Chinese Rose Beetles: A Life in the Dark
By Glenn I. Teves, Extension Agent, UH CTAHR
The Chinese Rose Beetle, Odoretus sinicus, is one of the most insidious and troublesome garden and yard pests due its wide host range. It can feed on over 250 species of plants, including taro, beans, corn, eggplant, okra, banana, cacao, ohia lehua, heliconia, and roses. First reported in Hawaii in 1891, the Chinese Rose Beetle is found throughout Asia and the Pacific.
Due to our strange weather this summer, we’ve been having more than our share of Chinese Rose Beetles. Its signature holes in leaves looks like someone took a buckshot to your plants, and its damage can stunt and even kill plants. A golden beetle the shape of a Volkswagen Beetle, the Chinese Rose Beetle is nocturnal, and will start moving around just after dark, and can usually be found finishing its meal from the night before. They emerge from their hiding places around dusk and will feed for a couple of hours, then retreat to their abode, although they will occasionally feed in overcast weather.
During daylight, they will hang out in shady or dark surroundings at the base of the plant, in leaf litter or organic matter, or more likely just under the soil surface, especially on the edge of a wet area. Eggs are laid in the soil and are usually found in the top 1 ½ inches of soil, and they usually take 100 days to go through their life cycle including three larval stages and a pupa or grub stage. If you dig a little below the surface, you usually can find a large white grub.
Outdoor lights have been used to control them in rose plantings around residences at night, because bright lights repel them. If you venture outside at night in a Chinese Rose Beetle infested yard with a bright head lamp, they will attack the light and your face, and swarm around your head. More recently, low-intensity portable solar-based light-emitting diodes or outdoor solar lights have been used to deter and control them in cacao field plantings. When using solar lights with illumination intensities of 5 lux, Chinese Rose Beetle damage was decreased by 75 percent. A take-off from this idea is drilling a hole in a bowl, attaching it to the stem below the light, sealing it so it doesn’t leak, and filling it with soapy water to capture the beetles.
Controlling this pest has always been a challenge, with systemic insecticides such as Sevin as the most common control method. At low populations, picking them off at night is viable option. For low-growing plants that don’t require cross-pollination by insects or bees, covering fields or rows with cloth barriers such as Remay cloth has been successful, and was employed on a large scale by seed companies on Molokai to grow soybeans. For more information on the Chinese Rose Beetle, you can access: extento.hawaii.edu/kbase/crop/Type/adoretus.htm