Eight Steps to Diagnosing a Problem
Diagnosing a plant problem, whether flowers, vegetables, indoor plants, or anything else you’re growing, is often a challenge since there can be so many different causes. It's like being a detective. Instead of uncovering a murder, you're trying to figure out who or what is bugging your plants.
During the diagnostic process you need to ask lots of questions, collect, and evaluate information to figure out a likely cause. A good detective uses their powers of observation and reasoning, and if you want to identify plant problems you'll need to hone these skills.
Here are the main steps:
Step 1: Observe
Try to visit your garden daily and get to know what your plants look like when they're healthy — so you'll notice any problems right away. When you do see something out of the ordinary, stop for a closer look. What caught your eye? Off-color foliage? Holes in the leaves? The key to success is taking time to look closely. It's the single most important action you can take.
Step 2: Identify the Plant
What kind of plant is it? Some types of plants are particularly susceptible to certain pests or disease problems. Knowing the plant and its proper name are important when searching for pest information. Good reference materials can help you match your observations with descriptions or photographs of typical plant pests and diseases, and their related signs and symptoms. For comparison purposes, have a clear idea of the size, color, form, flowers, or fruit of a healthy version of the plant.
Step 3: Define the Problem
*Specifically identify what appears to be wrong:
- Are there visible signs of the cause of the problem?
- What are the symptoms?
- When was the problem noticed?
- Was the damage sudden or gradual?
- What percentage of the plant is affected?
- How severe is the injury?
Step 4: Assessing the Problem
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Are the Leaves Being Eaten?
- How long has the plant been in its current location?
- Has anything changed for the plant itself or near it?
- What’s the weather been like – frosty cold, devilishly hot, super windy and dry?
- Did you fertilize recently, or use some chemical pesticide?
The culprit might be an insect, slug or animal pest. Large holes in the middle of the leaf can indicate beetles, caterpillars and slugs. Shredded foliage or plants eaten right down to the ground might be the work of an animal, such as a deer or squirrel.
Are the Leaves Discolored?If so, how? Silvery, bronzed or stippled foliage may indicate the presence of plant juice-sucking insects such as aphids and spider mites. Pale or mottled leaves can indicate an environmental or nutrition problem.
Are there Spots on the Leaves?They may be caused by a disease. But they can also be the result of insect feeding or environmental factors. Some plants are notorious for their susceptibility to certain diseases.
*Consider the history of the plant and its surroundings
*Narrow down your list of possible suspects by ruling out those problems you know for certain are not the cause of the problem.
Step 5: Look for the Culprit
Do you see insects, eggs or droppings? Some insects are difficult to see but they leave telltale signs. For example, some cabbageworms are so well camouflaged you may not see them, but you'll see their black droppings. Eggs may be clustered on the undersides of leaves or on new growth, so be sure to look there, too. Keep in mind that the insects you see may not be causing the symptoms. Ants, for example, are sometimes found on damaged plants and are assumed to be the culprit. But they generally don't harm plants — they're after the honeydew (a sugary secretion) left by the real pests, usually aphids. Other insects, such as lacewing or ladybug larvae are beneficial insects that may already be busy solving the problem by hunting down the pests.
Step 6: Look for Other Signs and Symptoms
Examine plants for anything out of place. Some pests are so tiny you're unlikely to see them, but on close inspection you'll see signs of their presence. For example, spider mites are smaller than a pinhead but reveal their presence with the silky webbing they produce. Though slugs feed at night and usually hide out during the day, the shiny slime trails they leave behind are telltale "footprints."
Step 7: Make a Preliminary Diagnosis
With the information you collected, decide what you think the cause of the problem is.
- Examine the entire plant and the area around it, including the soil.
- Check out the leaves (both top and undersides), stems, roots, fruit, and flowers.
- Look for signs and symptoms of pests:
*A few things that can help with your detective work:
Step 8: Is it Necessary to Take Action?
Consider the options. Don't immediately switch into "spray mode" if you recognize a pest or its damage. If you see holes in the foliage but no insects, it could be that they've already come and gone. If there are only a few pests, you may want to just track the situation for a day or two and see what happens. Giving the plant a fortifying drink of water, spiked with some liquid organic fertilizer may be all that's required. If it's the end of the growing season, control may not be warranted. If, on the other hand, it's early in the season and the plant is at risk, you may need to act quickly. Diseases pose different challenges. Most products that control diseases are preventative — they won't cure a disease but can keep it from spreading. You may also be able to keep a disease problem in check by removing and destroying affected leaves or parts of the plant.
Remember that many pests and diseases can be kept in check with good gardening practices. Pesticides and fungicides — even organic ones — should always be a last resort.
Pest and Disease Guides
The below resources provide information on identifying and controlling your most common insect pests and critters—from aphids and hornworms
to rabbits and deer. They also address plant disease from blights to wilts.
The first step is to identify the problem! The second step is to control it! Begin your quest below:
Resources - Problem Solver:
The Old Farmer's Almanac Pest and Disease Guide
Utah State Extension Service - Fruit, Vegetable and Herb