Cur­ing the Colorado spruce blues

Winnipeg Free Press - Section F - - HOMES - MICHAEL ALLEN

OVER the years, in this col­umn I have writ­ten about the prob­lems as­so­ci­ated with spruce trees. I have men­tioned tip blight fun­gal dis­ease has been in­creas­ing an­nu­ally over the past few years. In 2012, I said that year was the worst I have seen in 40 years. Sadly, the dis­ease has pro­gres­sively wors­ened in 2013 and in 2014. Sci­en­tif­i­cally, the dis­ease is known as Siro­coc­cus coni­genus. This spring, I have no­ticed Colorado blue spruce has been hit hard by this dis­ease. Dam­age con­tin­ues to be worse in spruces out­side of Win­nipeg. The lower half of the tree is es­pe­cially tar­geted by this dis­ease. Heav­ily dis­eased trees are al­most dead as they can­not eas­ily re­cover from se­vere in­fec­tions of this dis­ease.

The dis­ease tar­gets older and larger Colorado spruce trees. Ef­fec­tive treat­ment be­comes al­most im­pos­si­ble on these ma­ture trees, while the in­fec­tion is very light and treat­able in smaller and younger spruces.

How do you rec­og­nize spruce tip blight dis­ease?

This fun­gal dis­ease causes slightly or promi­nently curled ends of the twigs usu­ally de­nuded of their nee­dles ex­cept on one side start­ing in late May or June. Advanced in­fec­tions will turn the nee­dles orange or rusty brown in colour. In re­cent years, a sec­ond in­fec­tion pe­riod will likely oc­cur later in July or Au­gust.

Bright yel­low-green dis­coloura­tion of the newer nee­dles in parts of the tree, are of­ten early overlooked signs of this dis­ease. This dis­coloura­tion is likely to ap­pear in late spring, sum­mer or early fall. The colour pat­tern can per­sist over winter and show up in the spring. A small area of Colorado blue spruce twigs near the end of the boughs can have sev­eral dif­fer­ent colour pat­terns: blue, green, bright green-yel­low, yel­low, orange, and rusty brown. This pat­tern changes from year to year. The dis­ease oc­curs in a tree at dif­fer­ent stages of ma­tu­rity. These stages are char­ac­ter­ized by the colour pat­terns above. Ul­ti­mately, all the nee­dles turn a rusty brown and fall from the tree. How is the dis­ease treated? The en­tire tree should be spray treated with an ap­proved fungi­cide such as cop­per, weather per­mit­ting. Usu­ally two or three spray treat­ments of cop­per about two weeks apart are nec­es­sary in the spring and early sum­mer (May to July), and again with a sin­gle fungi­ci­dal spray in late July to early Au­gust. This year’s on and off wet weather and strong winds are pre­vent­ing the proper treat­ments of the dis­ease. Main­tain­ing a large Colorado spruce can be an ex­pen­sive un­der­tak­ing and can pro­duce lo­cal­ized en­vi­ron­men­tal con­cerns through fungi­cide spray­ings.

One year of treat­ment is not suf­fi­cient to con­trol the dis­ease. The fungi­cide should be ap­plied con­sec­u­tively in the sec­ond and third years as well. For heav­ily in­fected trees, a fourth and fifth year of con­sec­u­tive spray­ing will be nec­es­sary.

As I have said many times be­fore in this col­umn, proper fer­til­iza­tion of trees over sev­eral con­tin­u­ous years can im­prove a tree’s ca­pa­bil­ity to con­tain se­ri­ous fun­gal dis­eases. This will be the sub­ject of my next col­umn. Michael Allen is a con­sult­ing ur­ban forester and cer­ti­fied I.S.A. ar­borist and owner of Vibur­num Tree Ex­perts. He makes house and gar­den vis­its to as­sess tree and shrub prob­lems. He can be con­tacted by call­ing 831-6503 or by e-mail at vibur­ Ques­tions can be mailed to Michael Allen, c/o News­room, Win­nipeg Free Press, 1355 Moun­tain Ave., Win­nipeg, MB, R2X 3B6. His web site is www.tree­ex­


The dis­ease Siro­coc­cus coni­genus tar­gets Colorado blue spruce trees.

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