I follow the Integrated Pest Management (or IPM) approach to controlling pests and diseases in my garden.
For more details about IPM, please see my earlier article earlier on IPM.
To review, there are 5 steps to IPM.
- Walk around your garden on a regular basis inspecting your plants for insects or their damage.
- Determine what your acceptable level of pest damage is.
- Consider all of the options available to control the pests once the level has been reached.
- Choose the least toxic solution that will solve the problem.
- Continue to inspect your plants on a regular basis.
Insects that are most likely to affect roses.
These insects feed by sucking juices from the plant. Flowers may also be affected if the aphids attack the buds. When checking for aphids look for honey dew, a clear sticky waste product deposited by the aphids. The honey dew will usually attract ants which is a good sign that aphids are present.
Beneficial insects such as lace wings and lady beetles are effective in controlling aphids.
A strong stream of water is a good way to knock the aphids off of the plants. Do this early in the day so that the foliage has time to dry before dark.
Insecticidal soaps are also very good and far less toxic than other chemicals.
Chemical controls include pyrethrums, malathion, acephate (orthene), chlorpyrifos (dursban) and diazion.
These creatures are very small and hard to see. A magnifying glass is a valuable tool when looking for mites. These also are sucking insects. You can usually see yellow stippling in the areas below where the mites are feeding. You may also see small webs on stems and leaves. Place a sheet of white paper under a branch, shake the branch vigorously, the mites will fall onto the paper making them easy to see.
Insecticidal soaps and horticultural oils are effective in controlling mites.
Dicofol (kelthane) is a chemical that is effective in controlling mites.
This is a type of beetle that is usually found in sandy areas.
In June the adults begin to feed on a wide variety of plant including roses. Leaves are usually skeletonized with veins and a small amount of tissue left behind.
Carbaryl (sevin), methoxychlor, or permethrin are effective chemical controls.
This is a tiny fly that lays its eggs in the shoots and buds on a rose. The larvae are about 1/16th of an inch in length.
If you detect misshapen or blasted blooms you more than likely have a midge problem. The shoots and buds will turn brown, and then black.
Examine the buds with a magnifying glass; look for small whitish larvae between the petals at the base of the bud.
Prune out the affected buds to remove the pests.
Midge infestations are usually seen after July.
Systemic insect ides are usually the best control. Acephate (orthene), anddimethoate (cygon 2_E) are systemic. Diazion is a non systemic is also an option but not as effective as those previously mentioned.
This pest is widespread and feeds on many plants including roses. This pest in the grub stage will feed on the roots of various plants.. The Japanese beetle also skeletonizes the leaves leaving only veins and very little leaf tissue.
Hand picking, By noticing when the first adults arrive on a property, you can pick off and destroy these scouts that attract additional pests. The adults are less active in the early morning or late evening. They can be destroyed by dropping into a container of soapy water.
Chemical controls, midacloprid [Merit] and halofenozide [MACH2]), applications in June and July have sufficient residual activity to kill the new grub populations as they come to the soil surface in late July through August.
Rose Stem Sawfly
Rose Stem Girdler.
These are a couple of insects whose adults are not usually seen. They lay there eggs on the canes and the larvae bore into the stems. Its feeding within the stem prevents water and nutrients from moving up the stem thus killing it. Sometimes the stem may swell below the dead area.
There are no chemical controls for borers.
When you notice damage, prune out the stem, below the damage.
Whenever you prune your roses, seal the freshly cut end with a dab of Elmer’s glue. This will prevent bores from entering the stem through the cut.
Leaf Cutter Bees
Folks usually panic the first time they see damage of the leaf cutter bee.
The bees cut out a circular hole in the leaves. It looks like someone has taken a cigarette and burned several hole in the leaves.
The bees actually do no damage to the plant whatsoever. They are cutting out a piece of the leaf tissue to line their nests with.
No action is needed in regard to leaf cutter bees.
Damage from leaf cutter bees
These are probably the most common pests that you will see on your roses. If you see something other than these, take a sample to your county extension office, they will help you identify it and suggest control measures.
The next installment of Growing Roses from A-Z will be on diseases that affect roses.
Photos courtesy University of Minnesota Extension