Fungicide

Fungicides are chemicals or organisms that kill or inhibit fungi and fungal spores. Since fungal diseases are responsible for significant agricultural losses, knowing how to fight these organisms is important.

Peach leaf curl (Kate Russell)

How do fungicides work?

Fungicides work in one of three ways:

• Direct contact - only works where it comes in contact with the plant
• Translaminar - absorbed through upper leaf surfaces and moved to lower surfaces
• Systemic - absorbed into the vascular bundle and moved throughout the plant in the xylem

The effectiveness of any fungicide treatment is far better as prevention than cure. Once a fungal disease takes hold, it can be very difficult to get rid of it.

Fungicide ingredients

Sulfur is a common component of most fungicides, as are neem, rosemary and jojoba oil. Beneficial bacterium (Bacillus sabtilis) and fungi (Ulocladium oudemansii) can be added to these mixtures to improve their effectiveness. Fixed copper and Bordeaux mixtures are also used as fungicides. Over-the-counter fungicides commonly contain cadmium, copper, mercury, and tin, as well as sulfur.


Fungal diseases treated with fungicides

Fungal plant diseases include:

• alternaria blight (Early Blight)
• phytophthora blight (Late Blight)
• cytospora canker
• nectar canker
• rust
• anthracnose (bird’s-eye spot)
• clubroot
• damping-off
• downy mildews
• powdery mildew
• galls
• leaf blister
• leaf curl
• leaf spots
• black spot
• scabs
• smuts
• Fusarium wilt
• Verticillium wilt

Rust on rose leaves (Kate Russell)

Unlike most of these fungal diseases, Fusarium and Verticillium wilts cannot be controlled with fungicides.

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While the use of fungicides can be effective, prevention is a better course of action. One way to reduce the chance of fungal infections is to plant resistant varieties. Another way to avoid fungal infestations is to improve air flow with good pruning, avoid watering from above, which may splash fungal spores onto nearby plants, and by removing and destroying any diseased plant tissue. Ensuring good drainage is another way to reduce the need for fungicides.