ANTHRACNOSE.

Anthracnose is commonly seen during wet, cool springs.  It is a fungal leaf infection that causes browned or blackened areas on leaves, distortion of leaves and noticeable leaf fall in the spring.  In some trees, it can cause significant thinning of the canopy and can be a real nuisance for homeowners with the necessity of cleaning up leaves in the spring.  Cr

Anthracnose seldom needs any specific treatment, but if it is severe, fungicide injections may be warranted. 

Sycamore trees that have anthracnose year after year can be treated preventively with fungicide injections in late summer or fall to control the disease the next spring.  With Alamo injections we often see two years of control after a single injection.  With Arbotect injection, we have seen three to four years of control.

CRABAPPLE SCAB

Crabapple scab often causes severe defoliation of crabapple trees.  The lesions form on the leaves in May and June and defoliation begins in July, becoming severe in August, especially with hot dry weather.

Sprays can control scab if early systemic fungicide sprays are applied (twice before the bloom). If sprays are not feasible or if sprays do not adequately control scab, injection of the same fungicide (propiconazole) can be helpful. 

In many cases, we have seen up to two years of control of scab with one injection in late summer or early fall.

DUTCH ELM DISEASE

Dutch Elm Disease is still with us and kills many nice American elms each year (Siberian elms have resistance).  This disease can be prevented with a high degree of success eith injected fungicides. 

Alamo can give one to two years of control and Arbotect can give two to three years of control.  For highly valued trees, we suggest the shorter retreatment interval.

If Arbotect is selected, we suggest treating the first year with Alamo and then if the tree is nice and healthy the next year, treat with Arbotect.  Since we do not know if a tree has been inoculated, the Alamo may have more therapeutic action and it is less expensive to treat with.  Following is a table of relative attributes:

CHEMICAL                                    DURATION                    EFFECTIVENESS                         COST

Alamo (propiconazole)               One to two years          about 95% (estimated)                 $10 to $12 per diameter inch

Arbotect (thiabendazole)            Two to three years       99% (observed)                              $25 per diameter inch

The reason Arbotect is so much more expensive is because it is a more expensive chemical and because it must be infused with large volumes of water (20 to 50 gallons) and the infusion can take several hours.  It usually only takes 30 to 60 minutes to treat a tree with Alamo.