Time to Monitor for Blueberry Gall Midge

UF/IFAS has been conducting a limited amount of monitoring for adult gall midge on a few farms throughout the state. This update includes only the north-central region, since the cultivars at all of the monitoring sites in central and south-central regions were already at least at stage 4 of bloom.

This will be the last monitoring update for this season since many of the cultivars in the north-central region monitoring sites are at least at stage 4 of bloom. Gall midge adults were found in traps last week in the following regions:

North-central Florida – 954 adults over 4 farms

Per Oscar Liburd, once a cultivar is at least at stage 4 of bloom (individual flowers distinguishable) there is no need to continue to spray that cultivar for gall midge control.

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. Monitoring can be done using either a bucket trap placed on the ground below the plant canopy (3-5 per acre) or a clear sticky panel trap hung in the lower part of the plant canopy (1-3 per acre) (see Oscar Liburd gall midge bulletin attached). 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 3-4 days. These larvae will mature and turn orange after 6-7 days. 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) is used for gall midge management. Once Delegate® has dried for 3 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. Furthermore, because adults live for such a short time (2 to 3 days) the chances of this pesticide being effective against midge is greatly reduced.

Doug Phillips
UF/IFAS Blueberry Extension Coordinator

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