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Abiotic Disorders of Landscape Plants Biotic vs. Abiotic = Living vs. Nonliving Left – lacebug damage vs. Other three – herbicide damage Causes of Tree Disorders Biotic Abiotic Insects, Mites Fungi, Bacteria Viruses Environment Nematodes Parasitic Plants Physical or Mechanical Factors Other Plants Chemical Agents (competition, allelopathy) Rodents, Birds Other Animals People Characteristics of Biotic vs. Abiotic Biotic Abiotic Physical evidence – insect cast skin, fungal spores Progressive spread on a tree or to other trees Species affected may be limited Generally no physical evidence May or may not progressively develop or spread to other trees More likely to affect many or all plants Biotic – rodent feeding vs. Abiotic – Weed eater damage? Primary vs. Secondary Causes of Disorders Abiotic factors and agents (alone or in combination) may weaken or stress trees, predisposing or increasing their susceptibility to biotic agents. If the abiotic factor or agent is the main problem it is called the primary cause of the disorder, with the biotic agent being the secondary cause of the disorder. Environmental Causes – The Main Three Water Light Temperature Causes can overlap and confound – hot and dry, dry and windy, etc. Water Soil Quantity – too much, too little, affect on air in soil Quality – pH, salinity, contaminants Atmospheric Humidity Acid rain damage Snow, ice, hail, etc. Water Extreme Effects Wilt (too much or too little) Necrosis (too much or too little) Shed/split parts (mainly if too little) Poor growth (too much or too little) Odd growth (mainly if too much - hypertrophied lenticels, roots on stems) Drought responses http://warnell.forestry.uga.edu/warnell/s ervice/library/index.php3?docID=165 Shedding parts – leaves, bark, buds, fruit Water – Processes Affected Nutrient uptake Photosynthesis Transpiration Translocation Growth, cell turgor Seed germination Eastern white pines atop the berm receive just the right amount of water whereas the pine – planted at the same time, same size – is declining because of too much water collecting around it at the base of the berm. Light Quantity - Shade (no direct sun) - Part shade/sun – less than 6 hours of direct light - Sun – at least 6 hours of direct light Live oaks (evergreen trees) should be grown in full sun. How is this tree supposed to get enough light (or water)? Competition for light, water, space with other plants and humans! Light – Processes Affected Photosynthesis and respiration Hormone production and movement/use Phytochrome and flowering Light Effects Sunburn – marginal leaf necrosis, bark discolor/cracking/peeling, flowers look water soaked Sunscald (light combined with fluctuations in temperature) - winter bark injury (also called frost cracks) Size – exterior leaves larger than interior leaves Temperature Air Extremes – hot and cold - when they occur (after harden off in fall vs. after break dormancy in spring) - how long they last – short term vs. sustained - how extreme – does the water in cells have time to freeze, or leaf margins burn? - affects photosynthesis, respiration, transpiration, dormancy, flowering, fruit set Heat problems could come directly from the sun or indirectly from expansive paved or building areas. Temperature Soil Extremes – hot and cold - roots are less cold hardy than stems (trees in containers more vulnerable) - hot, unmulched soil may lead to death of surface roots - affects growth, nutrient uptake, seed dormancy and germination Temperature – Processes Affected Photosynthesis Transpiration Growth Seed germination Dormancy Dura-Heat Heritage Environmental Causes – Others Wind/Air Movement (speed, direction) - Physical damage - Carrying pollutants (gases, dust, salt) Nutrient availability - Deficiencies - Excesses Winds from Hurricane Isabel blew over many large, old trees, but other factors, such as moist soil and root cutting, contributed to their demise. Environmental Causes – Others Topography - warm air rises/cold settles (affects frost areas) Lightning Fire Physical or Mechanical Agents Soil compaction Tree production methods (bareroot, B&B, containers) Improper planting Improper maintenance (mulching, pruning, fertilization, irrigation) Nursery to Home issues Proper depth of roots within a harvested root ball - “The continuum” of main order root depth - liner production (seedling/grafted) - field or container production - landscape installation - landscape maintenance “Too deep” from the nursery Field Production & Container Production Seedlings planted too deep because root flare hard to detect Seedlings planted too deep to prevent them from blowing over Substrate settling and long narrow seedling containers Buds/grafts planted too deep to bury the graft union (or seedling cut back “dog leg”) Seedlings end up too deep due to cultivation for weed control Bare root trees ‘Dogleg graft unions’ Physical or Mechanical Agents Root cutting Damage from equipment Construction damage Infrastructure (buildings, roads, walls, sidewalks, pipes, gravestones) Chemical Agents Pesticides Herbicides/soil sterilants Salt (aerial and deicing) Excess/shortage of nutrients (fertilizer) pH problems Contact vs systemic Chemical Agents Air pollutants Other phytotoxic chemicals (gas, solvents, etc.) Ozone Diagnostic Challenges Many biotic and abiotic agents can cause injury to trees Landscapes exhibit tremendous variability (species, soils, etc.) Tree problems can have multiple factors, causes, or causal agents Chronic problems may express subtle symptoms Steps for Diagnosing Tree Disorders 1. Identify the tree correctly Heart-shaped leaf – katsura, linden, redbud? Steps for Diagnosing Tree Disorders 2. Identify the symptoms Tree missing part of its root flare. Leaf Symptoms Wilt Necrosis Chlorosis Ragged edges Malformed Defoliating Early fall color/senescence Shoot Symptoms Wilt Dieback Distortion Witches’ Broom Branch and Trunk Symptoms Sunken, discolored bark Woundwood Bark shred/shed Bleeding Swelling Splitting and cracking Root Disease Drought Root Symptoms Shriveled Discolored Distorted How many things can you find wrong with the tree/shrub planting on this lot?
