1. Insect
  2. Legume, Grass, and Field Seed Crops
  3. Pests of Alfalfa Grown for Seed

Alfalfa seed-Aphid

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Includes

Alfalfa aphid (Macrosiphum creelii)
Blue alfalfa aphid (Acyrthosiphon kondoi)
Pea aphid (Acyrthosiphon pisum)
Spotted alfalfa aphid (Therioaphis maculata)

Pest description and crop damage Pea and alfalfa aphids are the common light-green aphids found on stems in the upper canopy. Aphids feed on plant sap. Large numbers can stress and yellow alfalfa. Blue alfalfa aphid causes less damage than pea aphid. Spotted alfalfa aphid is small and yellow to brown with red bumps on its back. It secretes much honeydew and injects toxins that injure some varieties. It is a hot weather aphid population that typically increases as other aphids decline and is very difficult to control. Spray at ground with at least 25 gal/A water. Damage is most severe on seedling stands.

Sampling and thresholds Control the pea aphid in alfalfa grown for seed if populations approach 100 per sweep, the plants are less than 1 foot high, the field is under water stress, and aphid populations show no sign of leveling off. If blue alfalfa aphid has been confirmed in the area and fields have been damaged, treat when numbers reach 30 per sweep. Begin scouting for spotted alfalfa aphid in late June or early July. In established stands, treat when spotted aphids average 20 to 30 per stem, or 50 per sweep, and the population is increasing.

Management-chemical control

  • Beauveria bassiana strain GHA (BotaniGard WP) at 0.11 to 0.22 lb ai/A in 100 gal. PHI 0 days. This product is potentially pathogenic to honeybees. Avoid applying to areas where honeybees are actively foraging or around beehives. Drift and runoff may be hazardous to aquatic organisms in water adjacent to treated areas. Typically, it takes 7 to 10 days after the first spray to see control. Apply at 5- to 10-day intervals for low to normal pest pressure. For high pest pressure, especially aphids, apply at 2- to 5-day intervals. Repeat applications for as long as pest pressure persists. There is no limit on the number of applications or total amount of product that can be applied in one season.
  • chlorpyrifos (Chlorpyrifos 4E-AG) at 0.5 to 1 lb ai/A. REI 24 hr. Application rates will vary depending on the nozzle droplet type. Toxic to fish, aquatic invertebrates, small mammals and birds. Highly toxic to bees. Buffer zones must be utilized for aquatic areas when using ground boom (25 ft), chemigation (25 ft), orchard airblast (50 ft), and aerial (150 ft). Do not cut or graze alfalfa within 7 days after application of 0.5 pint/A, 14 days after application of 1 pint, and 21 days after application of > 1 pint/A. Labeled for Idaho.
  • dimethoate (400EC, Dimate 4E) at 0.25 to 0.5 lb ai/A. PHI 10 days. REI 48 hr. For suppression only. Do not apply if crop or weeds are in bloom. Effective only on cutting to which chemical is applied. Do not feed or graze livestock. Do not apply more than once per cutting cycle and more than three times per year. Minimum retreatment intervals of 30 days.
  • flonicamid (Beleaf) at 0.089 lb ai/A. REI 0 hr. Do not apply more than twice a season. Apply in a minimum of 3 gpa by air or 10 gpa by ground. This is the preferred insecticide during the bloom period due to safety for pollinators.
  • gamma-cyhalothrin (Proaxis, Declare) at 0.01 to 0.015 lb ai/A. PHI 1 day for forage, 7 days for hay. REI 24 hr. Do not exceed 0.06 lb ai/A per season or 0.015 lb ai/A per cutting. Do not apply on ground within 25 ft of aquatic habitat, 150 ft if applied by air, or 450 ft if applied from ULV.
  • lambda-cyhalothrin + chlorantraniliprole (Besiege) at 0.03 to 0.06 lb ai/A. PHI 1 day for forage and 7 days for hay. Do not exceed a total of 31.0 fl oz per year. Do not apply more than 10.0 fl oz per acre per cutting and no more than 1 application per cutting. Avoid application when bees are actively foraging by applying during the early morning or during the evening hours. It may be advisable to remove bee shelters during and for 2-3 days following application. Avoid direct application to bee shelters.
  • lambda-cyhalothrin (Serpent 1EC, Warrior II) at 0.02 to 0.03 lb ai/A. PHI 1 day for forage, 7 days for hay. REI 24 hr. Do not apply more than 0.03 lb ai (3.84 fl. oz or 0.24 pint of product) per acre per cutting, or more than 0.12 lb ai (15.36 fl oz or 0.96 pint of product) per acre per season. Do not apply on ground within 25 ft of aquatic habitat (groundboom, overhead chemigation, or airblast), 150 ft if applied by air, or 450 ft if applied from ULV. Do not apply while bees are active. Advisable to move bee shelters for 2 to 3 days after application. Avoid application when bees are actively foraging by applying during the early morning or during the evening hours.
  • malathion 8EC at 0.75 to 1 lb ai/A. PHI 0 days. REI 12 hr. Not effective below 65ºF. WA only.
  • permethrin at 0.05 to 0.2 lb ai/A. PHI 0 days at rates equal to or less than 0.1 lb ai/A, 30 days at rates greater than 0.1 lb ai/A. REI 12 hr. Do not reapply at less than 7-day intervals or exceed 0.2 lb ai/A per cutting. If used during bloom, remove bees from field for 3 days. Do not apply on ground within 25 ft of aquatic habitat, 100 ft if applied by air, or 450 ft if applied from ULV.
  • pymetrozine (Fulfill) at 0.086 lb ai/A when aphids first appear. PHI 14 days. Do not exceed 0.086 lb ai/A per cutting or 0.17 lb ai/A per season. Can be toxic to bees. SLN ID000010; WA000016; OR040005.
  • sulfoxaflor (Transform WG) at 0.023 to 0.031 lb ai/A. PHI 7 days for harvest. Do not make applications less than 7 days apart. Do not make more than 2 applications per season. Follow all pollinator safety guidelines for applications made during bloom.
  • zeta-cypermethrin (Mustang Max) at 0.014 to 0.025 lb ai/A. PHI 3 days for cutting or grazing, 7 days for harvest. REI 12 hr. Allow at least 7 days between applications. Do not exceed 0.05 lb ai/A per cutting or 0.15 lb ai/A per year. Do not apply on ground within 25 ft of aquatic habitat, 150 ft if applied by air, or 450 ft if applied from ULV.