Alfalfa Seed Chalcid

Bruchophagus roddi

Seed chalcid larva

Alfalfa seed chalcid larvae.

ASC damage

Alfalfa seed chalcid damage.

Seed chalcid adult

Alfalfa seed chalcid adult.

Seed chalcids are tiny wasps that develop as larvae inside individual seeds. They are primarily a problem in alfalfa seed production. Overwintered larvae pupate inside seeds around the end of April, and adult wasps fly from the middle of May until the end of June. Damage occurs during June, July and August. Alfalfa pods that are 8-9 days old are most attractive for oviposition. No satisfactory control exists for this tiny insect and insecticide applications are not recommended. Efforts at chemical control are usually ineffective because the extended oviposition period that is longer then the residual activity of products, which also have relatively short pre-harvest intervals. If seed production is planned, volunteer alfalfa should be eliminated along field margins by mowing or herbicide application. If seed can be harvested by mid-August, late season infestation will be minimized. Clean seed to be stored through the winter as uncleaned seed can be a source of calcids if infested.

Page last updated 4/17/2024 by J.P. Michaud.