By Darren Morgan
Even the most hands-off and bug friendly gardener will sometimes need to make pest control decisions. But even while saving our plants from voracious attacks, we want and need to keep an eye on protecting the good guys — beneficial bugs, particularly pollinators. We can have happy plants and a healthy ecosystem if we make good choices, but there’s more to it than the pesticide selections we buy.
Awareness
There really is no substitute for spending time with your plants, and seeing what is happening. Plant pest awareness has three components:
- Plant knowledge — Know your plants’ needs, what healthy looks like, and what they need to grow. Learn their common pest and disease challenges.
- Pest knowledge — Not all the bugs you see on your plants are bad — many are neutral or even beneficial. Identify insects seen, so you can determine if they are a problem and what control measures are best for them. Many local garden centers welcome samples for plant and pest identification.
- Product knowledge — Pesticides can be complicated, and products and labels do change. Read all appropriate labels, and get help or recommendations from nursery professionals if needed.
Intervention and prevention
The best pest intervention is prevention. Healthy plants are less likely to have pest infestations. Give your plants the care they need to thrive, including appropriate sun or shade, fertilizer, and watering.
Keep weeds controlled, as they often harbor pests that can move from weeds to desirable plants.
In some cases, manual control of pests is practical. Slow moving or immobile pests such as aphids and scale insects can be reduced or even eliminated by pruning or pinching out infestations. On the other end of the spectrum, plants that are heavily infested may be best culled out and removed, so their problems don’t spread more widely.
Most mite and insect pests will require some form of pesticide to control well. All insecticides are not equal. Some provide better control on specific pests, and some are significantly safer for non-target insects such as bees, butterflies, and other beneficials.
Timing matters too. When pesticides are warranted, apply right away before the problem gets worse. A few insect pests can even be prevented with carefully timed sprays.
Avoid applying any pesticide, even relatively safe ones, to plants that are in bloom. This is even more important with longer-lasting insecticides. It’s important to know how long the product is active, and to avoid applying it if too close to flowering.
It’s better to apply pesticides in the evening. Many pests are more active at night and most of our pollinators go to bed early, so evening applications are safer and can be more effective.
Safer pesticides
Insecticides are designed to kill insects, but some are safer than others. For pollinator safety, use products that are either very targeted to specific types of insects, or ones that have very short durations. Read the label — bee safety cautions are found in the environmental precaution section. Learn active ingredients, as the same product is often sold under many different brand names, and similar looking and sounding brands can have very different ingredients.
Some pesticides to be cautious of:
- Systemic insecticides. This group includes the neonicotinoids such as imidacloprid and dinotefuran, as well as acephate and disulfoton.
- Carbamates such as Carbaryl, which are long lasting and very toxic to bees.
- Pyrethroid insecticides. Though in many ways safer than other pesticides, pyrethroids are highly toxic to bees and relatively long lasting. Pyrethroid names end in -thrin, and include beta-cyfluthrin, bifenthrin, cypermethrin, deltamethrin, lambda-cyhalothrin, permethrin, and pyrethrin.
Some safer alternatives:
- Horticultural oils. Though they can have some negative impacts, these are minor and short-lived — and oils aren’t usually used on plants in flower. Often used as a preventative.
- Insecticidal soap. May also be listed as potassium salt of fatty acids. Very safe, non-specific control with very short duration. Insecticidal soap will affect all insects that come in contact, but only until dry.
- Biological insecticides. BT (Baccilus thuringensis) is the most common and best known, but other bacterial, fungal (Metazarum anisopliae, Beauveria bassiana), viral (Cydia pomonella) and beneficial nematodes are sometimes available. These are very specific targeted controls for specific pests, quite safe for other bugs.
- Bacterial fermentation insecticides. Spinosad is less selective than the biological controls, but still targets a narrow range of pests. It is also longer lasting and can be carried on pollen, so do not apply in bloom.
- Sulfur. Used primarily for disease control, but has some insecticide uses, particularly for mite control.
- Neem. Listed as neem, neem oil, hydrophobic extract of neem oil. Non-specific, but is only toxic when ingested, which dramatically limits risks to beneficial insects.
Insect challenges will always be a part of growing plants, but with a little thought and care we can help ensure that our gardening behavior encourages and preserves a healthy ecosystem.
Darren Morgan is a lifelong Oregon resident and the nursery manager at Shonnards Nursery, Florist, and Landscape in Corvallis, Oregon. He has worked in the nursery industry for 36 years.