Preventing Cranberry Diseases: How To Treat A Sick Cranberry Plant

Cranberries are a quintessentially American fruit that not many people even realize they can grow at home. If you’re one of the lucky few who have cranberries in their garden, odds are you’re very protective of them and their tart, delicious fruits. Keep reading to learn more about common diseases of cranberries and how to treat a sick cranberry plant.

Common Cranberry Diseases

Here are some of the most common diseases of cranberries: Leaf spot – There are several bacterial and fungal issues that can cause leaf spots on cranberries. These include red leaf spot, Proventuria leaf spot, Cladosporium leaf spot, early leaf spot, and Pyrenobotrys leaf spot. These diseases thrive in moisture and can usually be prevented by irrigating during the day when water has time to evaporate and ensuring the soil drains well. If plants are already infested, treat with fungicide. Red shoot disease – Signs of red shoot disease start when early growth becomes spindly and turns red. While it looks strange, red shoot disease isn’t a serious problem and doesn’t have a definitive treatment. Rose bloom – A fungus that causes some new growth to become thick and pink, like a rose. It can usually be prevented by increasing sun and air flow. It can be treated with fungicide. Cottonball – The berries fill with a cottony fungus, and stem tips wither into a shepherd’s crook shape. The disease can be prevented by good drainage and by removing the previous year’s infected fruits. Stem gall/canker – Shoots die back, and growths develop on stems. Bacteria enter through wounds, so the disease can be prevented by avoiding winter and human damage. Sprays containing copper can be effective treatment if the infection isn’t bad. Twig blight – Infected leaves turn dark brown then light tan and stay on the vine all through the winter. Twig blight can be prevented by encouraging good sun and air circulation and treated with fungicide. Fruit rot – Many causes include bitter and blotch rot, early rot, hard rot, scald, and viscid rot. You can prevent this by making sure the vines don’t sit in water for too long. If you use flooding, only do it late in the season. False blossom disease – Transmitted by the blunt-nosed leafhopper, the flowers of the plant grow erect and never form fruit. Apply insecticides if you notice a leafhopper infestation.

Liz Baessler
Senior Editor

The only child of a horticulturist and an English teacher, Liz Baessler was destined to become a gardening editor. She has been with Gardening Know how since 2015, and a Senior Editor since 2020. She holds a BA in English from Brandeis University and an MA in English from the University of Geneva, Switzerland. After years of gardening in containers and community garden plots, she finally has a backyard of her own, which she is systematically filling with vegetables and flowers.