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Ministry of Agriculture, Food and Rural Affairs

Potato Stem Borer

Potato stem borer Potato stem borer damage Potato stem borer damage Potato stem borer damage
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Beginner

Scientific Name
Hydraecia micacea

Identification
Mature larvae are dark to light pink and about 3.5 cm long. Adults are brown moths that are active during August and September.

Often Confused With
European corn borer

Period of Activity
In late May or early June, the larvae move from grass stems in search of larger weeds or cultivated crops such as potatoes.

Scouting Notes
Fields should be monitored shortly after emergence. In late May, early June the potato stem borer larva migrates to potato fields. Wilted plants near border rows early in the season are usually infested with the stem borer. Affected plants have a hole at the base of the stem.

Thresholds
Not established.

Advanced

Scientific Name
Hydraecia micacea

Identification
Mature larvae are dark to light pink and about 3.5 cm long. Adults are brown moths that are active during August and September.

Often Confused With
European corn borer

Biology
Life stages: eggs, larvae, pupae, adults.

Female moths lay eggs from August to September on grassy weeds in and around potato fields. These overwintering eggs begin to hatch in late April or early May, and the small larvae bore into the grasses. By late May or early June, the larvae outgrow the stems of the grasses and move on in search of larger weeds or cultivated crops such as potatoes. Larvae usually infest plants in border rows close to grasses where the larvae first fed. Larvae bore holes close to the base of the stem to penetrate young plants. Then, larvae feed on stem tissue. Infested stems wilt, collapse and eventually die.

Period of Activity
In late May or early June, the larvae move from grass stems in search of larger weeds or cultivated crops such as potatoes.

Scouting Notes
Fields should be monitored shortly after emergence. In late May, early June the potato stem borer larva migrates to potato fields. Wilted plants near border rows early in the season are usually infested with the stem borer. Affected plants have a hole at the base of the stem.

Thresholds
Not established.

Management Notes
The potato stem borer is an occasional pest of potatoes. Good weed control, especially of grasses surrounding the field, reduces potato stem borer damage.