How to Identify and Manage Common Sunflower Diseases

Sunflowers, Helianthus annuus, are annuals within the Asteraceae household appropriate for cultivation in Zones 2 to 11.

Whether or not you develop them for his or her decorative worth or the edible seeds, these flowers are a vivid and sunny addition to your backyard.

When supplied with optimum rising circumstances, these lovely and vibrant flowers aren’t vulnerable to many plant ailments, however you’ll must know what to search for if pathogens do come to go to.

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In our information to rising sunflowers, we cowl learn how to plant and take care of Helianthus.

Whether or not you’re rising cute little teddy bear sorts or black oil sunflowers for the birds, this text will talk about seven frequent ailments that may wreck the floral show.

Right here’s the lineup:

1. Alternaria Leaf Blight

Attributable to the fungal species Alternaria helianthi or A. zinniae, Alternaria leaf blight is most probably to seem in heat, humid circumstances, particularly after rain as moisture is a primary driver of illness improvement.

Contaminated specimens will exhibit small, darkish, typically yellow-ringed spots on the foliage, usually alongside the margins or in the direction of the leaf ideas.

The spots will ultimately merge and develop in dimension, ultimately masking the vast majority of a leaf. In time, contaminated specimens will lose their leaves – typically the decrease leaves first – and ultimately die.

The pathogens can unfold by way of wind or splashing water, be seedborne, survive in weed hosts, and overwinter in crop detritus or the soil. And even when an contaminated sunflower doesn’t die, having blighted foliage received’t assist a sunflower to develop its beautiful blooms.

Sustaining applicable spacing to advertise ample air circulation, pruning symptomatic foliage, and watering at soil degree might help curb the unfold.

If a majority of your crops are contaminated, you’ll want to tug them up and get rid of them within the trash, not on the compost pile.

In the event you’re rising sunflowers as a canopy crop, within the case of an infection ensure you rotate your crops and don’t plant Helianthus in the identical spot for 2 to 3 years.

2. Downy Mildew

Many various species can undergo from quite a lot of completely different mildews, however this taste of downy mildew – brought on by the fungus Plasmopara halstedi – is definitely distinctive to Helianthus.

Able to surviving in soil for as much as a decade, P. halstedi thrives in cool temperatures, excessive humidity, and waterlogged circumstances.

If these circumstances are current throughout seed germination and seedling emergence, younger specimens grow to be contaminated and normally die shortly.

If these juveniles make it to maturity, they’ll lack vigor and customarily exhibit chlorotic leaves with white cottony progress on the undersides. If contaminated crops don’t die, they’ll undergo from stunted progress and lowered seed set.

Rising resistant sunflower varieties and buying licensed disease-free seed might help you keep away from an infection.

Foliar fungicides received’t do a lot, although. In case your crops are contaminated, take away and get rid of these specimens within the trash.

3. Phoma Black Stem

Also called Phoma blight, Phoma black stem has one very apparent symptom – I’m certain you’ll be able to work out what it’s.

This illness is brought on by the fungus Phoma macdonadlii, which survives in seeds or on contaminated crop residue and is unfold by bugs reminiscent of sunflower stem weevils, Apion occidentale.

And as with many fungal circumstances, moist climate promotes the event of this illness.

As soon as contaminated, the plant will exhibit one- to two-inch black lesions on the stems. Extra darkish spots can present up on the foliage and flowers, the complete plant can droop and dry up, and flowers can die.

Cleansing up plant residue at season’s finish, rising hybrid species, and rotating your sunflowers each three years might help keep away from this illness, together with managing the native pest populations.

Fungicides received’t do a lot for management, so it’s greatest to take away and pitch contaminated specimens.

Keep away from planting sunflowers in the identical location the next season.

4. Phomopsis Stem Canker

This illness will be simply confused with Phoma black stem, for a number of causes.

Attributable to fungal species within the Diaporthe genus, the pathogens overwinter in plant particles. An infection normally happens throughout moist circumstances like moist climate and excessive humidity.

And it additionally produces gnarly stem lesions – though they’re bigger than these of Phoma black stem, and brown in coloration fairly than black.

Contaminated foliage will develop small brown spots, which ultimately merge into giant brown sections of foliar decay. Along with trying nasty, contaminated specimens are fast to wilt and die.

To stop this illness, guarantee ample airflow between crops, clear up crop detritus, rotate your plantings, and should you’ve had an issue prior to now, select resistant hybrids.

For management, you should utilize copper fungicide when the flower heads have simply shaped. In any other case, take away and destroy severely symptomatic crops.

As soon as once more, keep away from planting sunflowers in the identical spot the next season and select one thing that doesn’t play host to those pathogens, like wheat or corn.

5. Powdery Mildew

Surviving as mycelium in plant detritus, the fungal pathogen Erysiphe cichoracearum spreads by way of wind or splashing water to new, uninfected foliage.

An infection and illness improvement is most probably in humid climate, but whereas the foliage stays dry.

The principle symptom is leaves coated with a whitish-gray powder. Moreover, foliage may develop small, black specks of spore-producing cleistothecia, which can solely move the issue onto different specimens.

Fortunately, this situation is generally a beauty challenge, as infections aren’t normally deadly.

To stop powdery mildew, guarantee your sunflowers have full solar publicity and you’ll want to house them aside to permit for enough air circulation.

Trim away symptomatic leaves as you discover them, and seek the advice of our information to study extra about learn how to handle powdery mildew.

6. Rust

Puccinia helianthi is the fungal species that causes rust in sunflowers.

The pathogen survives in lifeless and decaying plant matter over the winter and assaults your sunflowers when they’re moist from precipitation or irrigation.

Contaminated sunflowers will exhibit rust-colored, yellow-ringed growths on the foliage which produce spores that unfold by way of wind to different crops. If an infection is extreme sufficient, defoliation can happen.

If signs are extreme, pulling up and disposing of contaminated crops could also be your best choice.

7. Septoria Leaf Spot

Septoria leaf spot illness is brought on by the fungus Septoria helianthi.

This illness tends to develop shortly in heat circumstances and in instances of excessive rainfall. The pathogen is mostly unfold by way of splashing water, and overwinters in plant residue.

Signs embrace water-soaked, rounded greenish-gray lesions on the foliage, that are normally ringed with chlorotic tissue.

In time, small spore-producing spots will even type on the undersides of leaves, and contaminated crops may develop a sad-looking, watery wilt earlier than they die.

Diseased foliage results in lowered photosynthesis, which ends up in lowered progress.

To stop Septoria leaf spot, rotate your plantings each three years not less than, keep away from splashing the leaves with water once you irrigate, and buy licensed disease-free seed.

Cleansing up plant detritus on the finish of the season denies the pathogen a spot to overwinter. In case your crops are contaminated, pull them up and get rid of them within the trash.

Well being Is Wealth, Y’all

It’s true for folks, and it’s true for sunflowers.

Most of those ailments will be averted by rising these annuals in a full solar location, sustaining ample airflow between crops, and watering at soil degree as a substitute of from overhead.

At season’s finish, clear up beds and borders to forestall disease-causing pathogens from overwintering in lifeless plant tissue.

Are you rising sunflowers and have yours suffered from any of those ailments? Tell us within the feedback part beneath!

And for extra details about rising sunflowers in your backyard, learn these guides subsequent: