Vector pressure index

Each week the scheme participant recieves the results from their trap with a cumulative vector pressure index. This index is designed to give the user an assessment of the risk to their crop of PVY spread.

It is calculated as follows:

  1. For each species multiply the number in the trap by the relative transmission efficiency* value
  2. Add the results together for all species caught in the trap
  3. Add this value to the previous weeks cumulative vector pressure index
*The relative transmission efficiency is a measure of how often an aphid species will transmit the virus relative to the 'best' vector, Myzus persicae. M.persicae is given a value of 1.0 and the values for the other species are proportional to this. For example, Aphis fabae has a relative transmission efficiency of 0.1, meaning that in the same conditions, this species transmits the virus only 10% of the time compared to M.persicae.