Issues in Choosing Fungicides
Fungicides do not cure fungal diseases. They are most useful in preventing mildews and rusts that attack plant foliage from spreading to healthy foliage. When you spray healthy foliage with a fungicide, spores have difficulty attaching themselves to it. The sprays must be repeated frequently and faithfully after rains and to protect new foliage growth as it emerges.
A general garden fungicide is useful for those plants that are traditionally afflicted with mildews and leaf spots if you are not prepared to throw them away. These diseases are rarely fatal in mature plants, but they badly mar the appearance of ornamental plants. There are fungicides made from natural ingredients and fungicides made from synthetic ingredients; both groups are effective if used properly according to their label.
How to Use Fungicides
Fungicides are much less effective once a disease has become well established, so for best results use them early in the season. Spray even before you see evidence of damage on plants with chronic mildew or rust problems. Plan to repeat fungicide treatments every week or 10 days throughout the season to prevent a leaf fungal disease from developing or spreading.
Thorough coverage is critical because, whether you use a dust or a spray, only those parts of the plant that are actually coated with the fungicide are protected. Problems on individual plants can be handled with ready mixed fungicide product sold in its own applicator bottle. For many infected plants or large trees or shrubs plants, you may need up to 2 gallons of spray. In that case, purchase a concentrated form of fungicide and mix it with water yourself according to package label instructions. For serious disease problems on large shade trees, seek professional help from an arborist. For information about pump sprayers click Here.
Some Tricks For Success
Fungicides are often more effective if applied using an additive called a "spreader-sticker" or "wetting agent" which helps the fungicide adhere better to the foliage being sprayed.
When you finish your spray job it is wise to use a commercial sprayer cleaner to be sure there is absolutely no residual fungicide when you again use that same sprayer for a different pesticide product. For information on these two products Click Here