Diplodia tip blight (INJECTION vs SPRAYING) treatments
Hello. We have eleven (diseased) pine trees on our Condo Association Commons area. Two arborist services have given a diagonis of diplodia tip blight. Treatment by company (a) said they would INJECT a solution into the cambria around the base of the tree one foot above the ground.The injected solution would then be taken internally to help the tree. Cost starts at $112 per (6" diameter) tree. Application would last two years. Treatment by company (b) said they would SPRAY all eleven for $175 ($16 per tree). Three separate applications will be needed. Because our trees are in such a bad condition, a yearly spraying program would be appropriate until the disease gets under complete control. We are trying to make an informed decision. The cost-only approach says company (b) should be selected. Unfortunately, we are uncertain about the optimum PROVEN effectivess of SPRAYING verses INJECTION. Request your insight.
Wayne County Michigan
A spray program that covers new buds/grow in spring, thoroughly, and is repeated 2-4 times according to the label, until shoots are full sized, is effective treatment. The critical things are timing it correctly and using the correct fungicide. This treatment will need repeating each year that has wet spring conditions. According to MSU Extension "Diplodia Tip Blight-The sprays must be applied three times in a season to achieve good control: when buds begin to swell and elongate, just before the new needles emerge from the sheath, and 10 to 14 days later. The time this happens will vary every spring, depending on weather. Affected trees should also be mulched lightly and watered (with soaker hoses- to keep branches dry) during periods of dryness to reduce stress on the tree. If caught early, this disease can be managed. However, as the disease progresses, it further weakens the tree and damages its aesthetic value."
Here is an article that describes timing and effective chemicals. Verify that your spray service uses this technique:
You should also rake up as many needles and cones as possible and dispose of these, to minimize the overwintering spores. Clip off all dead needles, too, sanitizing the clippers between cuts. Then mulch with 2-3 inches of fresh material like shredded or chipped bark.
My references indicate that research is still ongoing for injected fungicides. Results have been mixed. Here is one example dated April 2017 (see last paragraph at the bottom):
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