Sugar beet wireworm (Limonius californicus)
Pacific Coast wireworm (Limonius canus)
Pest description and crop damage Smooth, hard-bodied, cylindrical, shiny tan "worms" about 1 inch long when mature. They have 3 pairs of small, thin legs behind the head; last abdominal segment with characteristic "keyhole" notch. Damage from larval feeding appears as seed destruction during germination. On older plants, wireworms scar and channel the taproot surface as well as chew winding tunnels into the taproot.
Sugar beets following grassy pastures are at highest risk for wireworm infestations, because, like white grubs, wireworms prefer grasses for egg laying and larval feeding, and wireworm larvae require 2 to 4 years for egg-to-adult development. Corn or cereals in rotation with sugar beets also increase the probability of wireworm infestations, especially if reduced tillage in rotational crops leaves high amounts of organic matter and crop residues in the soil.
Scouting and thresholds No formal economic thresholds exist for wireworm insecticide treatment decisions. In problem fields, use wireworm seed treatments for cereal crops grown in rotation with sugar beets. There are no effective "rescue" treatments that can be applied postemergence in sugar beets for wireworms. Use field history and wireworm baiting stations to determine need for at-planting insecticide treatment against wireworms.
Management-chemical control
- 1,3-dichloropropene (Telone II) and 1,3-dichloropropene/chloropicrin (Telone C-17, Telone C-35)-Preplant soil fumigants.
- alpha-cypermethrin (Fastac CS)-at-planting application at 0.025 lb ai/A. Apply in a 3- to 4-inch T-band over the open furrow at planting in a minimum of 3 to 5 gal/Acre. PHI 50 days.
- azadirachtin-Some formulations are OMRI-listed for organic use.
- (Debug Trés) at 0.0375 to 0.1054 lb ai/A
- azadirachtin/pyrethrins (Azera, Azera Pro) at 0.0125 to 0.025 lb ai/A, and up to 0.044 lb ai/A under extremely heavy infestation. Dilution in a minimum of 30 gal water per acre is recommended for conventional equipment. May be applied by air at the rate of 0.0125 to 0.025 lb ai/A in a minimum of 25 gal water. Do not repeat more than every 5 to 7 days. OMRI-listed for organic use.
- clothianidin (NipsIt INSIDE, Lumisure)-Application only by commercial seed treaters; no on-farm seed-treatment application.
- clothianidin/Bacillus firmus I-1582 (Poncho/Votivo) Application only by commercial seed treaters; no on-farm seed-treatment.
- clothianidin/beta-cyfluthrin (Poncho Beta)-Application only by commercial seed treaters; no on-farm seed-treatment application.
- imidacloprid (Agrisolutions Nitro Shield, Agristar Macho 600 ST, Attendant 480 FS, Axcess Insecticide Seed Treatment, Dyna-Shield Imidacloprid 5, Gaucho 480 Flowable, Gaucho 600 Flowable, Senator 600FS, Sharda 5SC, and others)-Application only by commercial seed treaters; no on-farm seed-treatment application.
- terbufos (Counter 20G Lock'n Load, Counter Smartbox 20G) at 0.6 to 1.2 oz ai/1,000 row ft banded at planting. Apply in 5- to 7-inch band over the row and lightly incorporate to 1 inch. One application per year. Do not place granules in direct contact with seed. Do not exceed 2 lb ai/A. PHI 110 days -or- Apply at 0.6 to 1.2 oz ai/1,000 row ft, modified in-furrow, at planting. Apply in furrow, 2 to 3 inches behind seed drop zone, after some soil has covered the seed. One application per year. Do not place granules in direct contact with seed. Do not exceed 2 lb ai/A.
- thiamethoxam (Cruiser 5FS)-Application only by commercial seed treaters; no on-farm seed-treatment application.
- zeta-cypermethrin-
- (Mustang) at planting, 0.05 lb ai/A. Apply in furrow or in a T-Band (band over open furrow) in at least 3 to 5 gal/A water. PHI 50 days. Do not apply more than 0.15 lb ai/A per season (at planting/foliar applications).
- (Mustang Maxx) at planting, 0.025 lb ai/A. Apply in-furrow or make a 3- to 4-inch T-Band at planting in a minimum of 3 to 5 gal per acre. PHI 50 days for tops or roots. Do not apply more than 0.075 lb ai/A per season. REI 12 hr.