Florida Blueberry Growers Urged to Mind Gall Midge Threat

Florida Blueberry Growers Urged to Mind Gall Midge Threat

Deformed blueberry leaf from gall midge

Deformed leaves are one sign of damage and the presence of midges in the field.
Photo courtesy of UF/IFAS

The Florida Blueberry Growers Association (FBGA) has sent an important message to its members reminding them it’s time to keep an eye peeled for a mighty pest – the gall midge. According to the memo, UF/IFAS researchers have been conducting a limited amount of monitoring for adult gall midge on several farms throughout the state and have made positive identifications.

The FBGA reports gall midge adults were found through the past week in traps in the following regions:

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  • North-Central Florida: 19 adults over two farms
  • Central Florida: 23 adults over five farms
  • South-Central Florida: 0 adults over two farms

Last season, blueberry growers in the Sunshine State suffered widespread damage from gall midge pressure.

Doug Phillips, UF/IFAS Blueberry Extension Coordinator, and UF/IFAS Professor Oscar E. Liburd provided the following specs on gall midge:

Adults are typically active beginning in November, with a peak in January and February in Central and South-Central Florida, and a peak in February and March in North-Central Florida. Emergence is typically triggered by cool days followed by warm days. It is thought that adult males may emerge approximately two weeks before the emergence of adult females.

Monitoring can be done using either a bucket trap placed on the ground below the plant canopy (three to five per acre) or a clear sticky panel trap hung in the lower part of the plant canopy (one to three per acre). At a minimum, monitoring for larvae should be done by placing young stems with buds into a zip-lock type plastic bag at room temperature. If present, young whitish larvae will emerge in three to four days. These larvae will mature and turn orange after six to seven days.

Example of a bucket trap for blueberry gall midge.

Example of a bucket trap for blueberry gall midge. Photo by Elena Rhodes

Spraying with recommended insecticides should begin when two or more adults are found in a trap. During bloom when pollinators are present, the reduced-risk pesticide Delegate (spinetoram, Corteva Agriscience) is used for gall midge management. Once Delegate has dried for three hours it has limited effects on bees. Delegate will kill adult midges if it comes into contact with the adults; however, the pesticide has a relatively short residual activity and will need to be re-applied weekly within label guidelines. Furthermore, because adults live for such a short time (two to three days), the chances of this pesticide being effective against midge is greatly reduced.