Sugar beet-Sugar beet crown borer

Hulstia undulatella

Pest description and crop damage Caterpillar is a dirty brown color with a green tint. Larvae feed on petioles at the plant crown and along the side of the taproot. They remain by day just below the soil surface within soil-coated silken tubes that extend 2 to 6 inches from infested plants. They are most damaging as first-generation larvae during May.

Management-chemical control

  • terbufos (Counter 20G Lock'n Load, Counter 20G Smartbox)-One application per year. Do not place in direct contact with seed. Do not exceed 2 lb ai/A. PHI 110 days for at planting banded, at planting in-furrow, or postemergence applications.
    • At planting-Apply at 0.6 to 1.2 oz ai/1,000 row ft banded or modified in-furrow. Apply in 5- to 7-inch band over the row and lightly incorporate or apply in furrow 2 to 3 inches behind seed drop zone after some soil has covered the seed. Use 1.2 oz ai/1,000 row ft rate if especially heavy infestations are expected.
    • Postemergence-Apply at 0.6 to 1.2 oz ai/1,000 row ft banded. Apply in 5- to 7-inch band over the row; lightly incorporate. Apply at first sign of infestation.
  • zeta-cypermethrin-
    • (Mustang) at 0.028 to 0.05 lb ai/A. PHI 50 days. Do not apply more than 0.15 lb ai/A per season (at planting/foliar applications). Apply with ground or air equipment using enough water to fully cover foliage.
    • (Mustang Maxx) at 0.014 to 0.025 lb ai/A. PHI 50 days for tops or roots. Do not apply more than 0.075 lb ai/A per season. REI 12 hr. Apply by air or ground using minimum of 2 gal per acre by air and 10 gal per acre by ground.

Note: See University of Idaho publication CIS 845, The Sugar Beet Crown Borer in Idaho, for more details.