Field OPS & Areas
Fruit fly trap installation and maintenance
Before sterile male releases commence
In orchards and vineyards, Yellow Delta traps should be placed at a density of 1 per 25-ha block. This will change after the start of sterile fly releases. In towns, the trap density should be about 1 per 5 to 10 ha, and in natural vegetation around the perimeter of the SIT area, about 1 per 50 to 75 ha.
Clearly number each trap using a permanent marker for data recording purposes. Each trap number must remain permanently associated with the same 25-ha quadrant. The GPS coordinates of all traps should be recorded and entered into the SIT GPS system.
Indicating the different wild fly population levels on maps or GIS systems with different size or colour of dot, e.g. green for zero flies trapped, yellow for 1 to 10 flies/trap/week, red for more than 10 flies/trap/week, is a very useful way of keeping up to date with the changing population densities in different areas of the SIT programme.
Place the lure on the glue in the centre of the trap bottom, and ensure that it is not covered with gum.
Install traps in late winter to establish baseline infestation levels. Where possible place traps in ornamental trees with reasonably dense foliage rather than in fruit trees, as male fruit flies prefer more dense shade. Traps should be as high as practical (± 2 m), and inside the canopy of the tree on the south eastern (cooler) side. Remove any foliage that comes into contact with the trap. Ensure that the trap entrances remain unobstructed throughout the year.
Maintain traps and replace lures strictly according to the manufacturer’s specifications.
Lures and trap bottoms must always be effective, or incorrect decisions will be made. Trap bottoms should be replaced sooner than specified if it is evident that the glue is starting to get depleted, or when it is obvious that its efficacy in trapping fruit flies is decreasing, for example when there is excessive dust or debris in the glue. Replace the whole trap if it becomes misshapen or damaged.
If any trap records zero catches for more than a couple of weeks while other traps nearby are trapping fruit flies, move this trap 100 to 200 m away in the same 25-ha block every 4 to 6 weeks. Record any new trap positions on the GIS system and on the aerial photos in the operations centre.
Trap rotation may be necessary avoid a trap staying in one locality in a 25-ha block with an unusually low fruit fly population, which could give a false impression of the block’s population density.