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 shiny and sunny addition to your backyard.

When supplied with optimum rising circumstances, these stunning and vibrant flowers aren’t susceptible 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 methods to plant and take care of Helianthus.

Whether or not you’re rising cute little teddy bear varieties or black oil sunflowers for the birds, this text will focus on seven frequent ailments that may smash 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 certainly to seem in heat, humid circumstances, particularly after rain as moisture is a major driver of illness growth.

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

The spots will finally merge and develop in dimension, finally protecting nearly all of a leaf. In time, contaminated specimens will lose their leaves – typically the decrease leaves first – and finally die.

The pathogens can unfold through 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 sufficient air circulation, pruning symptomatic foliage, and watering at soil stage might help curb the unfold.

If a majority of your vegetation are contaminated, you’ll want to drag them up and eliminate them within the trash, not on the compost pile.

For those who’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 a few years.

2. Downy Mildew

Many alternative species can endure from a wide range of completely different mildews, however this taste of downy mildew – attributable to 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 turn out to be contaminated and often 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 vegetation don’t die, they’ll endure from stunted progress and decreased 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 vegetation are contaminated, take away and eliminate these specimens within the trash.

3. Phoma Black Stem

Also called Phoma blight, Phoma black stem has one very apparent symptom – I’m positive you may determine what it’s.

This illness is attributable to the fungus Phoma macdonadlii, which survives in seeds or on contaminated crop residue and is unfold by bugs resembling 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, all the 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 could be simply confused with Phoma black stem, for a couple of causes.

Attributable to fungal species within the Diaporthe genus, the pathogens overwinter in plant particles. An infection often 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 shade relatively than black.

Contaminated foliage will develop small brown spots, which finally 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 sufficient airflow between vegetation, clear up crop detritus, rotate your plantings, and for those who’ve had an issue previously, select resistant hybrids.

For management, you need to use copper fungicide when the flower heads have simply shaped. In any other case, take away and destroy severely symptomatic vegetation.

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 through wind or splashing water to new, uninfected foliage.

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

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

Fortunately, this situation is generally a beauty subject, as infections aren’t often deadly.

To stop powdery mildew, guarantee your sunflowers have full solar publicity and make sure to area them aside to permit for adequate air circulation.

Trim away symptomatic leaves as you discover them, and seek the advice of our information to be taught extra about methods 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 through wind to different vegetation. If an infection is extreme sufficient, defoliation can happen.

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

7. Septoria Leaf Spot

Septoria leaf spot illness is attributable to the fungus Septoria helianthi.

This illness tends to develop shortly in heat circumstances and in occasions of excessive rainfall. The pathogen is usually unfold through splashing water, and overwinters in plant residue.

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

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

Diseased foliage results in decreased photosynthesis, which leads to decreased progress.

To stop Septoria leaf spot, rotate your plantings each three years at the least, keep away from splashing the leaves with water whenever 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 vegetation are contaminated, pull them up and eliminate 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 could be averted by rising these annuals in a full solar location, sustaining sufficient airflow between vegetation, and watering at soil stage as an alternative of from overhead.

At season’s finish, clear up beds and borders to stop 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:

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