To control Japanese beetles, remove the adult beetles manually, and apply pesticides to the affected plants. To eliminate beetle larvae, apply beneficial nematodes to the soil. Beetle control requires persistent efforts during the summer months if the infestation is severe.
- Manually remove the beetles
To manually remove the beetles, shake the plants gently over a bucket of soapy water each morning, or handpick the beetles off the plants. Place each beetle in soapy water after removing it from the plant.
- Apply pesticides to the plants
Pesticides, including neem oil or pyrethrins, should be applied to plants according to the instructions on the product packaging. Powdered insecticides should be reapplied after approximately five days, while pyrethrin-based insecticides typically work for up to two weeks after the initial application. When applying pesticides to edible plants, such as raspberries, choose a product that is recommended for use on food crops.
- Reduce grub populations
Beneficial nematodes, such as Heterorhabditis, are used to kill Japanese beetles in the larval stage. To apply nematodes, dilute the product with water according to the directions on the packaging, and drench the soil in the affected area using a garden sprayer. Nematodes should be applied on a cool, cloudy day for optimum results.