Blackcurrant Gall Mite Emergence Charts

These emergence charts are designed to help you time your control measures.

Using weather data from the MetOffice (DataPoint) and Met Norway, this tool estimates when blackcurrant gall mites are likely to emerge from big buds for 16 key grower locations and 141 locations overall. This tool is based on research carried out by Prof. Jerry Cross at East Malling from 1995-1999 on the varieties Ben Tirran and Ben Lomond.

How to use

Current season

• By default the dashboard shows data for 27 locations in the key regions. To show data for ~150 locations across the UK, select ‘Current season (all regions)’ from the top left, then click the 'GO' button
• Display the accumulated temperature sum for a particular location in the graph by clicking the coloured dot on the map. Select more locations by holding the ‘Ctrl’ button or using the 'Rectangle select' button on the map
• In the 'Current season (key regions)' view, each line in the graph represents a single location but in the 'Current season (all regions)' view each line in the graph represents the average for all selected locations in that region
• In the 'Current season (all regions)' view locations can be filtered by country and region (England and Scotland only) by selecting from the dropdown list
• You can move the ‘Date range’ slider to compare how much chilling occurred over a particular time interval

Cross-season comparison

• Select ‘Previous seasons (key regions)’ then click the 'GO' button to show a comparison with other years for a subset of locations in the key regions
• You can choose different years from the Years dropdown box
• Clicking on a year in the legend above the graph will highlight the corresponding line in the graph
• Note that each line represents the average for all locations selected on the map. Due to missing data, not every location is necessarily included in every year.
• Hover over the locations on the map and the lines in the graph for more information.

What to do next

• The 100 mark on the graph represents when the first mites will emerge and has shown to be accurate to within three days over the last decade. 
• You are normally advised to apply control treatments just before the line reaches this mark.
• When the line transitions to the blue section, it identifies when 50% of the mites have emerged. Growers have generally aimed to apply their second control treatment just ahead of that time.
• To avoid the possibility of yield losses, applications need to be made by the time the first grape is visible.
• We recommend you are guided on the exact timing and the choice of control products by a BASIS qualified fruit consultant

Blackcurrant Gall Mites

Primarily a pest of blackcurrants, the gall mites are less than 0.25mm long. They feed and breed within buds causing distinctive bud swelling.

Mites emerge from infected buds in the spring and seek new buds. Infested buds start to swell in summer, but are most obvious in winter.

Reversion virus is carried by mites and substantially reduces cropping.