Pest description and crop damage Widespread in Idaho and the adjoining Oregon production region, they annually reach economically damaging levels. Spring-emerging adult flies lay eggs in soil next to young sugar beet plants during May and June. Soil-borne larvae subsequently feed on the taproot through mid-July, then diapause as non-feeding, overwintering larvae.
Scouting and thresholds
For larval control
- Use field history to determine the need for at-planting insecticides.
- Determine the timing of postemergence insecticide applications by monitoring local flight activity of adult root maggots with orange-colored sticky traps. Control is most effective when insecticide application coincides with the time of peak seasonal fly capture on traps; earlier and especially later application is less effective. Total seasonal captures of 40 to 50 flies per trap through peak collection justify postemergence treatments. See University of Idaho publication BUL 942, Sugar Beet Root Maggot: Identification, Biology, and Management, https://www.extension.uidaho.edu/publishing/pdf/BUL/BUL942.pdf
For adult control
Adult root maggot flies are highly mobile; they continually colonize fields over long distances during a 6-week egg-laying period. Control requires repeated insecticide applications to kill flies before they lay eggs, but this has the potential negative side effects of selecting for pesticide resistant strains and triggering outbreaks of aphid and leaf-feeding caterpillars by eliminating their natural enemies.
- aldicarb (AgLogic 15G, AgLogic 15GG) at 1.05 to 2.1 lb ai/A. PHI 90 days, 120 days if tops are fed to livestock. Do not use tops as food for humans. Do not make more than one at-planting and two postemergence applications per crop. Do not exceed a total of 4.95 lb ai/A per season. Immediately deep-disk any spills at row ends or elsewhere to ensure the granules are covered with a layer of soil. Washington only.
- At planting (or within 1 week prior)-Drill granules 1 to 3 inches below seedline. Granules can be placed into the seed furrow if rate does not exceed 1.05 lb ai/A.
- Postemergence-Apply granules to both sides of plant row and immediately work into the soil or cover with soil, or, for furrow irrigation side-dress granules 4 to 8 inches to water-furrow side of plant row and at furrow depth. Irrigate soon after application. Apply within 60 days after planting. Do not make any postemergence applications if 4.05 to 4.95 lb ai/A was applied at planting or within 1 week prior to planting.
- alpha-cypermethrin (Fastac CS)-at-planting application at 0.025 lb ai/A. For light to moderate infestations; suppression only. Apply in a 3- to 4-inch T-band at planting in a minimum of 3 to 5 gal/Acre. PHI 50 days.
- 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.
- phorate (Thimet 20-G EZ Load, Thimet 20-G Lock'N Load, Thimet 20-G Smartbox)-
- At planting-Apply at 0.68 to 0.9 oz ai/1,000 row ft. PHI 30 days. Do not feed tops or silage to dairy cattle. Do not place granules in direct contact with seed. Drill to side of seed or band over seed. No more than one application per cropping season.
- Postemergence-Apply at 0.98 to 1.5 lb ai/A to foliage when plants are dry. Only one treatment postemergence per season. Do not feed tops or silage to dairy cattle. No more than one application per cropping season.
- spirotetramat (Movento and Movento HL) at 0.07 to 0.14 lb ai/A. PHI 28 days. Do not exceed 0.28 lb ai/A per crop season.
- spirotetramat/pyriproxyfen (Senstar) at 0.07 to 0.141 lb ai/A spirotetramat and 0.025 to 0.049 lb ai/A pyriproxyfen. Suppression only. Thorough coverage is critical. Only whole fields should be treated. PHI 28 days.
- 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.
- 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 incorporate or apply in furrow, 2 to 3 inches behind seed drop zone after some soil has covered the seed.
- 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 fly emergence.
- thiamethoxam (Cruiser 5FS)-Application only by commercial seed treaters; no on-farm seed-treatment application.
- (Mustang) at-planting application for suppression only of light to moderate infestations at 0.05 lb ai/A. Apply in furrow or in a 3- to 4-inch T-Band (band over open furrow) in a minimum of 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. Suppression only. For light to moderate infestations only. Make a 3- to 4-inch T-Band at planting in a minimum of 3 to 5 gal per acre. 50-day PHI for tops or roots. Do not apply more than 0.075 lb ai/A per season. REI 12 hr.
Adult (fly) control
- alpha-cypermethrin (Fastac CS) at 0.014 to 0.025 lb ai/A. PHI 50 days. REI 12 hr. Apply by air or ground equipment using sufficient water to obtain full coverage of foliage (minimum of 2 gal per acre by air and 10 gal per acre by ground). Apply no more than 0.075 lb ai/A per season. Do not graze or harvest treated sugar beet tops for livestock feed.
- esfenvalerate (Asana XL and S-fenvaloStar, Zyrate) at 0.03 to 0.05 lb ai/A. PHI 21 days. Do not apply more than 0.15 lb ai/A per season. Apply with ground or air equipment using enough water (at least 2 gal/A) for uniform coverage.
- naled (Dibrom 8 Emulsive) at 0.94 lb ai/A. PHI 2 days. REI 48 hr. Recommendation as permitted under FIFRA Section 2(ee). Do not apply more than 4.7 lb ai/A per season.
- (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.