Pest and Disease Control
In This Section
In this section, you’ll find discussions, explanations, and directions for keeping your flower garden healthy, scouting tips for identifying common flower pests and diseases, and demonstrations for treating and controlling pests and diseases of flowers, flowering plants, and garden bulbs, including:
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- An introduction to pest and disease control for flowers and bulbs.
- A discussion of flower- and flower garden-specific pest and diseases.
- A discussion of bulb-specific pests and diseases.
- A checklist of proven good-gardening practices that keep flower gardens healthy.
- A discussion and step-by-step demonstration of how to treat fungal diseases in bulbs.
- A discussion and step-by-step demonstration of how to treat pest infestations in flower-bulb plantings.
- An introduction to Integrated Pest Management (IPM), used by professionals to prevent and rid flower gardens and bulb plantings of pests or diseases.
On This Page
Here, you’ll find discussions of the following pest- and disease-prevention and control subjects beneath each of the following titles:
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- Preventing Pests and Diseases in Flowers
- Start with Healthy Flowering Plants
- Preventing Pests and Diseases in Bulbs
- Good Bulb Garden Practices
- Integrated Pest Management (IPM)
- Quick References to Pest and Disease Control
Preventing Pests and Diseases in Flowers
Learn to recognize common symptoms of many flower pests, diseases, and nutrition problems so your landscape garden’s flowers and bulbs will grow healthy and beautiful.
Plants in poor health are susceptible to pests and diseases just as someone with a weakened immune system might develop pneumonia after a common cold. Flowers that receive too little water, are undernourished, or stressed by pests, heat, or cold often succumb to afflictions that wouldn’t phase stronger plants.
First, we’ll discuss problems with flowering plants, including annuals, perennials, and biennials. Next, you’ll learn about bulb pests and diseases.
Start with Healthy Flowering Plants
The best way to defend against insects and ailments, even before you plant, is to choose disease-resistant varieties, adaptable species, and many different kinds of plants that will encourage beneficial insects to stay in your garden.
When shopping for seed, transplants, or bulbs, check them for signs of diseases and pests [see: Selecting Healthy Plants and Choosing Healthy Bulbs].
Make your planting site welcoming to the plants you’ve chosen.
Rotate annuals through your beds from season to season. Because garden soil tends to harbor pests and spores of diseases that destroy repeat plantings, rotating plantings each season and year prevent them from multiplying.
Cultivating the soil prior to planting also helps eliminate lingering insects and disease-causing organisms. Cultivating exposes organisms to the sun, killing them or limiting their growth. Cultivate before planting and whenever you fertilize or remove weeds.
Pay attention to soil drainage, compaction, and organic content. As you’re digging, add compost or other organic matter. Working it into the soil is another way to help eliminate insect hiding places. It also destroys fungus spores that cause diseases such as damping-off disease, rust, or downy mildew.
Poor air circulation is another cause of powdery mildew, downy mildew, and other fungal diseases. Avoid overcrowding your plants, the most likely cause of poor air circulation.
Use porous floating row covers instead of sheet plastic to protect your germinating seeds or young plants. It protects new seedlings from insects, animal pests, and temperature changes, but still allows moisture to evaporate and escape instead of condensing on foliage.
Keep your plants evenly moist and properly fertilized. Spider mites and thrips, as two examples, thrive on dry, stressed plants.
On the other hand, always allow the soil surface to dry between irrigations. This simple practice helps prevent soilborne fungi spores from ripening and infecting your flowering plants.
If you detect insect pests, spray your plants with a stream of water early in the day after temperatures warm. You’ll dislodge them from their food source, and many will die because they are unable to climb back to your flower’s leaves.
Alwasy remove decayed or diseased plant matter promptly. Fallen leaves and decaying plant materials harbor pests and diseases that infest or infect surrounding plants.
Even debris that has fallen from healthy plants should be cleaned out, since slugs, snails, and other pests find it a convenient shelter.
Remove all weeds, which weaken plants through competition and provide another haven for pests and diseases.
Take positive steps by releasing beneficial and pest-predators. Addding green lacewings, ladybugs, and parasitic, stingless wasps to your flower garden will naturally and organically deal with many commons flower pests.
Preventing Pests and Diseases in Bulbs
The aim of all control measures for bulb pests and diseases are using good gardening practices designed to prevent and control infestations or infections.
Bulbs are surprisingly resistant to pests and disease, far more than many other flowering plants. Still, you should remain vigilant. Frequent inspections and scouting through your landscape is a must.
Good Bulb Garden Practices
Good gardening practices reduce the chance of pests and diseases taking hold in your bulb plantings or in surrounding flowers, shrubs, or trees.
Prevent Weeds.
Native weeds host insect pests and fungal spores. Mulching your beds, covering them with a layer of compost, or planting low-growing ground covers helps prevent their seeds from germinating and makes pulling weeds easy [see: Mulching Landscape Bulb Plantings].
Uproot and compost any weeds that do sprout while they are young and easy to pull.
The heat of vegetative decomposition in compost piles kills most pests and weed seeds. After composting, garden waste becomes rich organic compost suitable for your garden beds.
Organic compost contains beneficial living organisms, and it provides major and trace nutrients to feed your plants. It also is a great soil conditioner for improving soils that are too clayey or sandy.
Keep Gardens Clean.
Rid your yard of fallen leaves, plant debris, pruning litter, and dead foliage. All these are favorite hiding spots of slugs and snails, two of the most significant bulb pests.
Leaves and garden debris shelter eggs, larvae, grubs, and adult insect pests, as well as nematodes and many plant bacteria, viruses, and fungal spores.
Plant Only Disease- and Pest-Resistant Bulb Species.
Daffodil and other narcissuses, for example, have natural defenses against fungus, insect, and animal attack.
Plant Only Healthy Bulbs.
Good growers vigorously check bulbs while they are still in their growing grounds. Most bulbs sold by garden stores and nurseries, therefore, are in good health.
Check them carefully, and choose only bulbs free from pests and disease.
Avoid bulbs with cuts and nicks. Once planted, protect your bulbs during planting, cultivating, and lifting. Keeping bulbs healthy helps stop fungal disease spores from entering the bulb.
Control Pests Before They Damage Bulbs.
Sometimes, even in well-maintained gardens, pests gain a foothold.
Ants, aphids, Japanese beetles, various borers, mites, mollusks (slugs and snails), harmful nematodes, thrips, whiteflies, and wireworms all feed on bulbous plants.
Learn Bulb Disease and Pest Symptoms and Controls.
Avoid bulb species are susceptible to botrytis, mildew, and viral diseases. Knowing what to look for is an important skill for preventing diseases in your bulb plantings.
Practice Integrated Pest Management (IPM) Like the Pros.
Most horticulturists practice Integrated Pest Management, or IPM to stop and prevent future infections and infestations by pests and diseases.
Integrated Pest Management (IPM)
The goal of Integrated Pest Management (IPM) is to limit damage to the garden while protecting the environment and maintaining a healthy ecological balance in your garden between its insect pests and the natural predators of those pests.
Pests reproduce more rapidly than do predators, so maintaining a healthy population of predators assures that pest insects and bugs are kept to a minimum.
Integrated Pest Management Explained
IPM is a series of good garden practices that are used one after the other as needed.
IPM first calls for frequent inspections to discover outbreaks before they become widespread.
Inspections that turn up early pest or disease outbreaks receive treatment with hand controls—picking, crushing, washing with plain water, and the like—to eliminate the condition.
Use Non-Toxic, Environmentally Safe Controls First
Only if these hand controls fail, the next step is to treat plants and soils with biological measures. These include releasing ladybird beetles to eat aphids, applying beneficial nematodes to the soil, or spot spraying solutions containing harmless-to-people-and-pets Bacillus thuringensis (BT).
Difficult to manage pests and diseases occasionally need mild, environmentally protective controls, such as household and insecticidal soaps that smother or dissolve pest tissues.
These sequential steps usually control all but the most difficult insects and diseases.
Safe Use of Stronger Control Measures
Only the most severe, sustained outbreaks or persistant weeds should be spot treated with targeted pesticides, herbicides and fungicides.
When severe infestations and major diseases make this necessary, choose a control that lists both the pest or disease condition and your specific bulb species. Always read and completely follow all package directions for mixing, diluting, timing, frequency, and method of applying the control.
Whenever herbicides, pesticides, or fungicides are applied, wear protective clothing and a respirator. Apply the agent exactly as its package directions state directly to the infested or infected plants—avoid widespread applications—and dispose properly of any unused solution or empty containers as indicated by the manufacturer.
Quick References to Pest and Disease Control
Because pest, disease, and care problems have symptoms that differ for leafy flowering plants and flowering bulbs, you’ll find this mini-index with quick links helpful for locating the specific information for problems you see in your flower garden.