The exceptionally wet and cool start of the 2013 growing season has set the stage for landscape plants to be vulnerable to various fungus diseases. Phytophtera, mildew, anthrachnose, black spot, septoria leaf spot, verticillium wilt and other fungus infections may be more prevalent this year due to the unusual weather.
Prevention or reduction of these plant problems is possible in several ways. Promoting good air circulation can help a lot. Spacing plant materials farther apart can allow plants of all kinds to dry out more quickly after rains or heavy dew have gotten foliage wet.
Clearing weeds, brush and physical obstructions away so there is better wind flow and sunlight penetration can also help quite a bit. Clean up and removal of leaves, stems and needles that have previously suffered fungus infections can be quite helpful.
Sometimes removal or pruning of trees or shrubs that are overgrown, or too numerous can really help air flow and sunlight availability for plant materials on which you place a higher value.
Yet another way to prevent various types of fungus infections is to apply substance to the surface of the leaves and stems. Fungicides are available for this purpose in a number of formulations using different active ingredients. Chemical companies manufacture fungicides that are frequently used in agriculture, and sold in smaller packages for retail sales to private homeowners. These fungicides employ several different modes of action depending on the chemical formulation, and are generally very effective at preventing infection when sprayed early enough in the cycle of fungus development. Usually applied as a spray and sometimes as a powder or dust, these fungicides can be very effective when deployed in a timely fashion.
Property owners who prefer an organic approach may wish to use fungus control products advocated by the organic movements. There appears to be quite a bit of diversity of opinion on which products work well that are considered organic. When these products do work well, I suspect it is because they contain a chemical that inhibits fungus growth. The difference may be in the source of the chemical.
Products that are considered organic often contain chemical compounds that come from plants and inhibit growth of pests like fungus or insects. Other naturally occurring substances are used that contain other compounds that inhibit pest growth and development, and are considered organic.
Some of the same or similar pest inhibiting substances are manufactured by chemical companies and placed into formulation and packaging convenient for home use. When manufactured by chemical companies, these products are generally not considered organic, and fall within the broad category of commercial pesticides.
Choose what fits and feels best for you. Effectiveness may vary, and the longer you wait the more difficult it becomes to prevent or control plant diseases.