D I A G l\ O S T 



UPDATE 



□ 



H 



azy, hot, and humid ... it sure 

 seemed like we skipped spring. 

 And to add insult to injury, drought 

 conditions prevailed as well. We did 

 get some minor relief from the 

 drought with the thunderstorms in 

 early July, but they brought another 

 set of problems thanks to the dam- 

 aging winds! Although we didn't 

 have a repeat ot last year's wet 

 June, the hot, humid weather has 

 caused many of our 'typical' sum- 

 mer diseases to appear early, par- 

 ticularly on turfgrass. 



The high humidity and warm 

 evening temperatures favored the 

 development oi turf diseases such as 

 brown patch and pythium blight. 

 Pythium also caused significant 

 problems on newly seeded lawns be- 

 cause of the need for frequent irri- 

 gation (thus wet foliage for ex- 

 tended periods). It is important to 

 remember to avoid excessive nitro- 



gen use during warm, humid 

 weather. Also, avoid mowing wet 

 turf since this will easily spread 

 pythium and other foliar diseases. 



Drought-stress symptoms began 

 to appear on many woody plants in 

 mid-June. Marginal browning (ne- 

 crosis) was the most common symp- 

 tom noted on maples, dogwoods 

 and lilacs. Leaf yellowing and early 

 leaf drop were also common on 

 birches (similar to last summer). 

 Drought stressed trees and shrubs 

 will be more susceptible to winter 

 injury, fungal tip blights, cankers, 

 and insect attack. It's important to 

 water trees and shrubs during 

 drought, particularly those in a 

 lawn setting where the grass com- 

 petes for the available moisture. A 

 soaker hose or regular garden hose 

 set a slow trickle should be used to 

 provide a minimum of one inch of 

 water per week. 



A late frost in early May caused 

 damage to many trees including 

 crabapple, dogwood, lilac, and fir. 

 Several fir samples received by the 

 Plant Diagnostic Lab (PDL) were 

 diagnosed with phomopsis canker at 

 the soil line. The canker was initi- 

 ated during late spring frosts last 

 year (1998). The frost-injured tissue 

 is easily colonized by phomopsis, re- 

 sulting in a girdling canker. We can 

 expect to see similar cankers next 

 year thanks to the late frost this year. 



One would think that fungal and 

 bacterial diseases would not be a 

 problem due to the lack of rainfall. 

 Unfortunately, that hasn't been the 

 case. The little rainfall that we did 

 receive occurred at just the right 

 time (during leaf and shot expan- 

 sion) for infections to occur. 

 Gymnosporanguim rusts are preva- 

 lent again this year, although not 

 quite as dramatic as last. Cedar- 



New HampshireA^ermont 



CHRISTMAS TREE ASSOCIATION 



Wreaths * Trees ^ Boughs ^ Cones 



Over 200 Members Over 150 Growers 



Christmas Trees Christmas Wreaths 



44 Years of Service 



For a FREE brochure 

 of wholesale producers and vendors contact: 



Kristina M. Onofrio, Secretary/Treasurer 



326 Baptist Hill Road 



Lunenburg, Vermont 05906 



802-892-7783 



AUGUST/SEPTEMBER 1999 



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