This metric defines the minimum period a vector, such as an aphid or leafhopper, must feed to ingest enough of a virus to become infectious. Plant pathologists use it to understand transmission dynamics and time pesticide applications. If an insect is killed before this threshold is reached, the disease cannot spread to healthy crops.
Heard on the job
The new systemic knocks down the aphids well before the acquisition feeding time, so we shouldn't see the virus spread.