Needlecast on blue spruce; Imicide on Siberian elm - Ask Extension
The tree care contractor at our condo deployed Mauget imicide capsules on mature Siberian elms that appear generally healthy. Are they treating a resi...
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Needlecast on blue spruce; Imicide on Siberian elm #935623
Asked June 15, 2026, 4:52 PM EDT
The tree care contractor at our condo deployed Mauget imicide capsules on mature Siberian elms that appear generally healthy. Are they treating a resistant tree for Dutch elm disease? Or is there another likely use case for systemic injections?
The same company is foliar spraying a large blue spruce, ostensibly for needle cast. I do not see evidence of this disease, though I am no expert (I am an entomologist). The applicator indicated that the application was preventative. Is this recommended for spruce?
Washtenaw County Michigan
Expert Response
Hello, Mr. Cappaert,
The capsules appear to be imidacloprid, which is likely targeted to kill the beetles that spread Dutch elm disease.
Blue spruce are often affected by needlecast as they are native to the dry foothills of Colorado. The humid air in Michigan is very conducive for the spread of the fungal disease. Therefore, the spray is likely preventative; once it is noticeable, the damage is hard to conceal.
Thank you,
-Julie
The capsules appear to be imidacloprid, which is likely targeted to kill the beetles that spread Dutch elm disease.
Blue spruce are often affected by needlecast as they are native to the dry foothills of Colorado. The humid air in Michigan is very conducive for the spread of the fungal disease. Therefore, the spray is likely preventative; once it is noticeable, the damage is hard to conceal.
Thank you,
-Julie
