Detecting Cranberry Growth Stages Using Computer Vision Systems

Ariana Negreiro, Dharani Suresh Babu, John Daniels

Motivation

Growing cranberries requires regular inspection of the plants to ensure that there is nothing impeding their growth development. Our project aims to train a deep convolutional network to automatically detect and classify images of cranberries by growth stage, and allow for rapid, automated identification on new images. Challenges in accurately identifying growth stage include lighting conditions and detecting individual plants within the dense groups of cranberries captured in each image, in addition to correctly discriminating between stages. Since the initial project proposal, our scope has increased to include training a second model to compare to our originally planned model, to examine the relative advantages to each approach.


This review required heaps of understanding of cranberry crop physiology, image processing and computer vision techniques. The main challenge with this study is that cranberries are a perennial crop and morphologically look very small. Calculating developmental stages should consider the carryover effect from the previous year since it's a perennial crop.

Bud stage

Hook stage

Blossom stage

Cranberry Growth Cycle

Cranberry Growth Cycle

Cranberry is a perennial crop and it has a 16-month life cycle – that’s more than one year! Cranberries do not grow in water. They grow on vines in beds that have sand, peat, gravel and clay. The beds are called bogs. The bogs are flooded with water when it’s time to harvest them.Cranberry terminal buds are initiated in the year. The trigger for this process is changing daylength. The buds continue to develop throughout the rest of the summer and fall, with floral buds being formed within the terminal bud. The initial stages of the flower bud can be found and visible changes in the buds continue. Bud development almost certainly continues later into the year in milder growing areas. Eventually the flower buds become dormant until the following spring. The signal to enter dormancy is most likely a combination of low temperatures and short days. The dormant state lasts until the plant has been exposed to sufficient ‘chilling hours’- hours of temperatures between 32ºF and 45ºF to complete the dormant cycle.

For our project work, we are considering 9 important growth stages among 16 stages since these are the 9 stages, farmers find it important for optimizing their management practices and to have more fruit yield. Those 9 stages are dormancy, bud tight, bud break, roughneck, hook, blossom, blush, sizing and mature fruit.

Approach

Our project focused on two different Convolutional Neural Network (CNN) architectures: ResNet and YOLO. The ResNet model was included after experiencing how time-consuming manual annotation of the cranberry training images was. Our intent was to compare the accuracy of YOLO, which requires annotation of images to mark objects with a bounding box, to that of ResNet, which can be trained with whole unannotated images. These two models were chosen as they are top-of-the-line models known for speed and accuracy in object detection.

YOLOv3 Model

ResNet Model