What’s Wrong With Your Plants and Why? Biotic vs. Abiotic Problems Plants can be injured and damaged by biotic (living) and abiotic (non-living) agents. Based solely on symptoms, however, determining whether the condition is caused by a biotic or an abiotic agent can be challenging. In many cases, a proper diagnosis of abiotic diseases requires thorough examination of the site, knowledge of relevant past and present environmental conditions, in-depth knowledge of plant species biology, site management history, and an orderly series of tests to determine possible causes. I’ll discuss some general characteristics that can help to differentiate between biotic and abiotic stresses. Tony Glover Regional Extension Agent

Diagnosis Can Be Tricky Without All The Facts

Abiotic vs. Biotic Problems Abiotic – non-living agent (non-infectious). Extreme temperatures Excess or deficient water, light or nutrients Soil compaction, soil grade changes Damage from cultural practices: herbicides, fertilizers, pruning, mulching Abiotic agents or factors include environmental conditions such as extreme temperatures; excess or deficient water, light or nutrients; soil compaction; and abnormal conditions such as drought, flooding and/or adverse cultural practices. Most abiotic diseases cause generalized symptoms such as wilting, yellowing, thinning and the development of smaller than normal leaves, limited root growth or slow growth.

Abiotic vs. Biotic Problems Biotic – living agent (infectious). Pathogens - parasitic microorganisms that cause disease (fungi, bacteria, viruses, phytoplasma) Pests – insects, mites, nematodes or mammals feeding on or damaging plants. Abiotic agents or factors include environmental conditions such as extreme temperatures; excess or deficient water, light or nutrients; soil compaction; and abnormal conditions such as drought, flooding and/or adverse cultural practices.

Abiotic vs. Biotic Problems Symptom Progression Biotic disease – symptoms progress and nearby plants become infected. Abiotic disease – generally a lack of symptom progression. Does not spread. Exception – nutritional deficiency symptoms progress slowly. The progression of symptoms is one of the most important characteristics associated with problems caused by biotic or living agents. Diseases often exhibit both primary and secondary symptom. For example, decayed tree roots primary symptom and yellowing leaves due to damaged roots are secondary symptom. Secondary invaders in later stage of disease can also complicate diagnosis. Look for lack of symptom progression with abiotic diseases. For example, in the case of herbicide damage, initial symptoms of 2,4-D injury include leaf deformation may initially be similar to infectious agent like a virus. However, herbicide injury the symptoms appear suddenly and new leaves may be free of symptoms indicating a lack of progression Abiotic disease – Herbicide Injury

What’s Wrong? Biotic or Abiotic Diseases are the exception, rather than the rule. Because diseases are difficult to diagnose it is often faster to rule out the involvement of other factors than to verify the presence of disease. It is important to rule out the possibility of abiotic disease problems and one of the best times to do this is during the site visit. Ruling out abiotic problems can be challenging. But where do you start? What’s Wrong? Biotic or Abiotic

Steps in Problem Diagnosis Know the Plant Inspect the Site and Look for Patterns Look for Symptoms or Signs Examine cultural practices and weather conditions Identify Potential Causes Consult Resources and Reach Diagnosis

Steps in Problem Diagnosis Know the Plant Identify the species and cultivar affected Know what problems commonly affect the species. For example: Red Maple – Phyllosticta Leaf Spot, gloomy scale Flowering Dogwood – Powdery Mildew, spot anthracnose

Steps in Problem Diagnosis Know the Plant What’s normal for specific plant? Fall Needle Drop on White Pine

Steps in Problem Diagnosis Know the Plant Look at the Whole Plant (foliage, stems, branches, leaves, and roots) Note the color, size, and thickness of the foliage Check the trunk and branches Examine the Roots

Check the Trunk and Branches Look for wounds, cankers, exit holes and other clues Pitch Tubes on Bark, Southern Pine Beetle

Check the Trunk and Branches Sapsucker damage to sugar maple Don’t mistake sapsucker damage for borer exit holes

Check the Trunk and Branches But…

Girdling Roots

Girdling Injury

Planted too deep

Deep Planting or Covered Later Check for flare at base of trunk

Girdling Roots Girdling roots are a common problem with trees that are planted too deep

Too Much Mulch Over The Root Ball Problems caused by too much mulch Keeps trunk tissue wet Can increase rodent damage Mulch can intercept rain and irrigation Can keep poorly drained soils too wet Can encourage surface roots Can encourage development of stem girdling roots Too much mulch was placed over the root ball. This keeps trunk tissue wet, can increase rodent damage on the buried portion of the trunk, can intercept rain and irrigation meant for the roots, can keep poorly drained soils too wet, can encourage surface roots, and can encourage development of stem girdling roots.

Planted too deep Old root system has died

Steps in Problem Diagnosis Inspect the Site and Look For Patterns Determine prevalence of problem. Large area, all plants – generally abiotic. Scattered, localized – generally biotic. Check for distribution of symptoms. Uniform – generally abiotic. Random – generally biotic. Are the symptoms/patterns related to geography? (soil, low spot, etc) Is the damage limited to one type of plant? Multiple plant species - often abiotic One species – often biotic

Observation of Field Patterns Abiotic Problem Symptoms distributed in a large area. Damage pattern is uniform. Gas leak from building

Observation of Patterns Random vs. Uniform Leaf Spot (Fungal) Marginal Leaf Scorch

Observation of Field Patterns Random vs. Uniform Boxwood Phytophthora Root Rot Oak Nutrient Deficiency

Observation of Field Patterns Random vs. Uniform Random Patches Uniform Stripes Bermuda spring dead spot Fertilizer application problems

Steps in Problem Diagnosis Know the Plant Inspect the Site and Look for Patterns Look for Symptoms and/or Signs Examine Cultural Practices and Weather Conditions Identify Potential Causes Consult Resources and Reach Diagnosis Examine injured parts and list the symptoms. Is injured part chlorotic, necrotic, discolored or distorted? Are the symptoms in patches, yellowing, leaf spots?

Look for Symptoms and/or Signs Symptoms - plant reactions or alterations of a plant’s appearance due to a disease or disorder. Signs - actual presence of the pathogen, it’s parts or by-products seen on a diseased host plant.

Symptoms

Signs Visible or physical presence of a pathogen or pest. Signs - visible presence of the pathogen, it’s parts or by-products seen on a diseased host plant

Steps in Problem Diagnosis Know the Plant Inspect the Site and Look for Patterns Look for Symptoms and/or Signs Examine Cultural Practices and Weather Conditions Identify Potential Causes Consult Resources and Reach Diagnosis Examine injured parts and list the symptoms. Is injured part chlorotic, necrotic, discolored or distorted? Are the symptoms in patches, yellowing, leaf spots?

Steps in Problem Diagnosis Examine Cultural Practices and Weather Conditions Ask questions - Collect as much background information as possible When was the problem noticed? Was the damage sudden or gradual? Has the problem spread? How old are affected plants? What cultural practices have been performed recently? Herbicide Sprays?

Hail Damage

Steps in Problem Diagnosis Identify Potential Causes Consult Resources and Reach Diagnosis Get Laboratory Assistance Take samples (plant, soil) Don’t forget pictures Synthesize Information and Identify potential causes When you have finished collecting information about the turfgrass and site, identify potential causes. Test likely causes and consult resources. Submit samples to agricultural or plant disease lab, soils labs; use literature and resources to reach diagnosis.

Most Common Diseases of 2009 Ornamentals Phytophthora Root and Crown Rot Boxwood, Juniper, Hydangea, Leyland Cypress, Pansy, Petunia, Fungal Leaf Spots (Oak Leaf Blister, Anthracnose, and other leaf spots) Armillaria Root Rot Oakleaf Hydrangea, Cotoneaster Pythium Root Rot Pansy and other flowers Powdery Mildew Dogwood, Crape Myrtle, Rose Botryosphaeria Canker /Dieback Leyland Cypress, Japanese Maple, Cleyera Bacterial Leaf Spots Basil, Begonia, Oakleaf Hydrangea, English Ivy Azalea Leaf Gall Sooty Mold Various Trees and Shrubs (Hackberry Woolly Aphid)

Diseases Caused by Phytophthora Some of the most economically important and damaging diseases on woody plants in the Southeast, USA, and worldwide The name Phytophthora derives from Greek and literally means “plant destroyer.” Cause problems annually Notorious Phytophthora diseases include rhododendron root rot, sudden oak death, and potato late blight. Particularly serious in or following “wet” years Diseases often are associated with wet or saturated soils

Phytophthora 101 Phytophthora species resemble fungi but are not. They are most closely related to aquatic organisms, such as brown algae and diatoms. Phytophthora organisms are often referred to as ‘water molds’ because they do need water to complete their life cycle. This group of organisms produces swimming spores .

Disease Cycle: Phytophthora Root Rot

Some Trees and Shrubs Attacked Abies – fir Acer – maple Arbutus – madrone Betula – birch Buxus – boxwood Camellia – C. japonica Castanea – chestnut Cedrus – cedar Cercis – redbud Chamaecyparis - false cypress Citrus - orange, lemon, etc. Cornus – dogwood Cryptomeria -Japanese cedar Cupressus - cypress Elaeagnus Eucalyptus Fagus – beech Ficus - fig Forsythia Ilex - holly Juglans—walnut Juniperus –juniper Kalmia – laurel Malus - apple

More Trees & Shrubs Attacked... Pieris – andromeda Pinus – pine Platanus – sycamore Prunus - cherry, plum, etc. Pseudotsuga - Douglas fir Pyrus - pear Quercus – oak Rhododendron - rhododendron, azalea Robinia – locust Rosa - rose Rubus - raspberry Syringa - lilac Taxus - yew Thuja - arborvitae Tsuga - hemlock Vaccinium - blueberry Viburnum -arrowwood Ulmus – elm

Phytophthora as Pathogens of Woody Plants They can attack all parts of the plant Blight & dieback on shoots & foliage —uncommon Cankers on stems & trunk —e.g., “bleeding” cankers – occasionally Root & crown rots — most common

Symptoms—Above Ground Appear after roots are diseased Chlorosis & yellowing of the foliage very slight at first, then becoming obvious Stunted growth Overall wilting & decline Cankers - orange/red/brown discoloration on stems and trunk distinct margin between healthy & diseased tissues Plant death

Phytophthora Foliage Blight

Trunk and Stem Cankers “bleeding” cankers - maple

Trunk and Stem Cankers “bleeding” cankers - Oak Slide 28. The next few slides show what P. ramorum cankers look like compared to cankers caused by other fungi or insects. On the left is a photo of the outer bark, showing the bleeding canker caused by P. ramorum. On the right is the same tree with the outer bark removed to reveal the inner bark under the bleeding. outer bark inner bark Photo: Bruce Moltzen, Missouri Department of Conservation

Symptoms—Below Ground Must expose roots for examination this usually requires digging! need to know what healthy roots look like! Reduced root volume/lack of feeder roots Roots discolored - red, brown, dark brown healthy roots are white or off-white Cortex sloughing/root rot Cankers on root crown may move up stem above ground

Boxwood - Cortex sloughing/root rot

Phytophthora Root Rot on Boxwood

Phytophthora Root Rot on Shore Juniper

Field Diagnosis Above-ground symptoms alone usually are not diagnostic—merely indicate vascular dysfunction Therefore, look below ground at roots & crown Together, these may be diagnostic Other pathogens also can cause root rot Armillaria, Fusarium, Sclerotium, Thielaviopsis, etc. and sometimes Pythium spp., especially on boxwood

Fungal Leaf Spot Diseases Typically have tan to gray centers surrounded by a darker border Fungal fruiting structures (pycnidia, spores, etc.) can be seen within the leaf spot Defoliation is common Fungi survive on fallen leaves Prolonged leaf wetness, high humidity and poor air circulation increase disease development Spores are spread by wind and water-splashing, but can also be spread by insects, on clothes, tools, and hands

Japanese Maple Phyllosticta Leaf Spot

Defoliation due to Entomosporium leaf spot disease - Indian Hawthorn Less water stays on this protected area

Oak Leaf Blister Common fungal disease on oaks, especially red oaks (s. red and water oak) Disease favored by cool, wet springs Symptoms appear in late spring as yellow, blister­like, circular, raised areas

Oak Leaf Blister Spots become dull brown with age As leaves mature, become resistant to infection Affects appearance not tree health Fungicides not needed, but one application of chlorothalonil or mancozeb before budbreak will control disease

Anthracnose - Red Maple

Cercospora Leaf Spot – Crape Myrtle

Cercospora Leaf Spot

Cercospora Leaf Spot - Dogwood

Boston Ivy Leaf Spot The fungus Guignardia bidwellii f. sp. parthenocissi causes distinct, angular, tan, spots to form on Boston ivy leaves in the spring and summer. A dark brown halo or margin along the edge of the spot is usually present. Within the tan areas, small black dots (fungal fruiting structures where new spores develop) can be observed soon after the spot reaches full size. Branch dieback occurs if the disease is very severe.

Armillaria Root Rot

Armillaria Root Rot – Oakleaf Hydrangea

Armillaria Root Rot - Oakleaf Hydrangea

Armillaria Root Rot -Oak

Armillaria Root Rot - Rose White fungal growth under bark Drainage? Irrigation? Death by watering hose? No fungicides for control Resistant plants best replacement option

Bacterial Leaf Spots Plant wetness, high humidity and warmer temperatures favor disease development Bacterial cells spread by water splashing, tools, hands, or insects No Fruiting structures in spots Many controlled with copper fungicides (Kocide) Oak Leaf Hydrangea Angular leaf spots running along veins

Bacterial Leaf Spots ‘water soaked spots’ English Ivy Hydrangea

Sooty Mold Common name for group of black-colored fungi that grow on honeydew on plants and other surfaces Fungal growth gives appearance of being covered with a layer of soot Honeydew produced by aphids, mealybugs, soft scales, whiteflies Control sooty molds by controlling the honeydew producing insect. Drenches with Merit or Safari for hackberry aphids (early spring) Sooty mold on crape myrtle

Asian Woolly Hackberry Aphid Multicolored Asian lady beetle pupa

Azalea Leaf Gall Occurs in cool, moist springs Spores for next year’s infection are released when leaf galls turn white Prune infected leaves Leaves, and occasionally flower buds, become deformed, developing pink or white, soft fleshy growths called galls.

Camellia Leaf Gall Leaves, and occasionally flower buds, become deformed, developing pink or white, soft fleshy growths called galls. Spores for next year’s infection are released when backside of leaves turn white Camellia leaf gall early symptoms and last year’s infected leaves

Leaf Gall Control Remove galls and destroy before they turn white with spores Disease most severe when foliage becomes wet during leaf expansion in spring. Avoid planting in heavy shade Avoid wetting foliage in spring If the disease was severe in previous years and galls were too numerous to pick, apply a fungicide before new leaves and flowers emerge. Applications can stop when leaves become full size Bayleton. Apply first spray as new leaves and flowers appear. Repeat 2-3 times at 10-day intervals. Problem: Some leaves have red or yellow spots. Other leaves, and occasionally flower buds, become deformed, developing pink or white, soft fleshy growths called galls. Remove galls by hand. Apply first spray as new leaves appear. Repeat 2-3 times at 10-day intervals. Plant Azaleas resistant to leaf gall

Powdery Mildew Common disease on dogwood and other plants Looks like baby powder Use Resistant Cultivars: Cherokee Brave, Karen’s Appl. Blush, Kay’s Appl. Mist, Jean’s Appl. Snow Start sprays at first sign of disease (early May) Fungicides: Heritage Spectricide Immunox Fertilome Systemic Fungicide Fertilome Halt Systemic Fungicide Powdery mildew will reduce growth Once leaves are white fungicides are of little value

Too late for fungicides

Spot Anthracnose Small reddish spots on bracts and leaves, trees in sun Rake leaves in fall Heritage, Daconil, Mancozeb, Halt, Immunox Spray before budbreak, after bract fall, and one month later, and September after new flower buds form Heritage, Daconil, Dithane/Protect, 3336, Eagle Heritage, Daconil, Dithane/Protect, 3336, Eagle

Dogwood Anthracnose Different disease than spot anthracnose Spots with reddish or purple borders Spots enlarge over time Leaf, twig blights, cankers, can kill tree Blighted leaves remain attached through winter Resistant Cultivar ‘Appalachian Spring’

Hydrangea – Leaf Spot Several fungi cause leaf spots on hydrangea – Cercospora, Corynespora, Colletotrichum Often in combination with powdery mildew Adequate plant spacing for good air circulation Avoid watering late in the day Remove fallen leaves Apply fungicide at first sign of disease: Heritage, Daconil*, Immunox Mancozeb*, Fertilome Systemic Fungicide * Poor control of powdery mildew, but good leaf spot control Ultra-fine Spray Oil

Leyland Cypress Problems

Botryosphaeria Canker J. Woodward - UGA

Botryosphaeria Canker UGA J. L. Williams-Woodward - UGA

Control of Canker Diseases Difficult to control once infection has occurred Prevent canker diseases by proper establishment and care: Plant in well drained soils adequate plant spacing Irrigate plants to prevent drought stress, mulch plants Remove branches with cankers. Trace the dead wood back to the base of the canker and prune at bud or branch fork. Prune 4-6 inches below canker. Sterilize pruning tools frequently Avoid canker susceptible plants Fungicides are of little value

Thank You