More on Downy Mildew Diseases

Jan 31, 2019

By Steven A. Tjosvold

Now through the spring is the time to take a close look at crops that are susceptible to downy mildew so that the disease can be detected early. This post follows the previous one that describes the general identification and biology of downy mildew diseases. Here are some more images illustrating the symptoms on various ornamental crops.

Downy mildew on impatiens caused by Plasmopara obducens affects all Impatiens walleriana hybrids, but does not affect New Guinea impatiens. (LEFT) Symptoms of impatiens downy mildew often first occur on leaves near the tips of branches. At first, the top of leaves can develop an irregular yellow-green or purple discoloration. Affected leaves often curl downwards. Infected plants are often stunted. Leaves and flowers can eventually drop off, leaving a bare stem. The pathogen in wet and cool

Downy mildew on impatiens can lead to severe defoliation and death

conditions can sporulate profusely producing a fuzzy white mass on the under sides of leaves, stems and flower buds.

Possibly the first indication of downy mildew on impatiens

Downy mildew sporulation on undersides of leaves and buds (circled)

Downy mildew on impatiens can lead to severe defoliation and death

Downy mildew on statice grown for cut flowers in field

Downy mildew on statice

Sporulation of downy mildew on statice

Downy mildew on delphinium (Delphinium species and cultivars) caused by Peronospora ficariae. (BELOW) Initial symptoms on leaves consist of light green patches. These areas quickly turn dark green to blackish green and often delimited by the central vein of the leaf. Purple-gray sporulation of the pathogen seen primarily on the underside of leaves. Symptoms are most severe on older foliage. As disease progresses, the lower leaves wither and dry up, giving the plant a blighted appearance.

Downy mildew on Delphinium

Downy mildew on hebe (Hebe species) caused by Peronospora grisea. (BELOW). The disease is usually noticed first by a yellowish discoloration often with purple halos on the lower leaves of the plants. Leaves become curled and distorted. A grayish- brown sporulation may develop on the underside of the leaves. Eventually the affected parts of leaves turn brown and shrivel. Plants can be entirely defoliated and killed.

Downy mildew of Hebe

Sporulation of downy mildew on Hebe

Downy mildew on snapdragon (Antirrhinum majus) caused by Peronospora antirrhini. (BELOW) Young tip leaves are dull green, severely stunted, and roll downward. Gray-purple fungus grows on undersides of leaves. Disease is common on seedling phase; large plants are less frequently attacked. Infected plants fail to produce flowers.

Apparently healthy flat of snapdragon seedlings, except......

Downy mildew on snapdragon, closeup

Source:ucanr.edu

Video: Why Port Infrastructure is Key to Growing Canada's Farms and Economy

Grain Farmers of Ontario (GFO) knows that strong, modern port infrastructure is vital to the success of Canada’s agriculture. When our ports grow, Ontario grain farmers and Canadian farms grow too—and when we grow, Canada grows.

In this video, we highlight the importance of investing in port infrastructure and how these investments are key to growing Ontario agriculture and supporting global trade. The footage showcases the strength of both Ontario’s farming landscapes and vital port operations, including some key visuals from HOPA Ports, which we are grateful to use in this project.

Ontario’s grain farmers rely on efficient, sustainable ports and seaway systems to move grain to markets around the world. Port investments are crucial to increasing market access, driving economic growth, and ensuring food security for all Canadians.

Why Port Infrastructure Matters:

Investing in Ports = Investing in Farms: Modernized ports support the export of Canadian grain, driving growth in agriculture.

Sustainable Growth: Learn how stronger ports reduce environmental impact while boosting economic stability.

Global Trade Opportunities: Improved port and seaway systems help farmers access new global markets for their grain.

Stronger Communities: Investment in ports means more stable jobs and economic growth for rural communities across Ontario and Canada.

We are proud to support the ongoing investment in port infrastructure and to shine a light on its vital role in feeding the world and securing a prosperous future for Canadian agriculture.

Special thanks to HOPA Ports for providing some of the stunning port footage featured in this video.