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 Plant Disease

Good gardening practices


Good gardening practices will prevent many plant diseases and deficiencies before they begin.


Ensure your soil is healthy by enriching it with homemade compost and other appropriate nutrients. This builds strong plants which are more resistant to many plant diseases.


Avoid planting the same crops in the same location year after year. This is especially important in vegetable gardens.


Keep your garden clean and tidy. Infestations or disease may start on nearby weeds or dead foliage and then migrate to your healthy plants.


Feed and water your plants regularly as directed (most annuals need weekly fertilizing). Properly nourished plants stay vigorous and are less susceptible to infestation and disease.


Although there are numerous diseases that can attack your plants, home gardeners are likely to only experience a few of the more common ones. Click on any of the following to determine if this disease is your problem.


Botrytis blight

• Common to tulips, it's caused by a fungus.
• Light to dark colored spots appear on part or all leaves and flowers.
• In cool, moist weather a fuzzy brown or grayish mold forms; leaves and stems distort, and often rot off at the base.
• Bulbs have dark, circular, sunken lesions; and dark brown pinhead sized pellets form on the bulb husks.


Botrytis blight


Remove diseased plants. Using a spreader sticker, treat emerging plants when they are 4 inches tall, spray them with a fungicide containing benomyl.


Spray plants every 5 to 7 days until the flowers bloom. Move plants to new location next year.



Crown rots

• Most severe when overcrowded, above 70F and moist conditions.
• Leaves irises grown from rhizomes die, leaf tips form downward.
• The leaf bases and possibly the rhizomes are dry brown, and rotted.
• Leaves, stems at soil level are rotted, bulbs are soft and crumbly.


Crown rots


Remove and destroy infected plants, and soil 6 inches around plant. Drench area with a fungicide containing PCNB. Next year redrench soil at planting time and again when new growth is showing.


Plant in well drained soil with roots covered and tops of rhizomes showing at the soil line. Thin out overcrowded plantings.



Leaf spots

• Several disease and environmental factors contribute to spotting and blotching of leaves. Fungal and bacterial leaf spots are most common.
• Fungal leaf spots are 1/4 inch yellow, red, tan, gray, brown, or black circular spots on leaves.
• Bacterial leaf spots are usually tiny, angular dark colored and may be accompanied by rotting and oozing.


Fungal leaf spots

Remedy - Fungal leaf spots

Picking off diseased leaves gives adequate control. If severe, spray with a fungicide containing chlorothalonil, mancozeb, or zineb. Make sure your plant is listed on the fungicide label.


Bacterial leaf spots

Remedy - Bacterial leaf spots

Pick off spotted leaves or discard plant if severe. Avoid overhead watering. Dip contaminated tools in rubbing alcohol.




Powdery and downy mildews

• Flour like patches on surface of leaves, buds, young stems, fruits.
• They thrive in both humid and dry weather.
• The spores are spread by the wind to healthy plants.
• They cause leaf yellowing, dwarfing, stunting and deformation.
• Common on roses, zinnias, phlox, lilacs, cucurbits, apples and grapes in shaded, crowded areas.




Spray infected plants with a fungicide containing benomyl, or dust them with sulfur. These fungicides protect the new, healthy foliage by killing the mildew spores as they germinate on the leaves, they do not eradicate the fungi on leaves that are already diseased.


If practical, pick off infected leaves. Remove severely infected plants. Spray or dust at regular intervals of 7 to 10 days.



Seasonal plants and flowers

Fernlea grows flowers and plants for all seasons. Choose a category below to see what is available and to find lots of growing and plant care tips.



Annual Plants and Flowers

Container Gardens

Autumn Flowers

Trailing Vines

Red Star Spikes

Rio Dipladenias



Tips and ideas for your garden

Here are some quick links within our site to help you with your gardening.



Selecting Colours

Plant Disease

Plant Pests and Insects

Deer Repellents

Plant Nutrients

Sun vs. Shade Plants

Hardiness Zone Map

Horticultural Glossary

Soil Smarts

Weed Control





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