Diagnosing Plant Problems

Bacterium

A single celled, microscopic organism having a cell wall but no chlorophyl. Reproduces by cell division.

If there is uniform damage over a large area of land, what type of damage should be suspected?

Abiotic

How does damage from herbicides happen?

Accidental direct application to a non-target plant. Drift of the herbicide from a nearby site. Volatilization of the product, which then moves as vapor from the application site. Uptake through the roots if the herbicide was applied to the soil.

What are examples of insects that may cause galls?

Aphids, wasps, midges, mossyrose call wasp, and poplar petiole gall midges.

What is leaf and stem distortion accompanied by off-color foliage a result of? What is this type of damage often confused with?

Aphids. Confused with injury from growth regulating chemicals.

What are phytoplasms? What are they vectored by? What do they cause? What are the above ground symptoms?

Bacterial parasites that infest plant phloem tissue, vectored by leaf hoppers, cause root distortion and reduced ability to transport nutrients, above ground symptoms can include chlorosis, dwarfism, and witches broom.

What are common causes of pollination problems?

Cold, wet, or windy weather can discourage pollinators and rainfall during bloom can prevent wind pollinated plants from being pollinated.

What should you consider when looking for mechanical damage?

Consider if there has been recent excavation, construction, or paving on the site. Examine for the type of damage to determine the cause of damage.

What can mis-timed or overenthusiastic pruning cause?

Could allow disease organisms into a tree in wet weather, may cause susceptibility to a cold winter, and possibly death, among others.

What is often the best response to fungal diseases in fall/winter?

Cutting back the diseased parts and properly disposing of them.

What is the primary sources of diagnostic information for damage caused by environmental factors?

Damage patterns and weather records.

What type of damage do sucking insects cause?

Damage plants by directly feeding and sometimes inject substances that cause symptoms ranging from simple stippling of leaves to extensive disruption of the entire plant.

What type of damage do eriophyid mites cause? What are these symptoms often confused with?

Distorted new growth, rolled leaf margins, and swollen veins. Often confused with damage from growth regulators.

What is the difference between drought and a short-term lack of water?

Drought is a long-term condition of dryness, short term lack of water is cultural problem with irrigation.

What causes twigs to look like they have been split by a sharp instrument? What insect often split the branch enough to kill its tip?

Egg laying by sucking insects such as treehoppers and cicadas. Cicadas.

If there is general decline of a plant or specific branch, what should you examine it for? What cases the signs you are looking for and what are examples of potential culprits?

Examine it for holes in the bark, frass, or pitch. These are signs of borers that feed under the bark in cambium tissue, solid wood, or xylem tissue. Examples are mountain pine beetles, European elm bark beetles, raspberry crown borers, and sequoia pitch moths.

What are some weather extremes that may cause problems for plants?

Extreme cold Extreme heat Early or late freeze Physical damage

What do sowbugs and pillbugs feed on and are they considered damaging to living plants?

Feed on decaying vegetation. Only damaging if populations are high.

What damage do slugs and snails cause?

Feed on low growing foliage and fruit - cause skeletonization or destruction of soft tissue - look for slime trails.

Where do symptoms of deficiencies in phloem-mobile nutrients develop?

Fist in older leaves

What results from wide day-night temperature fluctuations in winter?

Frost cracks - longitudinal separations of bark and wood that generally occur on the southwest side of a trunk

What is the most common frost damage in the early spring?

Frost damage on leaves that emerged early and got a late frost.

What infections are common on young, tender leaves in a cool, damp early spring?

Fungal and bacterial

In fall and winter, when days grow cooler and damper, what type of infection is common?

Fungal infections

What plants are most likely to experience cold damage and where on the plant is damage most likely to occur?

On the least hardy plants in their least hardy tissues.

When looking for patterns of distribution in the landscape, what questions should you ask?

One species or several? One location or scattered? Similar locations?

What is a common mistake done by a well intentioned gardener when a plant is wilting?

Overwatering without determining the cause of the problem.

What chemical is commonly used for broad leaf weed control in landscapes and agricultural situations?

Phenoxy (2, 4-D)

What is the best solution for low areas with poor drainage?

Plant adapted plants in that area

What are some possible cultural practices that may effect the health of a plant?

Planting error Mulching error Watering error Pruning injury Herbicide injury Fertilizer application Construction damage

Describe symptoms of root contact chemical damage

Poor root development. Injured roots and possibly dead root tips. Aboveground parts may show nutrient and water stress symptoms. In severe cases wilting can occur even when soil is wet.

What is the result of chlorophyll being destroyed locally at the feeding site but toxins do not diffuse throughout the leaf. What are common causes of this injury?

Spotting or stippling. Aphids, leafhoppers, and plant bugs.

What results from failure to correct root system issues in trees?

Structural issues later in life and girdling roots that can cause the tree to break off and fall over.

If petioles are weakened and leaves fall in early summer, what should you suspect? What do you do to test your suspicion and why?

Suspect petiole and leaf stalk borers. These burrow into petioles near leaf blades or bases. Cut open a petiole to look for a small moth or sawfly larva.

What is the best diagnostic tool for identifying pathogen damage?

The characteristic appearance of the damage since the pathogen is too small to see with the naked eye

What are the most important clues for identifying an insect pest?

The location and type of feeding damage

Why are bacterial and viral infections often hard to diagnose correctly?

The pathogen is too small to see and often the symptoms may not be specific enough and laboratory analysis may be needed.

What does viral infection variability depend on?

The virus and the plant

How are weather extremes different from climatic stresses?

They are usually unexpected, and temporary.

What is good information to find when looking up a plant for identification?

USDA hardiness zone, preferred sun exposure, water needs, and common diseases are pests it is susceptible to.

What is an indication that a nonliving factor is probably the cause of damage?

Uniform damage patterns

What damage does spring frost cause?

Uniformly kills new, succulent growth. New growth emerging after the frost will be healthy.

What might be the culprit if a twigs bark is girdled (cut, removed, or clamped all the way around)?

Vine weevils or twig-girdling beetles

When describing the problem with the plant what questions should you answer?

What parts of the plant? How extensive? Color changes? Insects present?

What causes the development of severe toxemia?

When toxic saliva causes the leaves to curl and pucker around an insect - severe aphid infestations may be the cause.

What are the similar above ground symptoms of drought and waterlogging (saturated with water)?

Wilting, chlorosis, and abscission of older leaves. Eventually if stress persists, wilting and necrosis occurs on tips and inter veinal regions of recently expanded leaves and new growth.

Does planting treed and shrubs too deep cause problems?

Yes

Can plants recover from nitrogen deficiency?

Yes - when more nitrogen is applied, most plants can recover quickly.

What is the cause of blossom end rot and what is the cure?

a calcium deficiency, adding water is the solution.

Which can survive at lower temperatures, the above ground plant parts or the root system?

above ground parts

What are other symptoms (besides leaf symptoms) that can be caused by bacterial infection?

cankers and gumming

What is the result of a rapid change from low to high light?

destruction of chlorophyl - yellowing and necrosis

What is the result of frozen dividing cells on outer portions of leaves while still inside the bud?

distorted or lace like leaf blades

What time of year does damage to lower parts of the plant occur?

fall/early winter

What is the most common site of injury from a herbicide?

foliage

Where do problems occur from translocated chemicals that travel through the xylem?

in older foliage

Where do problems occur from translocated chemicals that travel through the phloem?

in the plants new growth and meristematic regions.

Abiotic

is this an image of a biotic or abiotic problem?

When should a plant that forms blooms on new wood be pruned?

late winter or early spring

When should a plant that forms blooms on old wood not be pruned?

late winter or early spring

What time of year does cold damage to buds occur?

late winter/early spring

Are millipedes damaging to plants?

no

Does a sudden injury that does not spread require treatment?

not usually

Why does staking a tree often lead to damage?

often the stakes are improperly put on and/or never removed which causes the wires and sometimes the stakes to constrict the trees growth.

What are common chronic environmental problems?

poor drainage drought nutrient deficiency pollination problems

What part of the fungus infecting a plant is usually visible?

the fruiting bodies

What is characteristic of bacterial spots on leaves?

they are usually papery and dead in the center and have a water soaked appearance with a lighter yellowish halo where the tissue has not dies yet.

What is the best response to climate drought?

to plant species that are adapted to it

What type of plant suffers the most from bad planting practices and why?

trees because they grow so slowly over such a long period of time that the problem may not become apparent until years later

What are the symptoms of nitrogen deficiency?

uniform chlorosis of older leaves, finally leading to necrosis and loss of the leaves.

When does cold damage to the roots become evident in the above ground parts of the plant?

when shoots begin to grow in the spring - leaf expansion may be incomplete because of restricted water and nutrient uptake - Leads to smaller than normal leaves. May lead to eventual wilting and/or death.

What makes even rows of holes in tree trunks and may cause missing flower petals?

yellow-bellied sapsucker

Can herbicides harm plants other than weeds?

yes

Can viruses be transmitted by insects?

yes - some viruses have a specific insect vector

How do you begin to determine if damage to a plant was caused by cold?

Know the temperature drop and the USDA cold hardiness zones.

What is common in lat spring early summer when new leaves are suddenly exposed to full sun? Is this damage deadly?

Leaf scorch - new growth will spread beyond the damaged leaves and plant is usually fine

What damage do spider mites cause?

Leaf stippling, damaged leaves turn pale on underside - severe infestations cause leaf bronzing and death. Foliage may appear dirty due to the presence of small, fine webbing mixed with eggs and frass on the underside of leaves.

What are random stipple patterns on leaves caused by?

Leafhoppers and mites

Leaves are tied with silken threads or rolled into tubes. What may have done this?

Leafrollers or leaftiers

What are the two major categories of factors that cause plant damage and what factors are included in each category?

Living organisms such as pathogens (fungi, bacte- ria, viruses, and nematodes) and pests (insects, mites, mollusks, mammals, and birds) Nonliving factors such as mechanical damage (e.g., breakage or abrasions), environmental condi- tions (e.g., extremes of temperature, light, mois- ture, or oxygen), and chemicals (e.g., herbicides or nutritional disorders).

What does root damage look like in container grown plants and where does it occur?

Looks black or spongy and lacks new growth or new root hairs. Found on the periphery of the root ball near the container edge.

What is a common problem with sheering of evergreens?

Many wont break new growth from old wood, so sheering often leaves permanently dead stems.

What family of plants is especially sensitive to Glyphosate (Roundup)?

Members of the rose family such as blackberries and rhaspberries.

What is the most common cause of chewed bark and cambium tissue on small trees and shrubs.

Mice, rabbits, squirrels, or bevers - look for teeth marks.

What are the damage patterns of heat damage?

Most likely to occur in the early afternoon, on the outer, unshaded leaves of the plant facing the southwest, and on the parts of the plant farthest from water carrying roots, stems, and leaf veins.

IF mulch is added year after year automatically, what problem may arise?

Mulch levels could reach harmful depths

What are mobile nutrients?

N, P, K, Mg, and Ni

What is the most common nutrient deficiency?

Nitrogen

Do all viruses have the same symptoms?

No - each virus has its own set of symptoms.

Are organic herbicides less damaging than conventional herbicides?

No - they can be just as damaging

Does the distorted foliage caused by phenoxy recover?

No- it must be removed from the plant is aesthetics are a problem.

Describe the symptoms and patterns of shoot/foliage contact chemical damage

Occur over the general plant canopy and does not spread with time. Chlorotic or necrotic spotting that is usually uniformly and evenly distributed. Color is usually uniform across the spot with a sharp edge. You may be able to see the application pattern.

What may general uniform stippling, flecking, or chlorotic patterns on spruce needles be caused by? What may this be caused by on other plants? What type of feeding pattern causes this?

On spruce needles - adelgid damage. On other plants - lace bugs. Sucking.

What are some questions that can be asked when assessing leaf damage?

IS the entire leaf affected or just between the veins? Is the damage in the center of the leaves or the edges? Is it circular or irregular?

Where do symptoms of deficiencies in phloem-immobile (can only move in the xylem) nutrients develop?

In new growth.

How might chronic environmental problems manifest?

In poor plant growth over time

Where are symptoms shown for an immobile nutrient deficiency and why?

In the new leaves because the nutrients can not be moved from the old leaves to the new leaves that are deficient.

Where will symptoms be shown first when there is a mobile nutrient deficiency and why?

In the older leaves because the plant will move those nutrients from the older leaves to the newer leaves

What are toxicogenic insects and what type of damage do they cause?

Insects that secrete phytotoxic substances that result in damage called phytotoxemia or toxemia.

What are some ways that humans can unintentionally harm a trees root system?

Irrigation, driving, construction, landscaping.

When determining what is normal, what questions should you ask?

Is it normal for the plant? Is it normal for the season? Is it harmless or beneficial?

biotic

Is this a biotic or abiotic problem?

random

Is this uniform or random?

uniform

Is this uniform or random?

What problem may occur when a fine mulch is applied?

It could form a water resistant layer.

What is a whole plant shows signs of a nutrient deficiency?

It is likely a deficiency in a partly mobile nutrient such as S or Mo

What might happen to phenoxy when applied during warm, windy conditions?

It may spread from the site of application to non-target plants.

What are rust diseases?

Rust diseases are a specialized type of fungi that require two host plants, which they alternate between during their life cycle.

Distinct portions of the leaf are missing: 1. Distinct notches cut from leaf margins. 2. Circular holes cut from margins. 3. Small, randomly scattered holes. What insect may have caused the damage in each case and what method of feeding is this caused by?

1. Black vine weevil adults 2. Leaf cutter bees 3. Beetles, chafers, weevils, and grasshoppers. chewing/rasping

What are the 10 step method of plant problem diagnosis?

1. Identify the plant 2. Describe the problem 3. Determine what is normal 4. Observe where the damage occurs on a plant 5. Look for patterns of distribution in the landscape 6. Time of year 7. Examine spread over time and space 8. Review cultural practices 9. Identify environmental conditions 10. Determine likely cause of damage

What does the damage from Phenoxy (2, 4-D) look like?

A curling, fan shaped pattern of distortion, most damaging to new growth.

What tears or cuts branches?

Cattle, goats, deer, and horses.

What is a common problem with trees grown in pots and what should be done about this problem?

Circling roots - they should be untangles and possibly cut off

What is the easiest way to diagnose a nutrient deficiency?

Be familiar with the common nutrient deficiencies in your area.

Why is cold damage to roots more of a concern with container grown plants?

Because ground soil temperatures generally stay fairly stable but container soil temperatures fluctuate much more.

Why are nutrient deficiencies in plants difficult to diagnose?

Because symptoms are similar to many other types of stresses.

Why are dead patches of bacterial infections usually between the veins?

Because the veins stop the spread of the bacteria.

If there is non-uniform/scattered damage over a large area of land, what type of damage may be suspected?

Biotic

What are immobile nutrients?

Ca, Fe, Mn, Zn, Cu, and B

What is the cause of corky spots in apples and bitter pit in pear and what is the cure?

Calcium deficiency - using calcium chloride foliar spray and proper water and nitrogen management.

The entire leaf blade is consumed and only the tough midvein remains - what insect may have caused this damage and what method of feeding is this caused by?

Caterpillars, canker worms, or webworms - chewing/rasping

What might damage from root, stem, or branch feeders such as scales and mealybugs look like?

General decline of the entire plant or plant part - poor color, reduced growth, or dieback.

What chemical is commonly used for weed control and often causes unintended damage to other plants?

Glyphosate (Roundup)

What do you do if there is a discolored or swollen area on a leaf? What may have caused this damage?

Hold it up to the light to look for insects or frass in the damaged area. The culprit may be leaf miners, which feed between the upper and lower leaf surfaces.

How do fungal infections often present?

Present as roundish spots of varying sizes, sometimes with a bullseye appearance, not stopped by the veins, and sometimes have fruiting bodies within the spots

Random

Random or uniform?

random

Random or uniform?

What is the result of toxic effects spreading throughout the plant? What is this condition called? What may cause this?

Reduced growth and chlorosis. Called systemic toxemia. Psyllid yellows of potatoes and tomatoes, scale insects, and mealybug infestations.

What is the result of rapid change from high to low light?

Reduced growth and leaf drop - new leaves are larger, thinner, and darker. Flowering is reduced, delayed, or absent.

What PNW plants does iron deficiency commonly effect? What needs to be addressed when this happens?

Rhododendron, Calluna, Erica, Blueberry, and Cranberry. The pH needs to be addressed.

What might general decline of a plant along with chewed roots indicate?

Root-feeding larval stages of weevils, beetles, and moths.

What is a common nematode found in gardens?

Root-knot nematode which causes distorted, knobby roots in carrots, brassicas, and other plants.

Frass

Sawdust-like material associated with insects chewing into plant tissue.

What is the best way to protect a trees root system during construction?

Securely fence off the entire root area, well beyond the edge of the canopy.

What kind of pest does damaged leaf surfaces (especially skeletonized) indicate? What method of feeding is this caused by?

Slugs, beetle larvae, pearl-slugs (pear sawfly larvae), elm leaf beetles, or thrips. Chewing/rasping