Integrated Pest Management

Integrated Pest Management in Roses

by Mike Fuss, CR

Integrated Pest Management (IPM) is a horticultural method that is geared toward protecting the health of the environment and the gardener while supporting the health of the plants. There is relatively little information in the literature regarding specifics for roses; however, the broad principles and techniques found for other plants can be applied to roses.

The first thing that the gardener that is considering IPM should consider is how much plant damage is acceptable. This can range from “I don’t want to see any eaten leaves or any spots on my roses!” to “If the leaves all fall off, I’ll replace the roses next year.” I expect most gardeners fall somewhere in between these extremes.

So how does one proceed? Like most other cultural practices with roses, disease prevention begins even before the bush is planted by deciding to purchase roses that are more disease resistant. Then, when planting, remembering that roses like at least 5 hours of sun and finding a spot that has full sun and, if this can’t be found, trying to find a place where the sun shines early in the morning so that the evening dew doesn’t remain on the leaves. Once the bushes are planted, we can then look at the guiding principles of IPM. In general, IPM methods address insect pests; however there are cultural practices and controls that can help reduce the effects of disease.

There are four basic steps to IPM – Set Thresholds, Monitor and Identify Pests, Prevention, and Control. These steps are in addition to the basic cultural practices of proper plant selection, proper planting, fertilizing, and watering.

Set thresholds – The first step is for the gardener to determine how much pest damage is acceptable in the garden. Once this decision is made, then the gardener can proceed to learn more about what pests are affecting the roses.

Monitor and Identify Pests – At this point, it is necessary to observe the garden and identify what insects are in the garden, when they arrive and leave, and what damage they do. It is important to remember that not all insects are harmful and many are beneficial. If there is a question about an insect’s identity, a specimen brought to the Cooperative Extension Service will solve any mystery.

Prevention – The first line of defense in protecting roses from insects and disease is prevention. This begins when the site for a rose garden is chosen. Roses want at least 5 hours of sun and if there is a choice between morning and afternoon sun, the better choice is morning sun so that the overnight dew will dry quickly. Similarly, roses should be watered at ground level, not overhead, to keep the foliage dry. When planting, leave space between roses so that there is plenty of air circulation. Likewise, when pruning, leave the center of the bushes open to encourage air circulation. Not much prevention can be done regarding pests. If you plant a garden, they will come. However, there are two practices that will help. First, ensure that the garden and the area surrounding it is weed free. Some pests such as spider mites also like to live on some weeds such as ground ivy. Also keep fallen leaves and petals picked up to minimize the places for insects to hide.

Control – If monitoring reveals the need for insect control, a series of steps of increasing harshness can be undertaken. First steps can be physical methods such as hand picking and disposal or a hard spray of water from a hose. Hand picking, and pheromone traps can help control Japanese Beetles.  Aphids and spider mites can be controlled with water. For good control, the methods need to be repeated every few days. If the first step does not provide satisfactory control, an insecticidal soap spray can be used. In the case of caterpillars, Bacillus thuringiensis (BT) can be used. 

In some cases, such as midge, other methods are necessary. Here spreading a grub control product that contains Merit (Imidacloprid) and β-Cyfluthrin in the rose beds will provide some control. Look for these names in the Active Ingredients list on the bag. However, this will not provide complete control and a spray of the new growth with a β-Cyfluthrin product will offer much better protection from this insect that destroys buds before they begin to grow. 

The suggestions to help prevent disease mentioned before can be augmented by a spray program. Potentially, a material consisting of potassium bicarbonate and light oil may be helpful. However, its benefits have not been completely proven. Another spray material that contains the active ingredient Tebuconazole can be effective. In any case, the key to prevention and control of disease is to begin a spray program before any sign of disease is seen. So prevention must begin just as leaves first appear and it must continue for the growing season. Also, garden cleanliness is extremely important so keeping the garden weed free and picking up fallen leaves and petals is essential.

To summarize, IPM involves a combination of knowledge, awareness, and a series of progressively stronger techniques to keep plants healthy.