Don’t Leave Lygus Homeless: Build Them a ‘Home’ in Alfalfa

Alfalfa fields are starting to get another fresh cut.

Field scout Damien Jelen reports some alfalfa growers started to harvest their alfalfa field last week and others will follow suit this week. During his scouting rounds, he found an increase in beet armyworms and plenty of lygus bugs. In one alfalfa field, for example, he counted 40 lygus bugs per 50 passes of his sweep net.

Lgyus bugs abound in alfalfa this year.

You might recall UC IPM extension advisor Dr. Pete Goodell indicated early this spring he anticipated a big year for lygus populations because of the wet winter.

With the first squares emerging on cotton plants across the Valley, it’s time for farmers to start worrying about lygus invading their cotton fields. 

Alfalfa is a favorite habit for lygus. It’s time to remind alfalfa growers about the importance of leaving strips of uncut alfalfa in the fields, especially when there is cotton growing nearby. The strips will serve a habitat for lygus to stay in and keep them from fleeing to a cotton field, which is not their preferred home.

An uncut strip of alfalfa provides a habitat for lygus bugs.

Damien says growers seem to be getting that message. “I’ve seen growers leaving the strips out there.”

UC IPM points out that lygus bugs are a threat to cotton from the earliest squaring through final boll set. The pests pierce squares, which can shrivel, turn brown and drop to the ground. Losing too many squares will trigger vegetative growth in the plants and end up reducing yields.

Here are tips from UC IPM about strip cutting alfalfa for lygus management:

• Maintain nearby alfalfa fields in a fresh condition.
• Avoid cutting all alfalfa fields in an area within a short time period. Leave an uncut strip along the border between alfalfa and cotton to slow lygus migration.
• If lygus populations get very high, uncut strips of alfalfa may be treated with an insecticide if needed, but sprays should be avoided where possible to protect beneficial insects.

This practice should be followed for alfalfa fields that are within a two mile radius of a cotton.

 FIELD DAY: Speaking of alfalfa, we are spreading the word about a field day featuring alfalfa pest management tips and an update on pesticide regulatory issues. Sponsored by the San Joaquin Sustainable Farming Project, the free event will be Tuesday, June 20 from 10 a.m. to 12:30 p.m. at Los 3 Pancho Restaurant, 2031 Blossom Street.  Merced County Assistant Agricultural Commissioner Yvette Pellman and Dr. Pete Goodell of UC IPM are the featured speakers. Growers will learn about non-fumigant VOC regulations, chlorphyrifos and worker protection as well as integrating multiple approaches to pest management in alfalfa.  The field day has been approved for continuing education credits. For more information, contact SJSFP Director Marcia Gibbs at (530) 5325 or Marcia@sustainablecotton.org