My chrysanthemums are being attacked by a reddish brown beetle which buries itself in the soil until after dark, then proceeds to devour the foliage at night. What can I do? -Dorothy
It sounds like your mums are being attacked by Asiatic garden beetles. These nocturnal beetles are about 3/8” long with a reddish-cinnamon color. They emerge in mid to late summer to feed on the leaves and flowers of many types of plants, including chrysanthemums.
Like Japanese beetles and other garden beetles, Asiatic garden beetles are difficult to control once the adults have moved in for the season. Here are some things to try:
- Manual control: This means hand-picking the adult beetles and drowning them in soapy water. Asiatic garden beetles can be caught by hunting them in the garden at night, or by catching them as they congregate on lit-up windows and screen doors.
- Biological grub control: Asiatic garden beetle larvae fall into the common category of “white grubs.” If you have a serious infestation, your best bet may be to work on controlling these grubs, which hatch and feed underground in the early spring before emerging as adult beetles in midsummer. Several biological controls are available to control white grubs in turf grass, including predatory nematodes and bacterial agents. Plow up your vegetable and flower gardens as early as possible in the spring, to expose the grubs to hungry birds.
- Chemical control: While there are some pesticides registered for control of Asiatic garden beetles, chemical controls are generally considered pretty ineffective against adult beetle populations. They also harm other insects and birds, and can be harmful to humans and pets as well. If you choose this route, read the labels carefully to get the product that will create the least collateral damage.
- Protect your garden: Use row covers to protect vegetables from feeding adults in late summer. Handpick any feeding adults you find. In the fall, clean up your garden and plow under (or compost) garden debris, to reduce populations of overwintering eggs. Keep your lawn healthy and thick to reduce grub infestations.
- Asiatic Garden Beetles (University of New Hampshire Extension)
- Photo of Asiatic Garden Beetle (Tree of Life Web Project)