By Stephanie Butcher, Coweta County Extension Office
(In case you missed this before the July 4th holiday, here’s a republish of Stephanie Butcher’s column on eliminating bugs from your backyard flowers.)
Question: A shiny green bug is eating my roses. I applied an insecticide, but it didn’t work. How can I get rid of this pest? It’s destroying my beautiful flowers.
Agent: Proper identification of an insect is important, especially when you are wanting to get rid of it.
Not all insects are made the same. Some insects have chewing mouthparts, some have piercing/sucking mouthparts and still others are borers. That’s why there are so many different insecticides out there.
Although it can be tempting to run to the store and apply the first thing you find with a bug on the label, the first thing you should do is get a positive identification of the pest. Not all insecticides work on all insects. Make sure that the product you choose is labeled for your particular pest.
It sounds like you have Japanese beetles, but to be sure, you can bring a sample of the insect to the Coweta County Extension office (in a sealed container preferably in rubbing alcohol) or you can take a picture of the insect and email it to email@example.com.
Adult Japanese beetles, like the ones shown in the image from my own knockout roses, are chewing insects. They live four to six weeks, lay eggs (mostly in mid-August) and die. If the soil is sufficiently moist like it is right now, the eggs will swell and produce larvae in about two weeks. The rest of the year, the beetles live underground in a larval stage feeding on the roots of grass and other plants before maturing into adult beetles in the summer.
Japanese beetle larvae are plump, C-shaped white grubs often seen in the spring when garden soil is first tilled. The grubs need soil moisture to survive the winter. Frequently irrigated lawns and landscapes tend to have higher grub populations.
Controlling the grub stage generally has little effect on the overall damage caused by adult beetles since adults can fly into your landscape from up to a mile away. Most homeowners rarely have grub populations large enough to cause damage to home lawns. Treatment may be necessary if more than five to ten grubs per square foot are present in lawns. Late summer and early fall insecticide applications are most effective at killing young grubs.
The key to controlling Japanese beetles is to catch them early in May or June. For small infestations, you can handpick or knock adult beetles off plants and drown them in soapy water. This is an effective control option for managing small infestations and preventing them from attracting more beetles.
If your life is crazy busy like most of us, and you don’t notice these pests until half of your rose bushes are infested in July, then they can be controlled with carbaryl, which is sold under the trade name, Seven. Read and follow the pesticide label’s application rates and safety precautions.
If you don’t like the idea of using a spray, then you can use traps. Phermone traps work, but they tend to attract more beetles to the area than would normally be present. Don’t put them in your garden or near your ornamentals. Place them in an area that will lure beetles away from your prize plants.
For more information about common landscape pests and how to get rid of them, call the Coweta County Extension office at 770-254-2620 and ask for the publication, “Control of Common Pests of Landscape Plants”.
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Photo: Japanese Beetles