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There are not a lot of bugs that are going to bother your roses, but the ones who do, can really get “under your skin”. Keep in mind that with any pest control program the idea is to work with nature to keep a balance, not to eradicate every living creature in your garden.
Like fungicides you have choices of “systemic” and “contact” with different modes of action. For this article we will focus on using products that control aphids and thrips.
1. Systemic insecticides – systemic products are absorbed and work from inside the plant making the plant toxic to the insect that eats it. These insecticides can be applied with fertilizer, in a soil drench, or applied foliarly.
2. Contact insecticides – contact products are sprays that are applied to the leaves and blooms of the plants. If insects are present during the time of application or if they ingest leaves that have been sprayed, they will be affected.
3. Natural or Organic – like all plant protectants there are many products that are listed as organic or natural. Neem and other plant based oils are often used in these products. As with all products read the label carefully to see what insects these products control.
Aphids are one of the common insects that we work against. They grow huge colonies that suck the juices out the stems and buds. The good news is that the damage that they do is limited and they should be relatively easy to control. Most systemic or contact control products including insecticidal soap should lower the aphid population. In most cases it takes repeated applications to get them off of your bushes completely.
Thrips are tiny insects that live inside your rose buds and suck the water out of them leaving brown spots on your blooms. Systemic insecticides do not help with control because the vascular system of the leaf is different from that of a petal and the flowers do not get enough insecticide in them to help. Use a contact product that is labeled for thrips and spray it into the bloom getting it all the way down to the base of the bloom whenever possible.
One note about broad spectrum insecticides such as Sevin- broad spectrum insecticides will get the job done every time. They are a great last resort. However, they do tend to kill beneficial insects along with the bad guys which can cause problems down the road. They will also quickly get rid of any butterflies or bees that you may want in your garden. We strongly recommend limited use of broad spectrum insecticides.
I know what you are thinking. What about Japanese Beetles? They are the bane of my rose growing life! The discussion of Japanese Beetles is sufficient to warrant its own article next month. We know that we will see them in June.