> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agrihub360.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Pest Forecasts
> Degree-day risk windows, specific to UK crops.
## What It Tells You
A **pest forecast** says when the weather has favoured a pest or a disease on a field, before symptoms show. Aphids develop with temperature, so the [BYDV](/models/bydv) count runs on degree-days. Septoria, yellow rust and brown rust need hours of leaf wetness inside each pathogen's temperature range. The [Foliar Disease Risk](/models/foliar-disease) model gives each wheat field a pressure level per disease during the latent period, when nothing is visible. Fusarium head blight infects at flowering. The [Fusarium Head Blight Risk](/models/fusarium-head-blight) model gives a probability for the week around anthesis. A forecast describes conditions. It says infection was favoured. It does not say the crop has the disease.
## How It Works
Each forecast runs a degree-day or published risk model. BYDV sums degree-days above 3 °C from emergence. Foliar disease accumulates wet hours at infective temperatures from a leaf-wetness sensor on the field, scaled by the variety's susceptibility rating. FHB reproduces a published logistic regression on hours of warmth, humidity and rain around anthesis. Each model writes a row per field per day. The field card shows the result, or the reason when the model cannot answer.
