The decision to use chemical control for pests never should be taken lightly. Both organic and synthetic pesticides have a certain degree of risk to humans, animals and the environment associated with their use. Risks can be reduced by reducing the amount of organic and synthetic pesticides applied.
What pesticides are available to control Japanese beetle?
Milky spore is an organic insecticide that uses a bacterium, Bacillus popilliae, as the killing agent. Milky spore disease first was observed infecting Japanese beetles in the 1920s. It will attack and kill some Japanese beetle. Affected beetles will spread the disease when they die, and the bacteria will remain in an area for several years. The bacterium is most effective when used in large areas citywide, not as successful when just used in a yard.
Pyrethrum, which comes from a species of chrysanthemum, is the most commonly used organic pesticide. This chemical disrupts insect nerve impulses. It is fast-acting, very effective and toxic to beneficial insects as well as pests like Japanese beetles. It is degraded quickly by sunlight, so is only toxic for a very short time.
Pyrethroids are synthetic pyrethrins altered to break down less quickly. A number of pyrethroid insecticides have been created. Permethrin is one that is available in many products from a number of companies. Similar to its organic cousin pyrethrum, Permethrin also is fast-acting, highly effective and toxic to beneficial insects as well as pests like the Japanese beetle. But unlike Pyrethrum, it is not systemic, so it will not be taken up by the plant's vascular system.
How can I safely apply these pesticides?
Always wear the recommended personal protective equipment. I wear rubber boots, vinyl gloves, a hooded Tyvek suit, goggles and a respirator when applying pesticides. It is hot and I look silly, but I am reducing my exposure to the chemical.
I find organic pesticides to be scary, not because they are more or less toxic than synthetic pesticides, but because there is this public perception that organic is safe. Nature has produced some pretty nasty poisons. Always read and follow the label, because it is a legal document and not following it is breaking the law. The label also provides information on how to safely and effectively apply the chemical.
How can I protect beneficial insects if I choose to use an insecticide?
Japanese beetles love rose buds, but so do pollinators like bees. Most pollinators forage during the day, so to reduce risk, make applications early in the morning or at dusk.
Japanese beetles have been skeletonizing linden trees across the city. The linden tree in the SMART Garden has been treated with an insecticide, but it was treated after the linden was done flowering to reduce the risk to pollinators.
This is not a complete list of available options. Do some research, read different opinions and pay attention to the results. The final component of a pest management program is to assess the effect of the management strategy.