Monitoring for damaged fruit and larvae

It is important to monitor for damaged and infested fruit both pre and post-harvest. Detecting a problem before picking can save the labour required to pick infested fruit, allowing control measures to be applied before the next pick. Detecting a problem after picking can save on packing costs and prevent damaged/infested fruit reaching the market.


Sampling fruit pre-picking

  • Sample weekly from all plantations at risk.

  • Select more than 100 ripe fruits from a transect across the crop.

  • Include fruits from the edges of plantation near wild hosts.

  • Collect fruits from the lower centres of plants and avoid fruit on the ground.


Sampling fruit post-picking

  • Decide upon the punnet sampling frequency (eg. 1/100).

  • Take a sample from each crop at each picking time.

  • Record numbers: lot size, sample size, number where pest detected.

  • Work out incidence and confidence intervals.

  • Reject the consignment if SWD larvae are found.


How to inspect fruit

Whether sampling pre-picking or post-picking, the fruit should be inspected for signs of infestation on the surface and inside the fruits. Several techniques to assess if fruits contain larvae have been assessed in the UK industry funded research project (SF 145). Results demonstrate that sugar floatation is the most sensitive and rapid test for growers to use.

  • Make up a sugar solution (170 g sugar per litre of water – 15 oBrix)

  • Gently crush the sample of fruit in a clear plastic bag and add the sugar solution to the fruit.

  • Stir the fruit, let it settle for 10 minutes, stir again, and assess 10 minutes later.

  • Any living larvae will float out of the fruit.


Our video explains how to do a floatation test:









You can also download our poster which explains the steps needed to do a floatation test;



























Emergence Test

An emergence test should be undertaken alongside a floatation test. Our video explains how to run an emergence test;