Appendix C. Diagnostic Tables

Dollar spot

Develops when soil temperatures decline to 70°F in the fall, but the symptoms do not necessarily appear at this time. Symptoms are most evident during periods of cool, wet weather in the fall and spring. Symptoms are typically large circular patches of brown or tan turf. Each patch sometimes has a reddish ring. Sheath lesions are typical. Affects all warm-season turfgrasses.

Bermudagrass rarely sustains significant damage and grows out of the symptoms quickly when the disease does occur. In contrast, centipedegrass, seashore paspalum, St. Augustinegrass, and zoysiagrass often sustain serious damage and recovery can take several weeks or months. Do not apply nitrogen to warm-season grasses in the fall and spring. Avoid establishing these grasses in low-lying areas that remain saturated for extended periods of time.

Only affects bermudagrass and zoysiagrass. Symptoms appear in circular patches from 6 inches to several feet in diameter that remain dormant as the turf greens up in the spring. These patches eventually die and collapse to the soil surface. The roots, stolons, and rhizomes are dark and rotten in affected areas. Patches recur in the same spot each year and increase in size by up to several inches each season.

Spring dead spot

Do not apply nitrogen within six weeks of winter dormancy. Reduce thatch buildup and relieve soil compaction through aggressive aerification and vertical mowing. Affected areas should be hollow-tine aerified at least three times per year during the summer when these grasses are most actively growing. Once the symptoms appear, the only means of control is to encourage the spread of the turf into the affected patches. Frequent spiking or aerification is recommended to break up the mat of dead turf in affected patches. Preemergent herbicides such as DNA herbicides will slow recovery significantly and should not be used in sites with history of this disease.

Early symptoms include small, yellow flecks that develop on the leaves and stems. The flecks expand over time into raised pustules, orange or red in color, that rupture to release powdery masses of yellow, orange, or red spores. Infected plants become yellow and are more susceptible to environmental stress. Heavily infected areas become thin and exhibit clouds of orange dust (rust spores) when the foliage is disturbed. The rust pustules on infected leaves turn black during the fall in preparation for overwintering. Primarily affects Kentucky bluegrass, tall fescue, St. Augustinegrass, and zoysiagrass.

Rust

Plant rust-resistant turfgrass varieties whenever possible to reduce injury. When planting cool-season turfs, use blends and mixtures of multiple species and/or varieties whenever possible. Plant shade-tolerant grasses, and raise mowing heights in heavily shaded areas. Prune trees and remove unwanted undergrowth to improve air movement and reduce prolonged leaf wetness. Mow at recommended heights and on a regular basis, removing no more than 30% to 40% of the foliage in one mowing. Collect and dispose of clippings from infected areas to slow the spread of the disease. Fertilize to meet the nutritional needs of the turf.

Large rings or arcs of dead or very green grass are bordered by zones of darker green grass; mushrooms may be present. This disease is more common on droughty sites and poorly nourished turf and occurs on all turf cultivars year-round.

Fairy ring

Aerate turf frequently. Maintain adequate nitrogen fertility. Irrigate during dry periods.

Circular straw-colored patches range from 3 inches to 12 inches in diameter. Patches occur in bluegrass and fine fescue lawns two years or older, July to September.

Summer patch

Avoid excessive nitrogen, especially in spring, and use slow-release nitrogen sources. Increase mowing height. Avoid light, frequent watering. Reduce thatch buildup.

Turf comes up easily and obviously lacks roots. Turf can sometimes be rolled up like a carpet. Infestations can be severe on bluegrass, ryegrass, and fine fescues.

White grubs; C-shaped grubs found in soil usually in spring and fall

Avoid excessive irrigation and fertilization, particularly organic fertilizers, when adults are active (June through July). If necessary, use a labeled insecticide to target early instars in midsummer to late summer.

Turf blades can be pulled easily from sod. Light tan, sawdust-like pockets can be detected in soil in damaged areas.

Hunting billbugs; small, white, legless grubs found near crowns and roots; majority active from June through August but can be found in soil all year

Water and fertilize grass to stimulate regrowth if damage occurs. If necessary, use a labeled insecticide to control adults in April to mid-May; a second application may be required in mid to late June.

Defined “edge” or border can be detected between damaged and healthy turf (armyworm).

Irregular brown patches occur with white moths flying over the turf (sod webworms).

Caterpillars (armyworms, cutworms, and sod webworms); light brown banded caterpillars may be found at soil surface feeding on blades (armyworms) or in the thatch (cutworms, sod webworms), active July through Sept. (armyworm), June through Aug. (sod webworms), and April through May (cutworms)

Bermudagrass can regenerate within a few days with adequate irrigation. Newly-established turfgrass may require reseeding (armyworm). High-cut turf rarely shows signs of sod webworm or cutworm damage. Both turf types outgrow feeding damage in spring (sod webworm or cutworm) and fall (sod webworm).

Irregular or circular patches occur in open turfgrass; damage increases in size from year to year. Turf struggles to recover, and area may become infested with weeds.

Ground pearls: tiny white shell (“pearl”) or small (0.06 inch) pink-orange scale with well-developed claws

Promoting healthy turf growth using adequate fertility and irrigation practices can mask symptoms of ground pearl damage. Reseeding or sodding is not effective. Some zoysiagrass cultivars are resistant.

Large mounds (less than18 inches in diameter) are created from excavated soil in open areas.

Fire ants, medium-sized (1/16 inch to 1/4 inch) red and black ants; active spring-fall

In heavily-infested areas, chemical treatment may be necessary. Mound treatments can involve drench method (high traffic areas) or the use of bait stations. Avoid moisture for 24 hours after positioning bait stations or product will turn rancid.

Localized yellow or brown areas can be detected during dry weather. Damage usually occurs in sunny, well-drained locations.

Chinch bugs, tiny black insects with shiny white wings found on crowns and stems

Generally only an issue in St. Augustine grass, and often controlled by natural predators such as big-eyed bugs. Use low to moderate rates of nitrogen when fertilizing, and clean equipment if moving from lawn to lawn.

Straw-colored patches are surrounded by a ring of dark green turf.

Animal urine; may resemble some diseases; may kill the crown tissue

Heavy irrigation will promote recovery of spots by leaching salts from the soil.

Banded streaks or irregular patterns occur. Grass may appear to be stimulated at the margins with dark green and fast-growing areas.

Fertilizer or chemical injury; may kill the crown tissue

Calibrate spreaders and sprayers for uniform and accurate application of materials.

Black or dark spots or patches occur on lawn.

Oil or gasoline damage from leaking lawnmower

Severe oil leak or spill requires removal of affected soil. Small gasoline leaks or spills volatilize quickly.

Large yellow area occurs near a swimming pool.

Chlorine damage from pool water

Leach chlorine through soil with water and replant.

Scalped grass occurs over high spots, and crowns of plants are exposed.

Mower injury

Level the terrain, and raise mower blade or change mowing direction.

Shredded blade tips can be detected. Tips appear gray and then turn tan.

Dull mower injury

Sharpen mower blades.

Patches of dead or dormant grass occur, often following a dry period.

Buried debris, insect injury, or thick thatch

Check for causes.

Turf is pale-green to golden-yellow. Yellow streaks may form parallel to leaf veins.

Chlorosis; iron or nitrogen deficiency

Maintain adequate fertilizer levels.

Black or greenish crust is visible on bare soil or in thin turf. Crust occurs in poorly drained or compacted areas and is usually more severe in shade.

Algae growth; soil pH may be low

Increase drainage and establish thicker stand of turf. Aerate compacted areas, and increase sunlight in shaded areas.

Small green plants are growing on bare soil or in thin turf.

Moss; occurs in poorly drained or compacted areas, usually more severe in shade at low fertility and in low pH soil

Increase drainage and establish a thicker stand of turf. Aerate compacted areas, and increase sunlight in shaded areas. Apply fertilizer and lime according to soil tests.

Turf appears dry and bluish-green. Footprints remain after walking on turf, and grass wilts.

Drought

Irrigate turf.

Large areas grow poorly or wilt rapidly in sandy soil. Turf grows slowly and does not respond well to fertilizer and irrigation. Root system is poor.

Nematodes

Fertilize and irrigate more frequently to compensate for the compromised root system. This does not mean fertilize and water more, just more often. For example, if you normally apply 1 lb N/1,000 sq ft/month during the growing season for your lawn, you may want to apply ½ lb N/1,000 sq ft/ every two weeks instead. Do the same with watering; if you normally irrigate 1 inch per week, you may need to irrigate ½ inch every 3 days to 4 days during dry periods.

Submit samples to local Extension agent to determine if levels are high enough to cause damage and warrant treatment.

Many small twigs broken off

Squirrel damage

Squirrels prune twigs for nest building and often prune more than they need.

Wind, ice, or hail breakage

Prune to remove weak branches.

Twig pruner; twig girdler (insects)

Rake up and destroy fallen twigs.

Construction damage to trees; soil compaction

Protect trees during construction. Choose species adapted to heavy soils. Observe proper planting practices.

Large areas of split bark; no decay evident

Cold injury (typically at base of main stem, but can be elsewhere in sensitive plants like pittosporum)

Allow plants to go dormant in the fall by avoiding practices that promote late flushes (late fertilization and late heavy pruning).

Sunscald (damage on south or west side)

Cambium of thin-barked, young trees is damaged by temperature fluctuations on extremely cold days. Use tree wrap or block sun with boards on bright winter days.

Mechanical injury (lawn mower, weed trimmer)

Dig up or kill grass and replace with mulch to avoid mowing too close to tree base.

Lightning injury

Monitor condition of tree going forward.

Large areas of split bark; decay evident in wood

Secondary decay from wounds described above

No adequate controls. Remove loose bark. Water and fertilize tree at appropriate times.

Fungal or bacterial canker (any of several)

Submit sample to local Extension agent or NC State's Plant Disease and Insect Clinic (PDIC) for laboratory diagnosis. Prune out and destroy affected stems where possible.

Conks or mushrooms growing from branches or trunk

Fruiting structures of wood-decay fungi

Control is usually not possible. Consult a professional; branch or tree removal is recommended if damage is extensive and tree is a hazard to persons or property. Note that fungal structures are not present on all trees with decay.

Gelatinous, orange masses coming from needles, stems, trunks, or woody galls of juniper species in the spring

Gymnosporangium rust fungi

Spores formed here will infect different groups of woody rosaceous hosts, depending on the species. If feasible, galls and dead branches can be pruned out. Do not plant crabapples and junipers within 2 miles of each other.

Gray-white powdery growth on leaves; leaves may be distorted

Powdery mildew (fungal disease)

Improve air circulation. Rake up and destroy leaves in fall. Use labeled fungicides if aesthetics are severely impaired and plant is not too large.

Black, sooty growth on leaves and/or stems that comes off when rubbed with thumb

Sooty mold fungi that grow on honeydew secreted by insects

Identify insect pest (aphid, scale, psyllid, whiteflies, mealybugs). Optimize irrigation and fertilization. Dislodge insects with strong stream of water. Use horticultural oils or labeled insecticides as a last resort.

Brown, dead areas on leaf margins

Leaf scorch (caused by insufficient transport of water to leaves)

Water deeply during dry periods. Scorch is usually caused by hot, dry weather, but root rots or other root damage can also be involved.

Bacterial leaf scorch (particularly on sycamore, pin oak, and sometimes redbud)

This systemic and chronic infection by a xylem-inhabiting bacterium has no cure.

Dessication by winter winds

Water or shade plant in winter. Consider moving plant to a protected area.

Chemical injury

Injury can occur where herbicides are used too close to plants on windy or hot days or when roots grow into an herbicide-treated area.

Plant wilted; may have poor color; limited new growth

Dry soil

Water deeply during drought.

Root rot (fungal disease)

Improve drainage, and provide optimum growing conditions. Submit sample to local Extension agent or the PDIC to determine which root-rot organism is involved to better choose resistant or tolerant plants.

Nematodes

Submit soil sample to lNCDA&CS for an assay to determine if nematodes are present. If so, use resistant plants, and provide optimum growing conditions. No chemical control is effective.

Vascular wilt diseases

Submit sample to local Extension agent or the PDIC for laboratory diagnosis.

Waterlogged soil

Improve drainage.

Plant is root-bound

Cut root ball in several places before transplanting so roots will grow out into soil.

Girdling roots

Plant's own roots have grown around base of trunk and strangled plant. Plant properly, and do not plant or mulch too deeply.

Transplant shock

Do not transplant excessively large trees. Water often and deeply until established. Avoid excessive fertilization.

Bark beetles and other borers

Prune out and destroy dead or dying wood. Keep trees healthy and growing vigorously. Beetles and borers are often secondary problems. Protect nearby trees of the same species with a labeled insecticide.

Scattered twig and branch dieback

Borers (holes and tunnels in branches)

Provide optimum growing conditions. Submit sample to local Extension agent or the PDIC for diagnosis before attempting chemical control. If possible, prune out and destroy affected branches.

Cankers

Prune out affected branches, going several inches into clean wood. Destroy clippings.

Dark or sunken lesions on woody stems

Cankers

See above.

lnterveinal yellowing of leaves; no wilting

Nutrient or mineral deficiency

Complete a soil test. Improve drainage.

Waterlogged soil resulting in poor transport of nutrients to leaves

Improve drainage, and choose well-adapted species.

Large, rough, woody galls at base of tree and on roots

Crown gall (bacterial disease)

Depending on the species, the tree or shrub may continue to perform for years despite the disease.

Few or no flowers

Cold injury

Protect during cold (if practical).

Improper pruning

Some plants flower only on old wood. Prune spring-flowering plants after they finish flowering—not in the fall. Drastic pruning can reduce flowering.

Overfertilization with nitrogen

Nitrogen fertilization stimulates leaf production and reduces flower production.

Excess shade

Grow plants in proper amount of light.

Incorrect fertility

Complete a soil test.

Young plant

Some plants will not flower until they reach a certain age or until they become established following transplanting.

Galls on branches

Various fungal and bacterial diseases

Prune out and destroy galled branches. Submit a sample to local Extension agent for laboratory diagnosis.

Various insects

Most galls are harmless. Prune out galled branches.

Rapid dieback of new growth; blackening or browning of leaves; plant appears scorched

Fire blight (bacterial)

This blight occurs only on rosaceous hosts, such as pear, cotoneaster, and flowering quince. Prune out and destroy infected branches to a foot below discoloration. Reduce nitrogen fertilizer. Remove water sprouts. Use resistant species or cultivars.

Webs or tents on foliage and small branches; numerous worms

Eastern tent caterpillars (spring) or fall webworms (late summer to fall)

Disturb the web; prune out and destroy affected areas. Remove egg masses during winter. Use Bacillus thuringiensis (Bt) sprays or a labeled insecticide.

Proliferation of branches at specific points on the plant, forming a "witches' broom" effect

Insect injury

Prune out and destroy affected areas.

Fungal, viral, or mycoplasma disease or certain herbicides

Prune out and destroy affected areas. If seen in roses and other symptoms of rose rosette are present, pruning is not reliably effective, so remove and destroy the plant. See “Diseases and Disorders,” chapter 5.

Yellow or orange pustules on leaves, stems or fruit; infected leaves may drop; rusty colored spores on lower leaf surface

Rust (fungal diseases)

Replace with a resistant species or cultivar. Use a labeled fungicide in certain cases. Do not plant junipers and crabapples within 500 feet of one another.

Brown, gray, green or yellow crusty, leaf-like growths on trunk and branches

Lichens

Lichens are a combination of algae and fungi; they grow in moist, shady areas and do not harm the plant. Their presence in abundance on smaller plants indicates that the plant is unthrifty for other reasons.

White frothy material on foliage

Spittlebugs

Control is usually not necessary.

Early leaf drop or early fall color

Environmental stress such as drought, compacted soil or transplant shock

Improve soil conditions. Water if dry, and apply mulch. Do not fertilize with a high-nitrogen fertilizer.

Various insects or diseases

Submit sample to your local Extension agent or the PDIC for laboratory diagnosis.

Browning of tips of conifer needles; faint yellow bands about ⅛-inch wide across groups of needles

Ozone injury

No control needed. New growth should be okay.

General browning of conifer needles

Drought

Water deeply during drought, and apply mulch.

Salt injury

Do not use de-icing salt on sidewalks or roads near trees or shrubs.

Pine wood nematode

Submit a sample to NCDA&CS for an assay to determine presence of nematodes. Remove and destroy affected trees. This nematode is severe only on nonnative species, particularly Japanese black pine.

Waterlogged soil

Improve drainage.

Transplant shock

Do not transplant excessively large trees. Water often and deeply until established, and avoid excessive fertilization.

Girdling roots

Plant's own roots have grown around base of trunk and strangled plant. Plant properly, and do not plant or mulch too deeply.

Plant is root-bound

Cut root ball in several places before transplanting so roots will grow out into soil.

Animal urine injury

Heavy irrigation will promote recovery of spots by leaching salts from the soil to reduce concentration.

Fungal canker

Check trunk and branches for cankers. Prune out and destroy affected branches, going several inches into clean wood.

Sour-smelling sap oozing from cracks in tree bark

Slime flux (bacterial disease)

Provide optimum growing conditions. Avoid wounds to roots, which are entry points for the bacteria. Remove any loose bark.

Yellow and green mottle or mosaic pattern on leaves; leaves may be distorted

Viral disease; particularly common in nandinas, camellias, and roses

In most cases symptoms are not sufficiently severe to impair the aesthetics. Removal of plant may be necessary, especially in the case of rose rosette (see “Diseases and Disorders,” chapter 5).

Oozing sap on trunk

Environmental stress

Drought or waterlogging can cause trees to ooze excessively.

Mechanical injury

Prevent lawn mower and weed trimmer injury.

Disease or insect damage

See information on specific diseases.

Brown leaf spots

Fungal or bacterial disease (any of several)

See information on specific diseases, or submit sample to local Extension agent or the PDIC for laboratory diagnosis. Late in the season, diseases can be secondary as leaves senesce.

Herbicide injury

Avoid using herbicides on hot, windy days, and follow label directions.

Leaves chewed or completely eaten

Various caterpillars, sawflies, or leaf beetles

Tolerate some damage. Keep plants healthy with water and fertilizer. Identify the insect, and use Bacillus thuringiensis (Bt) or labeled insecticide while insects are small and before damage is extensive. If the insect is cankerworm, apply metal bands around tree.

Waxy, scalelike structures tightly attached to leaves, twigs, or branches

Various scale insects

Submit sample to local Extension agent or the PDIC for laboratory diagnosis. Use dormant oil or horticultural oil.

Young leaves puckered, curled or distorted; clear, sticky substance on leaves; clusters of small insects on undersides of leaves

Aphids

Encourage natural predators. Dislodge with strong stream of water. Use horticultural oil or a labeled insecticide.

Serpentine trails or blotches in leaves

Leafminers

Management is not usually necessary.

Leaves stippled (pinpoint yellow spots); leaves off-color (gray, silver, white, or yellowish); varnish-colored specks on underside of leaf; may appear to be dirty due to fine webbing and dust that collects

Lacebugs, spidermites

Spray undersides of leaves; a strong stream of water will dislodge some of the pests. Use horticultural oil or a labeled insecticide.

Bags constructed from plant material hanging from branches

Bagworms

Prune out affected branches. Handpick and destroy bags. Spray with a labeled insecticide in late spring when bags are barely visible.

Galls (abnormal growths on leaves, stems, or other tissues)

Various insects or mites

There are no chemical management options for gall insects, but the plants will not be seriously harmed. Prune off and destroy galls.

Water sprouts; suckers

Environmental stress; excessive pruning (ondogwoods in mountains may indicate dogwood anthracnose)

Pull or cut off water sprouts and suckers.