Garden care
Does your garden need a fungicide?
Spots, powder, and wilt on your plants? Here’s how to tell if it’s fungal disease, and what to do about it.
Black spots on your roses, a white powder dusting your crepe myrtle, blotches spreading across shrub leaves, these are the calling cards of fungal plant disease, and they can move fast through a garden if you don’t act. The tricky part is knowing when what you’re seeing is actually a fungus (and treatable with a fungicide) versus a watering problem, a pest, or a nutrient issue. This guide helps you identify common plant diseases and decide whether a fungicide is the right response.
Is it actually a fungal disease?
Fungal diseases tend to share a few visual signatures. If you see these, a fungicide is likely the right tool:
Black or dark spots on leaves, often ringed or blotchy, classic black spot (common on roses) and leaf spot diseases.
White or gray powdery coating on leaves and stems, powdery mildew, which thrives in humid conditions and shows up on crepe myrtles, squash, and many ornamentals.
Orange, brown, or yellow pustules on the undersides of leaves, rust diseases.
Fuzzy gray mold or downy growth, botrytis (gray mold) and downy mildew, often after wet, cool spells.
Green algae or slime on shady garden surfaces, pots, and walkways, an algae problem that some products also address.
If instead you see chewed leaves or insects, that’s a pest, not a fungus, and a fungicide won’t help. Uniform yellowing can be a watering or nutrient issue. When in doubt, look for the spreading, patterned spotting and coatings above, those are the fungal tells.
The golden rule: fungicides prevent, they don’t cure
This is the single most important thing to understand. Most fungicides are protectants, they create a barrier that stops new infection, but they can’t undo damage already done to a leaf. That means the earlier you treat, the better: at the first sign of disease, or preventively when conditions favor it (warm, humid, wet weather). Waiting until a plant is covered means you’re protecting whatever healthy tissue is left, not reversing the spots you already see.
Two fungicide options from Agrisel
The versatile everyday option
Monterey Consan 20
A concentrated three-in-one fungicide, algaecide, and disinfectant. It controls black spot on roses, powdery mildew on crepe myrtles, anthracnose, downy mildew, rust, and algae on garden surfaces, and it can even disinfect pots, tools, and greenhouse benches to stop disease spreading between plants. A little goes a long way, typical garden use is about 2 tablespoons per gallon of water.
Broad garden, ornamental, and hard-surface use · NOT for edibles
For tougher ornamental & tree disease
Chlorosel Pro 720
A professional-grade contact fungicide (54% Chlorothalonil, the same active ingredient as Daconil and Bravo) with a rainfast formula. It controls 100+ diseases, leaf spots, blights, powdery mildew, rust, needlecast on conifers, on ornamentals, trees, shrubs, and gardens. A strong choice when disease pressure is heavy or you’re protecting valued ornamentals and trees.
Ornamentals, trees, shrubs, gardens · NOT for home lawns
Read the label for where each one can go
Two important limits to know before you spray. Monterey Consan 20 cannot be used on edible plants or food crops, keep it to ornamentals, lawns, and hard surfaces. Chlorosel Pro 720 is not labeled for home lawns (or turf at schools, parks, playgrounds, and similar sites); it’s for ornamentals, trees, shrubs, and gardens. For diseased trees, keep Consan 20 applications at least 100 feet from ponds, streams, and other water. Always confirm your specific plant and site are on the label before treating.
How to treat plant disease effectively
Act early. Treat at the first sign of disease or ahead of disease-favorable weather, fungicides protect, they don’t reverse damage.
Cover thoroughly. Contact fungicides only protect what they touch, so coat both the tops and undersides of leaves.
Repeat as directed. Disease pressure usually calls for reapplication, often every 7 to 14 days during active conditions. Follow the label interval.
Improve conditions too. Fungi love wet, crowded, poorly ventilated plants. Water at the base (not overhead), space plants for airflow, and clean up fallen diseased leaves.
Common questions
How do I know if my plant has a fungus or something else?
Fungal disease usually shows as spreading, patterned symptoms: dark leaf spots, a white powdery coating, orange rust pustules, or fuzzy gray mold. Chewed leaves or visible bugs point to pests instead, and uniform yellowing is often a watering or nutrient issue. If you see the spotting and coatings, a fungicide is the right tool.
Will a fungicide cure the spots already on my plant?
No, most fungicides are protectants, not cures. They stop new infection but can’t heal leaves that are already damaged. That’s why treating early, at the first sign of disease or before it starts, matters so much. Damaged leaves won’t recover, but you can protect the rest of the plant.
Can I use these fungicides on my vegetable garden?
Be careful here. Monterey Consan 20 cannot be used on edible plants or food crops, it’s for ornamentals, lawns, and hard surfaces only. Always check the specific product label for whether edibles are permitted and for any pre-harvest interval before using any fungicide on food you’ll eat.
Which one should I choose for my garden?
For everyday garden and ornamental disease, plus the bonus of disinfecting pots and tools, Monterey Consan 20 is a versatile, broadly labeled choice. For heavier disease pressure on valued ornamentals, shrubs, and trees, Chlorosel Pro 720 is the professional-grade option. Match the product to the plant and confirm it’s on that product’s label.
How often should I apply?
During active disease conditions, most fungicides are reapplied on a roughly 7 to 14 day schedule, since the protective coating wears off and new growth is unprotected. Follow the specific interval and seasonal maximum on the product label, and reapply after heavy rain if the product isn’t fully rainfast.
Can I prevent plant disease without spraying?
To a large degree, yes. Most fungal disease is driven by moisture and poor airflow, so water at the base of plants rather than overhead, space plantings for good ventilation, remove and discard diseased leaves, and disinfect tools between plants. Good garden hygiene reduces how often you’ll need to reach for a fungicide at all.
Protect your plants before disease spreads
Contact Agrisel to find a reseller carrying Monterey Consan 20 and Chlorosel Pro 720.