Treating for Plant Pests and Diseases

When you do need to treat for plant pests and diseases, there are a few best practices to follow. First, avoid using sprays when bees are present. Early morning and late evening are better. You should also refrain from spraying on windy days to prevent drift, and only apply sprays after plants have finished flowering. If you must treat flowering plants, remove all flowers until the chemical is no longer present. Lastly, always remember to read and follow the instructions on any pest control products you choose to use.

In addition to being mindful of the ways in which you manage plant pests and diseases, it’s also important to provide safe forage for bees by selecting plants that bloom throughout a long season. Hundreds of flowering plants are good food sources for bees—including Salvia, Monarda, yarrow, Echinacea, goldenrod, sunflowers, Aster, and honeysuckle. You can also provide support with common herbs like lavender, thyme, and oregano. Flowering cover crops, such as buckwheat and clover, are very attractive food sources (clover can also be added to lawns or used as a lawn substitute). Even weeds, like dandelion and blackberry, can be an important food source for bees. If you are concerned about sprays that may be hitching a ride on your new plants, you can remove their flowers the first year, which has the benefit of rapidly increasing the size of the plant, creating a much bigger show and much more bee food the next year!

BEST PRACTICES

Make mindful decisions about what you plant. Some plant species have few pests, and disease-resistant varieties of others (like roses) are available. Taking care of disease-prone plants is hard work, expensive, and occasionally difficult without potentially dangerous products. Why not replace a problem plant with something beautiful and rugged and skip the sprays?

Healthy plants resist insects and disease better than plants that are struggling. We can help you choose the appropriate type of fertilizer and watering schedule for your plants. Stop by our Information Desk for specific information.

Some products are generally safer than others, but still aren’t 100% safe in every situation. A Best Practices or Integrated Pest Management (IPM) approach first asks whether it’s necessary to do anything at all (often it’s not!).

For example, aphids can often be dealt with by a healthy blast of water from the hose, rather than the use of an insecticide. Likewise, if you’re having an issue with spider mites on your roses, for example, consider using a soap solution before applying a powerful systemic. Beneficial insects like ladybugs and lacewings can also be introduced to combat pests at certain points throughout the year.

If treatment is called for, choose the lowest-impact product first—biological, organic or synthetic—taking into account consequences not only for bees, but also for people, pets, ground-water, run off, and many other factors. For instance, insecticidal soap and horticultural oil residues on plants are mostly safe for bees, pets, and people—but spraying them directly on bees can be fatal. It can also be hard on aquatic life if used near streams and ponds.

Our long, dry summers mean bees often have to spend time getting to water. Shallow pans or bird-baths with rocks for resting on can be a great place for bees to drink!

Small producers are an excellent alternative to the commercial bee industry. Commercial bee-keeping is intricately tied to agricultural mono-cropping, and as currently practiced, leads to poor bee nutrition and spreads disease throughout the country. Locally kept bees tend to feed on a larger, healthier variety of food sources and receive better care.

Bee-keeping can be a rewarding hobby, as well as a source of honey. Even if you don’t have the time or room to keep honey bees, you can support mason bees or other native pollinators. Portland Nursery has several classes each year on bee-keeping and mason bees. You can also contact the Oregon State Beekeepers Association at 503-657-5399

LEARN MORE

Though native bees and other insects are incredibly valuable pollinators, honey bees provide most of the pollination for hundreds of our favorite food crops. The arrival of the Varroa mite in the 1980’s dealt bees a hard blow. Then in 2006, sudden mysterious hive losses began to occur. Scientists coined the term Colony Collapse Disorder (CCD) to explain the phenomenon.

Since the appearance of CCD, scientists have investigated many leads. They have concluded that there is no single cause for bee declines and that all the following factors play a role:

Pests and Pathogens
- Varroa mite: The single worst honey bee pest. Reproducing quickly and easily, this mite can kill and weaken bees. Mite wounds are a huge vector for the spread of bacteria, fungus, and viruses.
- Nosema ceranae: This recently arrived fungus is the cause of some colony collapses, and interferes with the bees ability to digest and absorb food. It also weakens immunity to toxins and certain diseases.
- European Foulbrood, American Foulbrood, Chalkbrood, and dozens of other viruses have also played a role.
Pesticides
It should come as no surprise that products intended to kill insects can kill honeybees. The spotlight has recently been focused on a class of insecticides called neonicotinoids, but hundreds of pesticides—both synthetic and organic—can also be deadly to bees.
Nutrition
Most hives service mono-crop industries (60% of all hives are taken to California to pollinate the almond crop). The lack of food diversity in these settings contributes to poor nutrition, and supplemental food provided while moving hives and in winter is often low-quality. Changes in forest and land management have also eliminated plants that once served as alternate food sources.
Genetics
North American bees descend from a very small gene pool, and very little effort has gone into breeding for traits other than docility and honey production. Breeding for disease and mite resistance, tolerance of local climate, and hygiene behavior is needed.

For more complete information, download the USDA report on Honey Bee Heath or visit the Horticultural Research Institute’s website.

Please remember, while these chemicals have proven harmful to bees, the manner, timing, and reasons for their application must also be considered. When you must use pesticides, be mindful of what, when, and how much you use to minimize the damage to bees and other beneficials. Spraying after the sun has gone down will help minimize exposing beneficials to chemicals. Never spray a plant in bloom! That is when the plant is most attractive and beneficials are most present, increasing the chance of harm.

Synthetics
Acephate
Carbaryl
Carbofuran
Chloropyrifos
Chlorothalonil
Chlothianidin
Cypermetherin
Diazinon
Dinotefuran
Endosulfan
Fenthion
Imidacloprid
Malathion
Methidaphion
Methamidophos
Methomyl
Permethrin
Thiomethoxam

Please remember, while these organics have proven harmful to bees, the manner, timing, and reasons for their application must also be considered. When you must use pesticides, be mindful of what, when, and how much you use to minimize the damage to bees and beneficials. Spraying after the sun has gone down will help minimize exposing beneficials to chemicals. Never spray a plant in bloom! That is when the plant is most attractive and beneficials are most present, increasing the chance of harm.

Beaveria bassiana
Copper Sulfate
Diatomaceous Earth
Horticultural Oil
Insecticidal Soap
Pyrethrins
Rotenone
Sabadilla
Spinosad