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Die Welt

by Nanette Londeree, Master Rosarian

The range of pests that attack roses is broad, and varies garden to garden. What might be a pest in one environment may be of negligible concern in another. While one dictionary definition of a pest is “an annoying person or thing; a nuisance”; the relevant definition for your roses is “an injurious plant or animal, especially one harmful to humans.” The term pest is most often used in reference to living organisms that are detrimental to humans, animals, plants or even the environment. They can range from the large, highly visible type like deer, to those that cannot be seen by the human eye like bacteria and viruses. The primary pests that plague roses in our area are insects, mites and fungal diseases.

In our series “What’s Bugging You”, we focused on methods for identifying the pests that frequent your garden. Now, if your sleuthing has identified any pests you’d like to manage, the next step is to understand options for pest management and select one that is right for you. Ideally, the method of pest control you choose is easy on the gardener, the pocketbook and the environment. In this series, we’ll explore methods and products available to the rosarian, providing you with some “Rx for Healthy Roses."

IPM Basics

Integrated pest management, abbreviated as IPM, is an approach for controlling pests using the least toxic methods available; pest management decisions are based on need and effectiveness rather than on a specific schedule. According to the U.S. Environmental Protection Agency (EPA), IPM is “an effective and environmentally sensitive approach to pest management that relies on a combination of common-sense practices. IPM programs use current, comprehensive information on the life cycles of pests and their interaction with the environment. This information, in combination with available pest control methods, is used to manage pest damage by the most economical means, and with the least possible hazard to people, property, and the environment.”

IPM Pyramid

An IPM program involves:

  • Determining how much damage you can tolerate (action thresholds)
  • Observing the garden for pests (monitoring)
  • Diagnosing the problem (identification)
  • Implementing a pest management strategy (prevention and control)
  • Evaluating effectiveness

    The key concept to keep in mind is that all pests live in an environment of checks and balances. Every action (or inaction) you take will affect the checks and balances. By observing these causes and effects, you can begin using them to your advantage.

    Why Use IPM?

    With so many available chemical methods of managing pests, why use an integrated pest management system? Simply put, IPM helps you manage pests - insects, plant diseases, weeds, and more - in an integrated manner, using holistic, ecologically based methods that help keep health, economic, and environmental risks as low as possible. Once you get into the habit of it, IPM is really quite easy and makes lots of environmental and economical sense. It is gentler on the environment and protects the health and safety of people, pets and property.

    Developing a Pest Control Approach

    When determining what type of pest control approach or strategy you want to take, consider:  

  • Pesticide residue - very little of the pesticide actually reaches the target pest. What happens to the rest of the pesticide? Will other household members or pets come in contact with the residue? How long does the pesticide remain active?

  • Pest resurgence - most pesticides kill the predators as well as the pests. Because pests can usually rebuild populations faster than the predators, it is very common to see increases in pest levels (resurgence) a few weeks after applications of pesticides.

  • Secondary pest outbreaks - treatment of one pest may result in an increase of another pest by accidentally killing the beneficials that had the secondary pest under control.

  • Health hazards - will people, especially children, or pets come in contact with your roses while the pesticides are still active?

  • Environmental concerns - any pesticides used on your roses or garden can contaminate groundwater or travel through storm drains and contaminate creeks, lakes, and rivers. Keep pesticide use in your garden; avoid drift onto neighboring properties, especially gardens containing fruits or vegetables ready to be picked.

  • Social factors - is your neighborhood and town supportive or intolerant of pesticide use? Will frequent spraying of your roses cause others to avoid growing roses?

  • Cost factor - what is the economic cost of a spraying or beneficial release? What benefit will it provide versus waiting for natural checks and balances to control the pest?

  • Appearance problems - treating rosebushes with imported beneficial insects will still leave the roses with insects. The blooms may be unusable in a rose show without extensive cleanup. Likewise spray residue (whether "synthetic chemicals" or non-toxic antitranspirants) can be both unsightly and can lead to disqualifications at a rose show as a "foreign substance."

    Pest Control Options

    Follow the progressive treatment approach beginning with the least toxic method; cultural, mechanical, biological and finally, chemical methods. There is also the “do nothing” method, where the damage from the pest is either so low, or the cost / risk of an effective control measure is so great, that no action is needed.

  • Cultural methods - selecting plants with known disease resistance, maintaining healthy and vigorous plants through proper soil health and cultivation, watering, fertilizing, pruning, mulching and good garden sanitation.

  • Mechanical and physical methods – manual handpicking insects, pinching, washing with water, pruning, and removing dead leaves and twigs; physical barriers like fencing for deer, planting in wire for gophers, traps - pheromone, bait, sticky or light types, and anti-transpirants for fungal disease.

  • Biological methods - improve the habitat for natural enemies – predatory insects such as ladybugs, soldier beetles and green lacewings, and parasitoid insects that lay eggs in pests. Create or enhance habitats for birds, lizards and toads. Utilize microbial controls - pathogenic microbes like BT (Bacillus thuringiensis) for treating caterpillars.

  • Chemical methods - start with the least toxic chemicals like horticultural oils, insecticidal soaps, plant derived products like neem seed extracts, and pyrethrum. Where possible, use selective pesticides that only effect a limited population of pests and less likely to injure beneficial insects. Broad-spectrum chemicals are non-selective and can kill anything they contact, resulting in increased pest populations, and as such should be used only if all other options fail.

    In the coming months, we’ll look in more depth at options for cultural, mechanical and physical, biological and chemical methods of managing major pests of the rose garden, giving you plenty of “prescriptions (Rx)” for healthy roses.

    Photo of ‘Die Welt’ and the diagram are by Nanette Londeree

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    Last Modified: 08/06/2013