Potato flea beetle (Epitrix cucumeris)

Potato flea beetle biology & life cycle

Adults emerge and feed on the potato foliage in May and June; then they lay eggs from which larvae hatch, usually in late June. The larvae remain in the soil and feed until mid-July when pupation occurs. These flea beetles generally overwinter as adults in or on the soil in protected places. One generation is common. Potato flea beetles feed on leaves and stems, resulting in leaves with a shot-hole appearance. Flea beetles may spread bacterial pathogens and the spindle tuber viroid. Foliar damage from these beetles is seldom extensive enough to be of concern, but may indicate future damage to the tubers. The larvae feed on tubers, resulting in a pimpled surface and small brown tunnels extending 0.06 to 0.25 inch into the tuber. Similar damage is caused by the tuber flea beetle; i.e., adults feed on foliage causing small round holes, which gives the leaf a shot-hole appearance. The larvae feed on potato tubers causing surface "tracking" or small tunnels about 0.2 inch deep. This tuber injury may reduce marketability and reduces storability.

Identifying Potato flea beetle

Potato flea beetle: larvae

The larva is a slender white grub with a dark brown head and minute legs. When full-grown, it is about 5 mm in length. Typically, larvae inhabit the soil around potato roots.

Potato flea beetle: adult

Potato flea beetle adults are small , about 0.1 inch in length, metallic greenish brown to black in color. They tend to jump like fleas when disturbed. They are slender, whitish, and about 0.25 inch long when mature. The tuber flea beetle adult is also small, only about 0.1 inch long. Mature larvae are about 0.2 inch long and white with a brown head.

Potato flea beetle: management

Flea beetle populations can be reduced through regular crop rotations. Populations will tend to build up potatoes are grown repeatedly. Separation from other fields and freedom from volunteer potatoes can also help to minimise levels. New fields may be infested by adults that fly in from surrounding areas, however, in these situations, populations will tend to be lower and most beetles will be found in the field margins. On a smaller scale, removal of plant residues may limit the ability of the flea beetles to overwinter and may reduce the pest population. Earlier crops tend to be less affected than mid to late crops due to lower beetle populations and damage symptoms may be reduced or less apparent.

Monitoring for flea beetle adults is an essential step in their control. Beetle populations tend to be higher closer to the field margins, due to the tendency of adults to overwinter adjacent to the fields and the ability of adults to fly in from surrounding areas. Plants should be scouted from early emergence until plants reach 30 cm in height. Early scouting involves the examination of individual plants (sample sets of groups of 10 plants separated by 40 paces) both along the crop margin and within the remainder of the field, whereas later scouting (for plants larger than 30 cm) can be down with a sweep net. The threshold population would be 1 beetle per 60 inspected plants for early scouting and 1 beetle per 10 sweeps for later scouting.

Chemical controls can be effective in reducing egg-laying adult populations and the subsequent numbers of emerging larvae. Spraying should be based on monitoring and economic threshold populations. Chemical controls are most effective when applied early in the season. Spraying to control the adults prior to egg-laying is the only option, as spraying to control larvae is not possible.

Source: Alberta Agriculture