6 Best Fungicide For Hollyhock Rust | No More Orange Spots

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A three-in-one neem oil concentrate that tackles fungus, aphids, and spider mites with one spray.

If you garden organically and hate juggling multiple bottles, this concentrated solution simplifies your routine. Rose Rx uses clarified hydrophobic extract of neem oil as its active ingredient (a plant-based oil pressed from neem tree seeds), which is approved by the USDA for organic gardening. That means you can spray it on hollyhocks growing right next to your tomato plants without worrying about chemical residues. It kills fungal diseases like black spot, powdery mildew, downy mildew, anthracnose, rust, and leaf spot — all the troublemakers that plague a cottage garden.

Owners mention mixed results. One reviewer noted “I’ve done several applications, and it seems to be getting better,” while another called it “better than all the many products I’ve used,” despite smelling terrible. Weighing 1.1 lb, it is 10% heavier than the 1 lb Eagle 20EW above, which makes sense given the added insecticide and miticide components. The neem oil base is nontoxic to humans, a fact one gardener with a small child specifically appreciated.

Do not expect instant results — neem oil is a preventive and slow curative, so you need consistent weekly applications during the growing season. The smell is strong but fades quickly, and the concentrate dilutes significantly, making each bottle last multiple seasons if you only treat a small patch of hollyhocks.

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A concentrated chlorothalonil solution that makes up to 64 gallons of ready-to-spray fungicide.

When rust threatens your whole flower bed, Ortho MAX delivers a massive volume of protection from a single 16 fl oz bottle. Its active ingredient, 29.6% chlorothalonil (formerly known as Daconil, a broad-spectrum synthetic fungicide), stops and prevents leaf spots, rust, blights, fruit rots, mildews, scab, and molds on vegetables, fruits, roses, flowers, shrubs, and ornamentals. The concentrate makes up to 64 gallons of diluted spray, which is an enormous volume compared to the ready-to-use 20 fl oz Nature’s IQ bottle (a 3.2x value gap when diluted).

Buyers share success stories: “Applied Ortho 3 times (once a month) with very positive results and fully recovered pines/shrubs.” Another reviewer with black spot on roses said the product cured the problem after neem oil had failed. At 20.48 ounces, this bottle is 90% heavier than the 10.8-ounce Monterey Liqui-Cop, and the extra weight comes entirely from the concentrated active ingredient, not filler water.

The catch is that chlorothalonil is a synthetic broad-spectrum fungicide — it can burn delicate foliage if applied in direct sun or at high temperatures. You also need to mix it accurately with a hose-end sprayer, which adds a step compared to the ready-to-use Nature’s IQ trigger spray.

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A ready-to-use copper soap spray with a mist mechanism that coats every leaf crevice.

The standout is the convenience of grabbing a bottle and pulling the trigger. Nature’s IQ Copper Fungicide is a ready-to-use 20 fl oz spray that requires zero mixing, measuring, or hose-hookup. Its innovative spray mist technology is designed to deliver more complete and uniform foliage coverage — meaning the copper soap reaches the undersides of hollyhock leaves where rust pustules first appear. It controls powdery mildew, black spot, rust, blight, and other listed diseases on roses, flowers, ornamentals, fruits, and vegetables.

Customers note that on a badly infected rose bush, “two applications later, there is not a trace of black spot.” Another reviewer noted “the spray mechanism really makes application a breeze.” With a liquid volume of 20 fl oz, Nature’s IQ holds 2.5x more ready-to-use solution than the 8 fl oz Monterey Liqui-Cop concentrate — and you do not have to add water. However, because ready-to-use sprays are mostly water, the amount of copper active ingredient per spray is lower than a concentrate like Eagle 20EW, meaning you may need more frequent reapplication.

One reviewer specifically said they will order again for their hollyhocks and tomatoes, which directly confirms this product targets exactly the plant you are dealing with.

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A rain-fast copper gel concentrate that stays put through spring downpours.

Rain is the enemy of most fungicides, washing them off before they can do their job. Monterey Liqui-Cop uses a gel formulation that is extremely rain-fast once it dries — so you can spray it knowing that April showers will not undo your effort. This concentrate must be mixed with water and applied as a spray, but it includes a measuring spoon to make the mixing process simple. It prevents anthracnose, brown rot, blight, downy mildew, leaf spot, and rust on fruit trees, nut crops, vegetables, and ornamentals.

Reviewers point out that “this has helped with rust on the leaves of my peach and nectarine trees,” and one called it “a very very small product but great product,” remarking on its diminutive 8 fl oz bottle. Compared to the 20 fl oz Nature’s IQ ready-to-use spray, the Liqui-Cop holds 2.5x less liquid volume — but it is a concentrate, so each ounce of this product goes much further when diluted. At 10.8 ounces item weight, it is significantly lighter than the 20.48-ounce Ortho MAX concentrate (a 90% lighter gap).

The catch is that copper fungicides are preventive, not curative — the label explicitly states they must be applied before infection to form a complete protective barrier. If your hollyhocks already have orange pustules, this will stop the spread but may not eliminate existing rust.

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A living biological fungicide that colonizes roots to stop rust before it starts.

This is a completely different approach to hollyhock rust. Instead of coating leaves with copper or chemicals, Monterey Complete Disease Control uses a beneficial bacterium (Bacillus amyloliquefaciens, a naturally occurring microbe) that colonizes the root hairs of the plant. By establishing a living barrier on the roots, it prevents disease-causing fungi and bacteria from gaining a foothold in the first place. It works as both a root drench and a foliage spray, making it among the most versatile organic solutions available — and it is OMRI Listed for organic gardening, meaning it complies with the USDA’s National Organic Program.

Shoppers say that it is “essential to growing tomatoes, cucumbers, and melons in our hot wet summers,” controlling fungal and bacterial diseases when used “at light dilution with kelp for seeds, heavier for transplanting.” At 1 gallon (128 fl oz), this bottle dwarfs every other option on this list — it holds 16x the 8 fl oz of Monterey Liqui-Cop — so it will last multiple seasons even in a large garden. The package ships at 8.47 pounds, reflecting the sheer volume of biological product you receive.

The trade-off is that biological fungicides require consistent reapplication to maintain the bacterial population, especially after heavy rain. One reviewer gave it only 3/5 stars, reporting “challenges getting plant scorch controlled,” which suggests it works best as a preventive foundation rather than a rescue treatment for an advanced rust outbreak.