If you read my blog you know that I am not against insecticides but I am against the misuse
or unnecessary use of insecticides. With cicadas emerging, big box stores are overflowing with insecticides promising to kill periodical cicadas. This may be true. If you take a particular insecticide off the shelf and pour it on a cicada it will kill it. But these products will not ‘control’ cicadas. What are you going to do stand in your yard sprinkling every cicada you see? There are millions upon billions of them. Your dog probably stands in the yard eating them one at a time but you still have lots, right?
There is no such thing as an insecticide that only kills cicadas. They also kill butterflies, bees, and other non-target organisms. It is important that homeowners consider the risks of these insecticides (some) compared to the benefit (none). Cicadas do not last long and pose no risk to people. Insecticides do.
The other problem with trying to manage cicadas with insecticides is that they are
generally ineffective. Especially products available to homeowners provide so little benefit that the monetary cost and risk is just not worth it. If you managed to spray a whole tree with Orthene or Sevin for instance cicadas would likely colonize it again within hours or days.
Cicadas cause damage to trees when they lay eggs in twigs. They use a knife-like ovipositor (egg inserter) to insert eggs into thin twigs. This causes slits in the branch that could be 6 inches long or more. This long scar reduces plant aesthetic value but also weakens branches. Scarred branches usually break and fall to the ground or break and remain hanging in the tree but turn brown.
Trees that are very small or that you just planted this year are at risk if they get many cicada oviposition scars. Cicadas prefer skinny branches (< 0.5 inch) so if your tree trunk is this skinny it could get damaged and this could kill your tree. Other trees will shed a few
twigs and go on about their lives. You can protect trees with mesh netting to prevent cicadas from damaging them.
If you are unhappy about having cicadas on your porch or sidewalk just sweep them off. If you apply insecticide to these trapped critters (they don’t want to be on your porch) you will end up with a dead smelly pile of cicadas that you have to sweep up anyway. In addition, as you walk across the porch and sidewalk you will get insecticide on your shoes that will be carried into your house where kids and pets play on the floor. When you take your shoes off you get insecticide on your hands. Next thing you know you are eating a sandwich.
Insecticides have a place. That is to reduce economic or aesthetic damage to plants that we eat or enjoy. Insecticide applied for cicadas won’t achieve this. So save your money and wait them out or try to enjoy them.