**Cane Beetles** is a general common name that primarily refers to several species of scarab beetles (family Scarabaeidae) that are significant agricultural pests of sugar cane (*Saccharum officinarum*), as well as other crops like corn, sorghum, and sweet potatoes. The most destructive species are often the **White Grubs** (the larval stage) of genera such as *Dermolepida* (Cane Grub) and various species of the **May/June Beetles** (*Phyllophaga* spp.). Their subterranean feeding on the plant roots and rhizomes is the main cause of economic damage.
Taxonomy and Classification
Cane Beetles belong to the order Coleoptera and are members of the family Scarabaeidae (scarabs or chafers). They undergo complete metamorphosis. While the adults may feed on leaves or flowers, the destructive stage is the **larva** (commonly called a **white grub**). The term Cane Beetle can refer to different genera depending on the region, but they all share similar life histories as root-feeding pests.
Physical Description
Adult Cane Beetles vary in appearance depending on the species. For example, the Australian Greyback Cane Beetle (*Dermolepida albohirtum*) is robust and light brown to gray, about 20–25 millimeters long. Many other adult pest species are smaller, shiny brown or black beetles. They are stout-bodied, with hardened wing covers (elytra) and clubbed antennae.
The larvae, or **white grubs**, are the most recognizable stage. They are large, creamy white, soft-bodied, and C-shaped, with a brown head capsule and three pairs of legs near the head. They can grow up to 50 millimeters long and are typically found coiled in the soil near the plant roots. Identifying the exact species often requires examining the pattern of hairs and spines on the raster (the tip of the abdomen).
Distribution and Habitat
Cane Beetles are found in agricultural regions globally, especially where sugar cane, grasses, and turf are cultivated. Specific pest species are highly localized. For instance, the major cane pests are found in the sugar-producing areas of Australia, the Caribbean, and the Americas. Their primary habitat is the soil of crop fields and pastures, where the larvae live and feed for months or years on the root systems of host plants.
Behavior and Life Cycle
The life cycle of a Cane Beetle species can span from one to three years. Adults typically emerge in large numbers at the start of the summer or rainy season (hence the name May/June Beetles for some species). Adults are often nocturnal, attracted to lights, and mate in the field. Females deposit eggs deep in the soil, often near the base of host plants.
The **larval stage** is the longest and most destructive. The newly hatched grubs are small, but they grow through three instars, continuously consuming the roots and rhizomes. They typically move deeper into the soil to overwinter or pupate, then emerge as the next generation of adults.
Feeding and Damage
The **larval feeding** on roots and rhizomes is the primary economic damage. In sugar cane, the grubs chew on the underground portions of the stalk and the root system, inhibiting the plant’s ability to absorb water and nutrients. This leads to **stunted growth**, yellowing leaves, and severe **lodging** (falling over) in the field. Infested cane fields show patchy growth, and entire stalks can easily be pulled from the ground due to the severed root system.
Adult feeding on leaves, while sometimes heavy, is generally considered minor compared to the root destruction caused by the grubs. Economic losses are severe, especially in ratoon (regrowth) crops where root damage from the previous year is compounded.
Management and Prevention
Control focuses on targeting the vulnerable larval stage in the soil.
- Chemical Control: Systemic insecticides are applied to the soil, often at planting or ratoon time, to be taken up by the roots and poison feeding grubs.
- Biological Control: The use of **entomopathogenic fungi** (*Metarhizium anisopliae*) or **nematodes** that attack the grubs in the soil has proven highly effective in integrated pest management programs, particularly in sugar cane.
- Cultural Control: Deep tilling or plowing of the soil during periods when larvae are close to the surface can physically kill them and expose them to predators. Trapping adult beetles with light traps during emergence can also reduce egg-laying in small areas.
Conservation and Research
Cane Beetles are major agricultural pests. Research focuses heavily on the development and large-scale application of **biological control agents**, particularly fungal spores, to achieve long-term suppression of white grub populations in the soil with minimal environmental impact. Efforts are also ongoing to breed cane varieties that are more tolerant or resistant to grub feeding.