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

Alfalfa seed-Spider mite

  • Facebook logo

Includes

Pacific spider mite (Tetranychus pacificus)
Strawberry spider mite (T. turkesani)
Twospotted spider mite (T. urticae)

Pest description and crop damage Not insects, mites are eight-legged animals less than 0.03 inch long. Mites pierce the epidermis of the leaf's underside and suck juices, causing yellowing, bronzing, and even leaf death. Canopies of silk covering plants accompany large populations of twospotted mite, and serious plant injury and yield loss result. (Chemical controls should be applied much earlier to prevent this damage.)

Sampling and thresholds Late-season infestations may not affect seed production seriously (after seed has been set and harvest is less than 2 weeks away). Treatment may be justified when 25% of leaves show damage in early summer, 50% in midsummer. Treatment actually may not be justified with 75 to 100% leaf damage after August 15, as seed usually has been set and fields are drying before harvest.

Management-chemical control

  • abamectin (Agri-Mek, AbbA Ultra) at 0.01 to 0.02 lb ai/A via ground application; 0.014 to 0.02 lb ai/A via air application. PHI 12 hr. Do not retreat within 21 days. Do not exceed two applications or 0.04 lb ai/A per season. No part of crop may be used as feed. Do not apply at ground level within 25 ft of aquatic habitat, 150 ft if applied by air.
  • azadirachtin + pyrethrins (Azera) at 0.01 to 0.05 lb ai/A. Apply in early morning or late evening hours to avoid harming honey bees. It can be used up to and including the day of harvest. Do not apply more than 1 time per day and more than 10 times per season. Do not reapply within 3 days except under extreme pest pressure. ID EPA Reg. No. 1021-1872.
  • Beauveria bassiana strain GHA (BotaniGard WP) at 0.11 to 0.44 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.
  • bifenazate (Acramite 4 SC, Vigilant 4 SC) at 0.5 to 0.75 lb ai/A. PHI 14 days. REI 12 hr. Make only one application per year. SLN OR- 080031; WA 070008; ID-070006; NV-070003; UT-070003; WY-070004.
  • bifenthrin (Sniper) at 0.06 to 0.1 lb ai/A. REI 12 h. Apply in a mimimum of 5 gal water per acre by air equipment or in a minimum of 20 gal water by ground equipment. When applying by air, 1 to 2 qt emulsified oil may be substituted for 1 to 2 qt water in the finished spray. Do not apply by ground equipment within 500 feet, or by air within 0.25 miles, of water bodies containing fish or aquatic invertebrates, including lakes, reservoirs, rivers, permanent streams, marshes, or natural ponds, estuaries, and commercial fish farm ponds. Maintain a minimum of 21 days between applications. Rotational crops may be planted no sooner than 30 days after last application.
  • hexythiazox (Onager) at 0.09 to 0.13 lb ai/A. PHI 28 days. REI 12 hr. One application per season. Do not graze or cut crop for hay or forage. Effective on immature motile mite stages.
  • Isaria fumosorosea Apopka strain 97 (ANCORA) at 14 to 28 oz ai/100 gal water. Repeat applications at 3 to 10 day intervals over 2 to 3 weeks or as needed to maintain control. Formerly Paecilomyces fumosoroseus. More frequent application at low rates (e.g., 14 to 16 oz/100 gal every 3 to 5 days) is more likely to improve results than using higher rates at low frequency (e.g., 28 oz/100 gal every 10 days). ID EPA Reg. No. 70051-19-59807.
  • 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.
  • mineral oil (Damoil, 440 Superior Spray Oil) at 0.25 gal (1 qt) of this product per acre in a minimum of 10 to 30 gal water per acre by ground application or minimum of 10 gal per acre by air. REI 12 hr.
  • sulfur (Sulfur DF) at 2.4 to 4 lb ai/A. PHI 0 days. REI 24 hr. Repeat every 14 days as necessary.