Tree Diagnosis and Treatment Practice Questions

Correct answer: D. Fungal fruiting structures on the lower trunk

A sign is physical evidence of the damaging organism itself, such as the insect, its frass, or a fungus's fruiting structures. A symptom is the plant's response to injury. Wilting, discolored foliage, and dieback are all symptoms, and each can have many different causes, so none of them points to a specific agent the way a sign can.

• A: Wilting is a symptom, the plant's response to injury, and it has many possible causes.
• B: Yellowing and browning are discoloration symptoms, not evidence of the organism itself.
• C: Dieback is a symptom; it shows the tree's response but not what caused it.

Source: Overview of Plant Diagnostics, Penn State Extension

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Correct answer: A. A nonliving (abiotic) cause such as drought or a chemical exposure

When damage appears at the same time on several unrelated species, a nonliving cause such as weather, drought, or chemical exposure is the most likely explanation. Most pathogens and many insects attack only certain hosts, so a biotic problem usually shows up on one species and spreads over time. The host-specific disease and the single-genus insect both contradict the multi-species pattern.

• B: A host-specific disease would be limited to one kind of plant, not four unrelated ones.
• C: An insect restricted to one genus could not damage dogwood, maple, holly, and perennials at once.
• D: Infectious diseases build up and spread over time; sudden, simultaneous damage on unrelated plants points to an abiotic cause.

Sources: Overview of Plant Diagnostics, Penn State Extension ; Biotic vs. Abiotic - Distinguishing Disease Problems, Iowa State University Extension and Outreach, Yard and Garden

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Correct answer: B. Identify the species of the tree

Identifying the tree comes first because most insects and pathogens attack only certain hosts, so knowing the species quickly narrows the list of likely problems. It also tells the arborist what is normal for that tree and what site conditions it needs. Looking for signs, testing soil, and sending samples are useful later steps, and they are far more efficient once the host is known.

• A: Lab samples can help later, but both the lab and the arborist need to know the host first.
• C: Looking for signs is an important step, but it is guided by knowing which pests attack that species.
• D: A soil test may help later; it is not the first step and does not identify the host.

Sources: Diagnosing Disorders of Trees (Appendix A: The Ten S's of Tree Disorder Diagnostics), North Carolina Forest Service ; Overview of Plant Diagnostics, Penn State Extension

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Correct answer: C. A favorable environment

Disease develops only when a susceptible host, a pathogen, and a favorable environment come together. Here the host is susceptible and the fungus is present, so the dry spring removed the environment corner: most fungal spores need free water on the plant surface before they can germinate and infect. Vectors matter for some diseases, but they are not one of the triangle's three corners.

• A: The stem says the species is susceptible, so the host corner is present.
• B: The fungus is well established at the site, so the pathogen corner is present.
• D: Vectors appear in some expanded models, but the dry spring points to the missing environment corner.

Source: Extension Gardener Handbook, Chapter 5: Diseases and Disorders, NC State Extension

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Correct answer: C. Combining tactics to prevent damage and using pesticides only when monitoring shows a need

IPM focuses on long-term prevention of pest damage by combining biological, cultural, mechanical, and chemical tactics. Pesticides are not ruled out, but they are used only when monitoring shows they are needed and are chosen to affect the target pest as narrowly as possible. Calendar spraying and trying to eliminate every pest are the opposite of this approach, and IPM does not require refusing pesticides in every case.

• A: Calendar spraying ignores monitoring and thresholds, which are central to IPM.
• B: IPM can include pesticides when monitoring shows they are needed; it does not ban them.
• D: IPM aims to keep pests below damaging levels, not to eliminate every organism.

Source: What Is Integrated Pest Management (IPM)?, University of California Statewide IPM Program (UC IPM)

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Correct answer: A. The pest level or condition at which control action must be taken

An action threshold is the point at which pest numbers or environmental conditions show that control is needed. Finding a single pest does not automatically justify treatment; monitoring shows when the threshold has been reached. Label rate limits, monitoring start dates, and tree removal decisions are separate matters.

• B: Label rate limits are legal application limits, not thresholds for deciding whether to act.
• C: A monitoring schedule is separate from the threshold that triggers control.
• D: Thresholds trigger pest control action, not tree removal decisions.

Source: Integrated Pest Management (IPM) Principles, U.S. Environmental Protection Agency

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Correct answer: B. On key plants and key problems, those most likely to need attention

A PHC program starts by listing the plants on a site and learning their likely problems, which reveals the key plants that are problem-prone and the key problems most likely to harm them. Concentrating monitoring there makes the best use of time and catches serious problems early. Spreading effort evenly wastes time on trouble-free plants, and waiting for symptoms or client requests gives up early detection.

• A: Equal effort on every plant wastes time on low-risk plants and dilutes attention to likely problems.
• C: Watching only plants with obvious symptoms gives up early detection, a core PHC principle.
• D: Client concerns matter, but monitoring should be guided by which plants and problems are most likely.

Source: Chapter 21: Plant Health Care and Integrated Pest Management (The Pacific Northwest Gardener's Handbook), Washington State University Extension

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Correct answer: A. Using a pesticide in a way that conflicts with its labeling violates federal law

Pesticide labels are legally enforceable documents. Every label states that federal law is violated whenever the product is used in a way that is not consistent with its labeling, and this applies to every registered pesticide, not only restricted-use products. Applying more than the label rate is illegal and does not control pests any faster.

• B: Applying more than the label rate is illegal and can injure plants and the environment.
• C: All pesticide labels are legally enforceable, not only restricted-use labels.
• D: Label directions are legal requirements, not suggestions.

Sources: Introduction to Pesticide Labels, U.S. Environmental Protection Agency ; Pest Notes: Understanding Pesticides (UC ANR Publication 74126), University of California Statewide IPM Program (UC IPM) ; Pest Notes: Understanding Pesticides (UC ANR Publication 74126), University of California Statewide IPM Program (UC IPM)

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Correct answer: B. Keep the pesticide in its original, labeled container instead

Pesticides should always stay in their original containers, because each label lists the directions for use, the ingredients, and the first-aid steps to take if someone is poisoned. A drink bottle can be mistaken for something to drink, even if it is marked or locked away. Diluting a pesticide does not make it safe to keep in an unlabeled container.

• A: A hand-written label lacks the directions and first-aid information, and the bottle can still be mistaken for a drink.
• C: Locking up pesticides is good practice, but moving them into a drink bottle is still unsafe.
• D: Diluting does not make it safe to keep in another container, and UC IPM advises against storing leftover pesticide solutions at all.

Sources: Storing Pesticides Safely, U.S. Environmental Protection Agency ; Pest Notes: Understanding Pesticides (UC ANR Publication 74126), University of California Statewide IPM Program (UC IPM)

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Correct answer: D. The spray killed predators that had been keeping the mites in check

This is a secondary pest outbreak. Broad-spectrum insecticides kill beneficial predators along with the target pest, and without those predators a previously minor pest such as spider mites can multiply past tolerable levels. Follow-up monitoring after any treatment should watch for this kind of flare-up, and selective products help prevent it. Resistance develops through repeated use, not from one spray aimed at a different pest.

• A: Resistance builds through repeated use, and the mites were not even the target of this spray.
• B: Mite outbreaks after broad-spectrum sprays are explained by the loss of their natural enemies.
• C: Stippling is the typical feeding damage of the spider mites that are present.

Source: Chapter 21: Plant Health Care and Integrated Pest Management (The Pacific Northwest Gardener's Handbook), Washington State University Extension

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