We are trying to establish a permaculture farm in northwestern New York. We have very sandy soil, and everything we grow is ideal food for the rose chafer beetle. We first noticed them last year and tried to fight them. We thought we had controlled them, but instead they had just finished their life cycle. We were infested last year, so each year it is going to get worse. I really don't want to use pesticides. These beetles are known to be poisonous to poultry and other birds. The only suggestions I have found are to use row covers and monitor plants from May through mid July, hand pick if not infested, place bait traps every 100 feet, or release parasitic nematodes. I do not know the cost or what type of traps Ohio State is suggesting, but the nematodes seem to be running $99.99 for 50 million, and we would need 6 of those just for the garden.
On smaller plants (garden vegetables, berries, espalier trees, etc), you can use a floating row cover to prevent the adults from feeding. Without pesticides you will be limited, but you may end up boosting the crop enough through pest prevention to cover the cost of the cover.
Here you are also limited without the use of pesticides, but you have a lot more cost effective options.
- Cultivation of the soil starting as soon as the soil dries in the spring, up until the time in June that the beetles fly, has been highly effective for me personally. This method is hard in no-till areas (obviously) where mulch is used to cover the soil.
- Hand picking the beetles can help when the numbers are small, even for large applications.
- Nematodes can be used in areas where cultivation is not sensible, used as a soil drench to fight larvae/pupae.
- Traps, especially white ones (made for Japanese beetles, can be effective if the right bait is used. The traps are reusable, and you can get them for affordable amounts (example rose chafer bait).
All together you should be able to manage the beetles using these methods, even if you don't totally destroy them.