Carrot Weevils

(photo coming)

Family name: Apiaceae

Latin name: Listronotus oregonensis

Description: The larvae of carrot weevils cause significant damage to carrot family crops, most notably carrots, celery, and parsley. The adults are 1/6” long, having dark brown bodies and large snouts. Even though they have functional wings, they mostly walk. The larvae are cream-colored with brown heads and eggs are initially white but become dark prior to hatching. It is interesting to note the adult weevils are more attracted to organic soil and avoid sandy soil.

Life cycle: Mated adults overwinter in the soil, emerge in the spring, and begin feeding on plant foliage. They lay 2 to 4 eggs in the petioles (where a leaf attaches to a stalk) of seedlings or on the crowns of the plants at the soil level. Females seal the egg cavities with a dark secretion; gardeners should watch for this as an indicator of their presence. The eggs hatch in 7 to 14 days and the larvae tunnel down into the roots while going through 4 instars. They often move from the root of one plant to another. After tunneling down to the root hairs, they pupate for 5 to 10 days. There are two generations in a year.

Typically seen on: Carrot family crops (carrots, celeriac, celery, dill, fennel, parsley, and parsnips).

Signs of their activity: Scars on leaf petioles or plant crowns; yellow leaves; wilting leaves; dead plants.

Controls:

  • Hand-pick adult weevils
  • Trap adults before the seeds germinate by sinking a container into the soil so the top of the container is at soil level; fill the trap with soapy water which will coat the bodies of any adults that fall in
  • Use a 3-year crop rotation for all members of the carrot family
  • Plant carrot family crops later to avoid egg-laying season w Cover plantings immediately with row covers to keep weevils away
  • Clean up all plant debris and weeds near the garden to remove overwintering locations
  • Note that sprays are generally ineffective because the larvae are relatively protected within the plant roots or soil
  • Disturb top layer of soil to expose overwintering weevils to predators and winter temperatures

Natural predators: Ground beetles, parasitic wasps, and beneficial nematodes (Steinernema carpocapsae, S. riobrave, S. feltiae, Heterorhabditis bacteriophora).

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