Converting insect counts

Averaging

Pest populations can be patchy, so when monitoring, insect numbers are recorded at multiple sites within a field to get an accurate representation of the overall population.  The average of these counts is then compared to the relevant threshold for that pest.

For example: If monitoring took place at 12 sites, counts for each species are totalled, then divided by 12.

Adjusting for row spacing

Most thresholds are expressed as pest per square metre (pest/m²). Insect counts in crops with row spacing less than 1 metre must be converted to pests/m² to allow a direct comparison with the threshold. Divide the average insect count per metre of row by the row spacing in metres.

For example: The crop has an average of insect pests per metre of row. Row spacing is 0.75 metres.
2 / 0.75 = 2.67  insect pests per square metre.

Converting species

Some thresholds apply to more than one species if the type of damage is similar, but may have to be adjusted for species if the amount of damage is different. An example of this is the pod-sucking bug threshold in pulses, which converts other podsucking bug species into green vegetable bug ‘equivalents’. For more information, see the Podsucking bugs section on the Beatsheet’s economic threshold calculators page.

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