greatly reduce plant growth, especially early summer. Leaves develop and ac- caliper growth. Heat can directly injure climate to light levels. Exposing shaded plants in extreme conditions, but the leaves to full sun during periods of high principal effect of heat is light and moisture stress can produce a increased water loss and sunburned appearance on the foliage. plant moisture stress. To avoid summer sunburn on foliage, Moisture stress can cause do not prune during hot, dry periods significant mortality, par- unless soil moisture levels are adequate- ticularly soon after trans- ly maintained. planting. Wilting is the To understand plant water relations, it most common initial is important to remember that water symptom of drought forms a continuous path from the soil stress. Hardwood leaves through the plant and into the atmo- Wilting of conifer leaders. and conifer leaders will sphere. This is often referred to as the curl or droop. As drought soil-plant-atmosphere continuum. Any progresses, hardwood factor that reduces water uptake from the trees may begin to shed soil – such as low soil moisture, loss of leaves, and conifers may roots during transplanting or frozen soil – begin to drop interior or increases evaporative demand and needles. Drought stress, transpiration to the atmosphere – such as however, reduces growth high temperature or low humidity – can before visible symptoms increase plant moisture stress. such as wilting or leaf shedding become appar- Flooding ent. Even moderate stress Though we usually think of drought can cause the stomata on as a limiting factor for plants, excess wa- the leaves to begin to ter can also be a problem. Plants vary close, reducing photosyn- widely in their tolerance of flooding. thetic production. Caliper Many bottomland species can survive growth is highly sensitive for months with their roots under wa- to water stress because cell ter; other species may be killed by only Sunburn on summer foliage. turgor is required for ra- a few days of inundation. Flooding dial expansion of new causes several problems for plants that wood cells formed by the are not flood-tolerant. Without oxygen, cambium. In fact, the roots begin to undergo anaerobic respi- high sensitivity of radial ration, which results in the production growth to moisture forms of toxic compounds in the plant. Plants the basis of dendrochro- undergoing water stress may exhibit nology, the science of us- symptoms such as wilting that are simi- ing tree rings to recon- lar to symptoms of drought stress. Pre- struct past climates. mature fall color is typically a sign of Drought and heat stress moisture stress, either too much or not can also cause some plant enough. Excessive rain, standing water species to enter into an and poor drainage in late summer can imposed dormancy. This initiate premature fall color on the af- mild state of dormancy fected plants. The same symptom ex- Leaf scorch on oak. can satisfy the chilling re- ists for plants in severe drought stress. One of the prime indicator species for Hail shreds and tears susceptible these types of summer moisture stress is plant parts. It affects leaves, young  Euonymus alatus ‘Compactus’, burning stems and branches, and in severe bush. storms with large hail, it can damage or bruise bark. Damage from hail is Lightning and hail usually immediate and short-term. No Summer storms are a normal occur- treatment is necessary unless light rence in the Midwest, and with them pruning is needed to remove broken come lightning and, in some cases, hail. stems and branches. Trees in particular can be killed out- right or severely damaged by lightning strikes. When lightning strikes a tree, it Soils can fracture and splinter the wood or An understanding of plant/soil travel down from the entry point to the relationships is key not only to ground, carving a groove in the con- solving problems but to avoiding ductive tissue and bark. The extent of them in the first place. the injury depends on the intensity of the lightning, where it enters, the mois- Soil type ture level in the tissue and the wood “Soil texture” refers to the characteristics. Recommendations for mixture of sand, silt and clay treating lightning strikes are relatively particles in the soil. It influ- simple: clean the damaged areas, re- ences aeration, water retention, moving splintered wood and tracing drainage and nutrient-holding loose bark back to firmly seated bark, capacity. Soil texture and its re- and provide cultural practices that in- lationship to water movement vigorate and promote plant growth, through soils is one of the most such as irrigation and fertilization. important factors leading to abi- otic plant problems. We often hear the phrase “moist, well- Death due to drained soils” poor soil drainage. when referring to plant preferences. Un f o r t u n a t e l y, this condition is not the rule in most planting sit- uations. Sandy soils need amend- ments to increase water- and nutri- ent-holding capac- ity. Clay soils Chlorosis on pachysandra due to excessive moisture stress. need alterations to facilitate drain- age. A thorough examination of soil physical and chemical proper- ties can aid in avoiding common problems associ- Lightning strikes can result in ated with water extensive damage to bark and deficits, flooding underlying cambium. and nutrient dis- Photo: Robert L. Anderson, USDA Forest Service, Shallow root development www.forestryimages.org orders. on compacted soils. Nutrient problems lowing or chlorosis of the leaves, inter- 10 Nutrient problems rarely kill veinal chlorosis, marginal necrosis and, plants outright, but proper nutri- in severe cases, total leaf necrosis. ent management is essential to op- Nutrient toxicities are less common in timizing growth and maintaining plants than nutrient deficiencies, but they high quality plants. Most nutri- can occur, particularly with some micro- ent problems are related to nutri- nutrients. With elements such as boron ent deficiencies, although nutrient or copper, the difference between suffi- toxicities may occur. ciency and toxicity is relatively small. The extent and nature of nutri- Caution should be taken when using mi- ent deficiencies can depend on sev- cronutrients in fertilization programs. If eral factors, including soil type or a soil test or foliar analysis indicates these media in production systems, site elements are needed, one strategy is to ap- conditions in the landscape and ply them as split applications to reduce the plant. Seventeen elements have the possibility of toxicity. Nutrient defi- been identified as essential for ciencies and toxicities need to be con- plant growth. Plants obtain car- firmed by a soil and leaf tissue analysis. bon, hydrogen and oxygen from Salinity is the concentration of water- air and water. The remaining ele- soluble salts in the soil or production ments are derived from the soil or media. These salts are necessary for from a fertilization program. All plant growth and development, but sol- of these are involved in one way or uble salt levels in high concentrations another with key physiological can cause toxicity problems. Typical functions in the plant. For exam- salts causing problems on plants are ple, nitrogen and sulfur are com- chlorides, sulfates and ammonium. Soil ponents of essential amino acids or media salinity is determined through Top: Chlorosis due to needed to build proteins. Magne- electrical conductivity measurements. nutrient deficiency. sium is a key element in chloro- The most effective way to alleviate the Middle: Manganese deficiency. phyll molecules, and iron is negative impact of high soluble salts is Bottom: Normal red involved in chlorophyll synthesis. through leaching. Leaching is effective maple leaves. In theory, any essential element in container production systems, but may be limiting for on field soils and in the landscape, the growth. As a practi- effectiveness of leaching depends on cal matter, only a soil drainage. handful of elements Soil pH refers to the acidity or alkalin- are commonly limit- ity of the soil. Soil pH influences the ing in field nursery availability of nutrients in the soil, the production and land- solubility of some nutrient elements and scape systems. In the the activity of soil microorganisms. It is upper Midwest, the generally accepted that the optimal pH most common ele- for plant growth and the availability of a mental deficiencies we broad spectrum of nutrients is between observe are nitrogen, 5.5 and 6.5 (slightly acid). As pH drops phosphorus, potassi- below or rises above this range, the solu- um, iron, magnesium bility/availability of some nutrient ele- and manganese. Iron ments may become limiting or toxic. and manganese defi- Iron and manganese are known to be ciencies are often limiting at soil pH levels above 7 (levels linked to specific above 7 are alkaline). Aluminum, man- plants and to alkaline ganese and copper can be toxic at soil pH soil. Nutrient defi- levels below 5.5 (strongly acid). Know- ciency symptoms in- ing the pH of soils and container media clude overall loss of is essential for maintaining adequate vigor, reduced shoot growth and development as well as for Nutrient deficiency on white pine. growth, general yel- diagnosing abiotic disorders. Herbicides Chemicals Herbicide injury symptoms vary with 11 Exposure to various chemicals can the plant and the herbicide applied. Un- cause either chronic or acute plant injury, derstanding the mode of action of her- depending on the type and duration of bicides and their effects on non-target the exposure. plants will aid in recognizing injury symptoms and distinguishing herbicide Salt injury injury from other abiotic and biotic Winter brings snow and ice and problems. Three widely used types of with them the need for deicing mate- herbicides are growth regulators, pho- rials. Salt used for deicing affects tosynthetic inhibitors and plant enzyme plants in the landscape when it accu- inhibitors. Growth regulatory herbi- mulates on stem tissue by airborne cides such as 2,4-D are plant hormones sprays and/or in soils because of run- that act by causing irregular growth. Salt injury off from treated areas. Soil buildup is Essentially, weeds grow themselves to on turf. especially a problem in landscape beds death. Symptoms of plant growth regu- adjacent to sidewalks or curbs where lator herbicides’ action on weeds include snow accumulates through plowing leaf cupping and twisted, distorted and shoveling. Deicing salts damage growth. These same symptoms are found plants through direct sodium chloride on non-target plants. Photosynthetic in- toxicity, dehydration due to osmotic hibitors such as atrazine and simazine act stress, reduced cold hardiness due to by interrupting normal photosynthesis. salt buildup on buds and stems, and/or These compounds block the mechanism its influence on soil nutrients. Salt in- that transforms sunlight into energy. jury usually expresses itself as termi- Photosynthesis inhibitors require sun- nal shoot dieback, bronze foliage on light to work. Injury symptoms, which evergreens, bleaching of ground cov- ers and turf, or total plant death in the case of ground covers and perennials. Successive years of dieback on woody trees and shrubs could result in a “witches’ broom” appearance on the outer branches. Given winter condi- tions, it is essential to deal with deic- ing in the landscape design phase. Deicing practices must be considered in plant selection and landscape bed Leaf cupping/ design in close proximity to paved curling due to a surfaces. If we are not fortunate to growth regulator herbicide. have an input on design and selection, we must intercept airborne salt through screening or apply more plant-friendly deicing materials such as calcium magnesium acetate.

Marginal chlorosis from herbicide injury.

Salt injury on taxus. Two examples of improper use of non-selective herbicide. appear on older leaves first, include leaf foliage. Injury symptoms include inter- 12 yellowing and interveinal chlorosis. veinal necrosis, marginal or tip necrosis, Plant enzyme inhibitors such as glypho- white or brown flecking or stippling on sate are translocated in the plant and act the leaf surface, and various degrees of on the enzymes that synthesize amino chlorosis. The extent of the injury is acids, protein and other plant com- very much dependent on other environ- pounds. Injury symptoms, including a mental and atmospheric conditions. yellowing and browning of leaves, do Factors include the type, concentration not appear immediately. Some herbi- and the length of exposure to the pol- cides will cause root swelling and stunt- lutant; the plant species, its stage of ed shoot growth. growth and physiological condition; If herbicide injury is suspected as a and atmospheric conditions – light, causal factor, identify the compound temperature, humidity and wind. applied, review its mode of action and Ozone is one of the more common determine its persistence in the soil. pollutants that can damage plants. This information will be useful in identi- Ozone is produced in the atmosphere fying proper treatment. Herbicide injury through a photochemical reaction be- produces many of the same symptoms tween volatile hydrocarbons and nitro- as nutrient deficiencies or toxicities. gen oxides in the presence of light. Nutrient deficiencies and toxicities can Ozone injury, if it is an issue, will gen- be eliminated as causes by leaf tissue erally occur in the summer, when tem- and soil analysis. peratures support reaction rates. Sulfur dioxide is another pollutant Pesticides that can injure plants. Sulfur dioxide Insecticides, fungicides and other emissions result from the burning of chemicals used in the control of plant coal and other petroleum products. pests can cause problems on both tar- Improved filtration technology and geted and non-targeted plants. Several emission controls have substantially re- factors can influence whether the pesti- duced sulfur dioxide injury. Isolated cide application is the solution or be- cases of volatile chemical spills or emis- comes part of the problem. sions may subject plants to injury. Such As with any chemical application, cases are usually easily diagnosed be- injury will depend on the type, concen- cause of the close proximity of the tration and application rate of the com- plants to the isolated event. pound; the plant species, its stage of growth and physiological condition; and atmospheric conditions – light, temperature, humidity and wind. Find- ing the perfect time to apply pesticides is always a challenge. Proper handling of the pesticides and close monitoring of weather conditions can avoid applica- tion-related injuries. Application inju- ries exhibit the same symptoms as nutri- ent disorders and other chemical appli- cations. In most instances, leaf chloro- sis, marginal and/or spotted necrosis, and total leaf necrosis are the visible symptoms.

Air pollution In some parts of the country, air pol- Ozone damage is sometimes evident lutants can cause acute or chronic injury as stippling or bleaching of needes in to plants. Air pollution impacts on conifers. Photo: Peter Kapitola, State Phytosanitary Administration, plants are most commonly found on the www.forestryimages.org Animal Damage and shrubs. Habitat reduction is the first line of defense against small rodents. 13 The issue of food supply and demand Unfortunately, many of our prized plant is a concern when we are investigating compositions also make for ideal cover. animal damage. When forage becomes Minimizing cover may deter feeding but limited, many of our ornamentals be- does not eliminate it. Caging plant come prime targets for deer, rabbits, crowns, wrapping wire mesh around the squirrels, mice and other rodents. Some bases of the plants, applying feeding re- ornamental species such as tulips, hostas pellents and using poison baits work rea- and taxus are preferred over natural for- sonably well. Quite often our best bet is age. Deer browse is obvious on taxus, to apply multiple methods in various com- arbovitae and other evergreens. Squirrels binations. When repellents are used, keep may feed on the petioles of newly ex- in mind that they degrade in winter panded leaves or gnaw on the upper sides weather and need to be reapplied through- of branches within tree canopies. Rab- out the season. Poison baits are often used bits, mice and other rodents focus on the for mice and should be positioned to avoid Deer browse. Minnesota Department of Natural ground-level portions of deciduous trees feeding by other animals. Resources Archives, Minnesota Department of Natural Resources, www.forestryimages.org Cultural Practices Cultural practices are designed to pro- mote and maintain plant growth and de- velopment. The same practices designed to promote plant health can at times be the cause of abiotic problems.

Planting process The planting process involves the pre- Squirrels foraging on the petioles of planting examination and evaluation of newly expanding leaves cause leaf the plant stock type (bare-root, container, drop in late spring/early summer. balled and burlapped [B&B], mechanical Mice damage. Robert L. Anderson, tree spade), the actual physical process of USDA Forest Service, planting and the follow-up maintenance. www.forestryimages.org Problems related to the planting process can originate within each of these. Con- sider the idiosyncrasies with each of the previously mentioned stock types, for ex- ample, the depth of the trunk/root collar on B&B trees, encircling roots in con- tainer-grown plants, root desiccation on Squirrel gnawing leads to extensive bare-root plants and glazing in mechani- stem decay. cal tree spade plantings. Each one of these factors can contribute to the suc- cess or failure of the plants. Improper handling and planting procedure con- tribute significantly to abiotic conse- quences, especially when they’re Rabbit browse often combined with soil or environmental looks like pruning cuts at the bases limitations at the planting site. Symp- of shrubs. toms related to poor planting procedures are similar to those of drought and flood- ing: shoot dieback, reduced leaf size, minimal shoot growth, root injury and poor root regeneration. If plant excava- Bark stripped by porcupines. tion is possible, examine the root system for white root tips and signs of root re- 14 generation. Under drought or water def- icits, white root tips will be absent, and existing roots will be dried and shriv- eled. Under excessive moisture and poor drainage, the root system will also lack white root tips and exhibit signs of an- aerobic conditions. The blackened outer surface of the roots will slough off, ex- posing inner gray and water-soaked, Mechanical injury stained tissue. In addition to the obvious Girdling roots on red oak. due to staking plant symptoms, evidence of twine practice. around the base of the trunk, scars from production and landscape systems. Encir- staking or other signs of mechanical in- cling roots due to production methods, jury may lead to conclusions on the caus- poor soil conditions, excessive mulch and al factors and required treatment. narrow planting sites have contributed in Problems caused by poor planting pro- one form or another to the problem. A cedures can be due to marginal plant distinction is sometimes made between stock quality; poor soil ball or container two forms of girdling roots. "Girdling media moisture prior to planting or roots" refers to the condition that occurs during establishment; improper plant- when roots encircle upon themselves. ing depth, either too high or too low; Stem-girdling roots encircle the tree compacted planting sites and poor drain- stem above the trunk/root collar. Both age through the soil profile; improper of these conditions affect the structural irrigation scheduling following planting; stability and anchoring of the plant and and improper mulching practices. restrict the roots system's ability to ade- quately mine the soils. Stem-girdling Girdling roots roots compress the conductive tissue in Crown dieback Girdling roots have long been recog- the trunk, restricting translocation and due to improper nized as an abiotic problem in both eventually leading to trunk decay. Each planting technique. situation causes a slow but progressive decline in plant performance. Treatment for girdling and stem-girdling roots con- sists of the selective removal of root sec- tions. The extent of the removal varies with the condition and the length of time that the plant has been in place. Root removal may span several seasons to minimize stress to the plant. To elim- inate or reduce the incidence of this problem, use proper planting procedure Polytwine left on a B&B tree. and long-term mulching practices. At planting, encircling roots should be cut or removed to ensure proper movement of new and existing roots into the sur- rounding soils. Excessive mulch layers around the bases of plants cause new roots to work their way upward to capi- talize on optimal aeration, moisture and nutrient levels. Roots remain in the mulch layers and encircle as continued mulching maintains the preferred envi- ronment. Mulch layers should be re- Plastic wrap and poly twine on a moved periodically and problem roots B&B shrub. cut and redirected. Mulch practice expansion, shoot expansion and root 15 The well-documented benefits of initiation require water at fairly regular mulch support its widespread use. intervals. Once plants are established, Mulch conserves soil moisture, reduc- however, irrigation can be adjusted ac- es soil erosion, minimizes weed cordingly. Abiotic problems related to growth, moderates soil temperatures irrigation operation can be due to and contributes to soil fertility follow- moisture deficits resulting from im- ing decomposition. However, abiotic proper scheduling and delivery or to disorders can result from its improper flooding due to the failure of valves to or overuse. Excessive mulch and im- shut off appropriately. Problems can proper application lead to crown decay be avoided by periodic checks to ensure and plant decline. Problems associat- that the system is operating correctly ed with improper mulching include and delivery is appropriate for the excessive moisture buildup on trunk plant, season and soil type. collars and trunk decay, negative im- Broken irrigation pacts on rooting depth, promotion of emitter on girdling roots, and nitrogen deficien- street tree. cies in ground covers and annuals Summary plantings. One of the best strategies for dealing with abiotic disorders is to be proac- Irrigation management tive. Several routine planning and Proper installation and operation of management practices can aid in either irrigation systems is essential for effec- minimizing their occurrence and im- tive and productive plant growth and de- pact on plants or assisting in their velopment. Proper timing, frequency timely diagnosis and treatment. and rate of application not only ensure plant health and vigor but also provide Plant selection for the efficient use of water resources. Select plants that are reliably hardy Supplemental irrigation is necessary in your area. Remember that hardiness during plant establishment. Demands zones are based on long-term records of for water during leaf emergence and average low temperatures. Even species that are hardy for your zone may be damaged in an extremely cold winter or by fluctuations early or late in the winter. Match species to site environ- mental and soil conditions. In addition, employ best manage- ment practices in producing, planting and managing the plants, whether they are in production or landscape systems.

Excessive wetness on trunk Environmental conditions due to mulch buildup. Perform a thorough analysis of the site conditions. Site analysis includes identifying seasonal light and wind pat- terns, noting microclimatic variation on the site and recording site irregularities that could influence the way water moves on or off the site. Document the characteristics of sur- rounding properties and identify po- tential influences from these areas. Have access to regional and local Maladjusted irrigation head. weather data. Soil conditions Resources 16 Know your soils and keep records of Develop a reference library for easy soil physical and chemical properties. Es- access to books and periodicals. Main- tablish baseline data on soil nutrient and tain an up-to-date list of Internet sites pH levels. In production systems, devel- related to diagnosing plant problems op a routine schedule of soil testing. and treatment recommendations. Here are some references to aid in diagnosing Water quality abiotic plant problems. Water quality can dramatically affect • Plant Health Care for Woody nursery crops, especially in container Ornamentals. 1997. International production. Buy and learn how to use Society of Arboriculture, Savoy, Ill.: water quality monitoring equipment to Cooperative Extension Service, check your pH and electrical conduc- College of Agricultural, Consumer, and tivity. If you are using multiple water Environmental Science, University of sources, be sure to have each source Illinois, Urbana-Champaign. tested for alkalinity, calcium/magne- sium ratio, soluble salts and sodium. • Costello, L.R., et al. 2003. Abiotic Disorders of Landscape Irrigation management Plants. Pub. 3420. Overirrigating wastes water and University of California. money and can cause as many plant Oakland, Calif. problems as too little water. Consult with local Extension personnel and oth- Other publications er experts in your area to develop a wa- • E2839: Pocket IPM Guide for ter management plan that supplies ade- Woody Ornamental/Landscape quate water without overapplying. Be Plants, 128pp., $15; sure to maintain and check irrigation • E2982: Pocket IPM Guide for Weed equipment regularly. Identification in Nurseries and Landscapes, 176 pp., $19. Nutrition management Available from your county Extension Poor nutrition can reduce plant health office or the MSU Bulletin Office: and vigor even in the absence of visible www.emdc.msue.msu.edu deficiency symptoms. Proactive nutrition management can help to reduce the pen- dulum swings of fertilizing only when Nevertheless, weather extremes and plants become symptomatic. Follow the other factors causing abiotic disorders are old adage “Test, don’t guess." Soil and fo- a fact of life. We don’t need to feel com- liar nutrient testing should be key compo- pletely at the mercy of Mother Nature, nents of a nutrient management plan as however. By selecting the right plants, well as an aid in troubleshooting. performing thorough planning exercises and maintaining proper management Management records techniques, we can eliminate or reduce Keep records on all site visits and man- the impact of abiotic factors on our pro- agement operations. duction or landscape systems.

Photographs by Robert Schutzki and Bert Cregg, except as noted. Graphic design by Marlene Cameron.

MSU is an affirmative-action, equal-opportunity institution. Michigan State University Extension programs and materials are open to all without regard to race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, marital status, or family status. • Issued in furtherance of Extension work in agriculture and home economics, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Thomas G. Coon, Extension director, Michigan State University, E. Lansing, MI 48824. • This information is for educational purposes only. References to commercial products or trade names do not imply endorse- ment by MSU Extension or bias against those not mentioned. This bulletin becomes public property upon publication and may be printed verbatim with credit to MSU. Reprinting cannot be used to endorse or advertise a commercial product or company.