What is a Growing Degree Day (GDD)?

A Growing Degree Day is a unit of heat accumulation used to predict plant and pest development. It is calculated as: GDD = ((daily high + daily low) / 2) - base temperature. If the result is negative, GDD = 0 for that day. For grapevines, the standard base temperature is 50 degrees Fahrenheit (10 degrees Celsius).

What base temperature should I use for grapes?

The standard base temperature for grapevine GDD calculations is 50 degrees Fahrenheit (10 degrees Celsius). This is the temperature below which grapevines show minimal growth. Some specific pest models use different base temperatures, so check the relevant pest model documentation.

How are GDD used in vineyard management?

GDD accumulations help predict vine phenology (budbreak, bloom, veraison, harvest ripeness), time spray applications for pest and disease management, schedule canopy management tasks, and estimate harvest dates. Different varieties reach key stages at different GDD thresholds.

What GDD thresholds are important for grape growing?

General thresholds for Vitis vinifera (base 50F): Budbreak occurs around 100-200 GDD, bloom around 500-700 GDD, veraison around 1400-1600 GDD, and harvest ripeness around 2000-2800 GDD depending on variety and wine style. These are regional estimates and can vary.

Growing Degree Day (GDD) Calculator

The Growing Degree Day Calculator tracks heat accumulation to predict grapevine development stages and pest/disease emergence timing. Enter daily high and low temperatures, select your base temperature (commonly 50F for grapes), and the tool computes daily GDD values and cumulative totals. Use GDD accumulations to time spray applications, predict bloom, veraison, and harvest windows.

Temperature Data Entry

Base Temperature (°F)

Standard for grapes: 50°F (10°C)

Date

Daily High (°F)

Daily Low (°F)

Important Safety Disclaimer

This tool is for informational and planning purposes only. Always read and follow the complete product label before any pesticide application. The label is a legal document and takes precedence over any calculator output. Consult a licensed Pest Control Advisor (PCA) for site-specific recommendations. VitiScribe is not responsible for decisions made based on this tool.

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