I recently visited a field that had quite a bit of rice seed midge injury. In this case, the seedlings that were not injured were almost at the one leaf stage, and one could observe quite a few seeds still in the soil surface. Close inspection of these seeds showed that they had been hollowed out by rice seed midge. Some midge casings were observed as well. Later, I got some reports of more fields injured by rice seed midge in the Colusa area.

Seed injured by rice seed midge

Rice seed midge casings and injured seed

Rice seed midge has been considered a pest of rice for many years. However, it has been an infrequent pest. The thought was that pyrethroid insecticides controlled it. Nevertheless, in the past three years, I have seen considerable injury in fields that had been treated with a pyrethroid.

Ian Grettenberger, UC Davis Entomology Specialist, collected some midges from the field I mentioned above and exposed them to a full rate of a pyrethroid or an insect growth regulator for 48 hours. The larvae survived. We are not sure if the survival is due to low susceptibility or resistance build-up to the pesticides. Ian started doing some pesticide work last year but the results were not clear cut. More work is going to be necessary to improve on the management of this pest. Let us know if you have seen issues with seed midge recently so we can have a better idea of the current importance of this insect.