In this article:

• Impact & Biology
• Symptoms & Case Example: White pine blister rust
• Management

Where would we be without rusts? Rust diseases, to a plant pathologist, are anything but boring. In fact, this group of plant diseases contains some of the most destructive pathogens of vascular plants. Throughout history, rust epidemics have caused famine and wrecked the economies of entire civilizations. Important food and fiber crops affected by rust diseases include bean and soybean, grains (barley, corn, oat, and wheat), asparagus, cotton, pine, apple, and coffee (coffee rust is particularly troublesome in Guatemala right now). Rust diseases also affect a wide variety of ornamentals – landscape plants, greenhouse and nursery crops, Christmas trees – you name it. [Read more…]

Recent reports bring to mind that warm and wet spring weather is perfect for development of the bacterial disease known as fireblight in susceptible hosts.  Fireblight is caused by Erwinia amylovora, a bacterium that only affects plants in the rose family (Rosaceae).  Some common hosts include apple, crabapple, cotoneaster, hawthorn, mountain ash, pyracantha, and pear.
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Although the disease “downy mildew” sounds similar to the more familiar disease called “powdery mildew,” the downy mildews are caused by fungal relatives called Oomycetes.  These fungal-like organisms, troublesome in during cool, moist weather, attack tender, above-ground plant parts, dispersing rapidly in films of water.  In susceptible ornamental plants, downy mildews are most often caused by species of Peronospora, although species of Plasmopara, Pseudoperonospora, Sclerospora, and Bremia also cause this disease.  [Read more…]

Although the weather this weekend promises to be lovely, recent rains and the likelihood of more to come is ideal for the development of foliar diseases in the landscape.  The most common diseases on trees and shrubs affect the foliage as spots, blotches, and blisters.  Although unsightly, most foliar diseases do not greatly impact the health of the plant, and chemical inputs are rarely necessary.  [Read more…]

Now is the time to monitor for two common diseases of Douglas fir:  Rhabdocline needlecast (caused by the fungus Rhabdocline pseudotsugae) and Swiss needlecast (caused by the fungus Phaeocryptopus gäumannii).  Rhabdocline needlecast is well established in New Jersey Christmas tree plantations, and Swiss needlecast has become more common.  The discriminating grower wants to know, “what’s the difference?” [Read more…]

      It’s the first day of spring…  Consider that roadside vegetation has been exposed to de-icing compounds following several recent late-winter storms.  Runoff from treated pavement contains dissolved salts that can injure adjacent vegetation.  In plants sensitive to excessive salt, affected foliage may scorch and drop prematurely.  In severe cases, the death of twigs, branches, and sometimes the entire plant, may occur.

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