DOTHISTROMA NEEDLECAST ON PINES OR RHIZOSPHAERA ON BLUE SPRUCE
The needlecast fungi cause second year needles to fall off or be “cast” off, leaving only the current year’s growth of needles. Since most evergreens retain three or more years of needles, the affected branches look thin and bare except for the ends. The disease affects mainly the lower branches, so the top is often fairly normal looking, while the bottom of the tree is practically “see-through.” Before the needles are cast off, they are brown or purplish in color.
TIP BLIGHT (SPHAEROPSIS OR DIPLODIA)
Two needle pines, especially Austrian pines are also susceptible to infection by tip blight fungi. These fungi cause stunting, browning and death of new growth tips, especially on the lower portion of the trees. When severe, the fungus can cause cankers and death of complete branches. The brown tips stay on the tree, causing a lot of brown discoloration of multiple tips and deformed growth of subsequent years’ branch tips.
CYTOSPORA CANKER OF SPRUCE
Cytospora canker occurs mostly on blue spruces in Michigan, causing branch death mainly of lower branches, but also can kill branches in random locations within the tree. There is no specific treatment available. Follow this link for description and recommendations:
GOALS OF TREATMENT
Our goals in treating these diseases are to encourage new growth and protect the new growth from becoming infected. If we can encourage new growth with fertilizer or injected nutrients and then protect the new growth with fungicidal sprays for at least three consecutive years, the tree can return to a healthy normal appearance.
We suggest fertilizing the first year with a sustained release product and then a commitment to a spray program for at least three years. The sprays must be applied at the proper times and with fungicides labeled for the specific disease being prevented. This usually means fungicide sprays in April, early May, late May, and early to mid-June (different regimens for different diseases). Later sprays may be beneficial, especially if a cold spring results in new growth not developing as fast as normal. Unfortunately, most general spraying companies do not apply the specific material at the specific timing needed to control these diseases. Beware of any company that offers sprays after the spring spray window noted above. Be sure that any company you hire is using the product labelled for the fungus targeted (see below).
Rhizosphaera is treated with active ingredient chlorothalonil (Daconil, Fungonil, Ensign 720, others) or copper fungicides (Junction or Kocide or CuPRO). Protect DF is labelled for Rhizosphaera, however another fungicide with the same active ingredient is not, so we have never used that particular fungicide for rhizosphaera. Dothistroma is treated with copper fungicides (Junction or Kocide or CuPRO). As far as we are aware, no other fungicides are labelled for Dothistroma in pines.
Diplodia is treated with sprayed systemic fungicides like thiophanate methyl (Clearys 3336, others) and/or propiconazole (Bannermaxx, others). Some companies offer injection of trees with propiconazole for diplodia. A major study reported in 2009 did not confirm any beneficial effect of injection therapy. Some other treatment trials are underway and we will be trying some treatment trials and will report any results.
Cytospora is treated by general health measures and sanitation pruning, with no sprays OR INJECTIONS available that can control this problem. Be aware that there are some companies or individuals who sell sprays or injections for this problem, but there is no evidence that either would be effective.
Here is a link to a website of Iowa State University that succinctly discusses the treatment for these fungal diseases:http://www.ipm.iastate.edu/ipm/hortnews/2007/4-18/conifer.html
PATIENCE IS REQUIRED
Needlecast diseases require patience and faith in the treatment regimen because it usually takes two years before significant improvement is observable. The needles that are on the tree the first year of treatment are already infected and will fall off, so the tree may look almost as bad one year after starting treatment as it did at the beginning. However, by two years after starting treatment, the tree should have two years worth of needles and be looking much better. By the third or fourth year the tree should be near normal, with a three year blanket of needles by late summer of the third or fourth year of treatment.
SCAB, LEAF SPOT, AND RUST
Many flowering trees, especially flowering crabs and hawthorns are susceptible to scab, leaf spot, rust and other fungal diseases of the leaves.These fungi cause leaf damage, discoloration, holes, spots and often early leaf loss (defoliation).In some cases, so many leaves are lost by mid-August, people mistakenly think the trees are dead. These foliar fungal diseases can be treated with fungicide sprays applied at the right times- just as buds are swelling in the spring, and again in 7 to 10 days when leaves are small and before the bloom. Many fungicides are labelled for scab. We use propiconazole or thiophanate methyl or a combination of the two. Fungicide injections using propiconazole can also give good control.
Infected needles and leaves are the main source for re-infection of the new plant foliage. Removing these sources of infection is helpful.
Excessive wetness and failure to dry out between spring rains helps fungal organisms to become established and multiply.
- Remove fallen leaves or needles to get rid of the infected material.
- Remove the brown blighted branch tips and fallen cones.
- Avoid having automatic sprinklers hitting the trees.
- Anything that helps the trees to dry out between rains can be helpful. Thinning of the branches, removing barriers to air flow such as underbrush, weeds, man-made obstructions to air flow