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…]

Unfortunately, this one is another bug.

Pine Sawfly Larval Case
Photo by Jim Johnson

The pine sawfly is normally kept under control by natural predators so I rarely see them. This, however, was my second sighting in the last 4 months so I guess environmental conditions have not be optimal for predator survival.

Keep a lookout for these insects. The larvae are voracious eaters that completely devour the needles and can totally defoliate pine trees. The first site I visited had a block of about 25 trees more than 20 feet tall that were without needles.

If treatment is necessary, first generation control will need to occur from mid-May to mid-June. The second generation is active in the July to August time period. Cornell University Cooperative Extension of Suffolk County put together a good review of pine sawflies. It can be found at:
http://ccesuffolk.org/assets/Horticulture-Leaflets/Pine-Sawflies.pdf