Phenology is the study of seasonal biological development. The progress of plants and animals can be quantified, based on prevailing weather. Many models of development have been tested for various species of crops and insects. Each gives a mathematical formula that is supposed to be linear with development. These formulas use maximum and minimum daily temperatures as arguments, and most require threshold and cutoff temperatures as parameters to constrain growth outside ideal conditions. All predict growth due to the amount of heat present in the environment to speed development. This is expressed as a product of temperature and time: Growing Degree-Days.

Painting:  Orchard with Flowering Apricot-Trees

Orchard with Flowering Apricot-Trees (1888, van Gogh)

1   Introduction

As cumulative Growing Degree-Days increase throughout the season, milestones in development of each species are passed when biological treatments and controls may be enacted. The needs of the past are observed, and the effort and material required to secure future crops are minimized by applying resources at optimal times.

  • Historical Context

    The study of the development of living things is as old as time. It was fundamental to the need for calendars, which paved the way for the study of writing and mathematics and ultimately brought about the Historical Era.

  • Digital Computing

    In the 1960s, high-speed digital computing became cheaper, and building elaborate mathematical models for the growth of plants and animals became feasible.

  • WeeWX Extension

    This announces an extension to the WeeWX software suite by Tom Keffer and Matthew Wall, which runs on Linux operating systems. The software interoperates with several dozen brands of home and backyard weather stations. This extension module calculates and charts cumulative Growing Degree-Days, according to various published models. Also, it provides a drop-in replacement for the WeeWX Image Generator. The Phenology Image Generator implements transparent chart layers.

  • Control of Codling Moth

    Codling moth (Cydia pomonella) is a major insect pest of apples and other fruits and nuts worldwide. It is the proverbial and the ecological "worm in the apple." The development models for codling moth are advanced. Here is a real-world example, using the Phenology WeeWX Extension to predict when to spray control chemicals.

This document supersedes the one written for the Cydia WeeWX Extension. The Cydia Extension is obsolete. The Phenology WeeWX Extension is written in Python 3 and has been tested with WeeWX 4.2.0 and subsequent versions.

Disclaimer: I am a sales associate for a world-wide discount retailer. I am a systems analyst by training, and I have worked in the field for a regional grocery distributor, a worldwide consumer electronics manufacturer, and a "Big 10" university. Beyond tending a backyard orchard, I have no credentials whatever in the life sciences. The information herein is drawn from sites publicly available on the Internet.