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-JA- 



DIAGNOSTIC UPDATE 



Once again, the lack of rainfall is 

 causing problems for non- 

 irrigated outdoor plants. Although 

 we had abundant moisture during 

 the first half of the growing season, 

 less than one inch of rain fell from 

 late July through August, and the 

 rainfall from Edouard did little to 

 alleviate the problem. Woody plants 

 in particular have been very suscep- 

 tible to low-moisture conditions due 

 to last year's drought. Maples have 

 been exhibiting tip dieback and 

 marginal leaf scorch, small twigs on 

 hemlocks are yellowing and abscis- 

 ing, and pines are exhibiting 

 heavier-than-normal fall needle 

 drop. (Please refer to the diagnostic 

 update in the October/November 

 1995 issue of The Plantsman for addi- 

 tional information on drought stress 

 symptoms.) 



Although the lack of rainfall kept 

 many of the typical 'summer dis- 

 eases' in check, there were still 

 plenty of disease problems thanks 

 to high humidity and irrigation. 

 BOTRYTIS was a problem on many 

 flowering plants. Rhizoctonia root 

 ROT was diagnosed on hemerocallis, 

 vinca and chrysanthemum, and 

 SCLEROTINIA ROOT ROT was diagnosed 

 on bellflower. Plant bug feeding in- 

 jury was a common problem during 

 late July and early August on a wide 

 range of herbaceous plants. The 

 damage is evident near the tops of 

 the plants as small, clustered brown 

 spots. 



Turf diseases such as brown 

 PATCH and PYTHIUM BLIGHT were com- 

 mon during July and early August. 

 Heat and drought stress caused 

 problems again this year, particu- 

 larly in shallow or sandy soils. An- 

 THRACNosE was a common problem 

 on stressed turf. Summer patch was 

 diagnosed on two turf samples in 

 the last month, and leptosphae- 

 RULINA LEAF BLIGHT was common on 

 turf that had been irrigated at night. 

 Leaf rust was also prevalent on 

 home lawns. 



Symptoms resulting from spring 

 infections by RHIZOSPHAera began to 

 appear on spruce needles in mid- 

 August. The needles on white 

 spruce turn brown while those on 

 blue spruce usually appear purplish. 

 Remember, the key time to control 

 rhizosphaera needlecast is during 

 needle emergence in the spring and 

 again in late August to mid-Septem- 

 ber. Several juniper samples were 

 received with kabatina twig blight 

 and one with PHOMOPSiS tip blight. 



jemember that late autumn 



is the key time for fungicide 



control of SNOW MOLD on turf. 



Also, the turf should continue to 



be mown until growth ceases. 



Two viruses new the UNH-PDL 

 were diagnosed: alfalfa mosaic vi- 

 rus on tomato and bushy dwarf vi- 

 rus on raspberry. The alfalfa mosaic 

 virus caused slight growth distortion 

 and yellowing of the youngest 

 leaves. The raspberry infected with 

 the bush dwarf virus was stunted 

 and exhibited mottling of the leaves. 



What diseases can we expect 

 during the next couple of months? 

 Since there is an abundance of 

 typhula inoculum present in turf- 

 grasses, we can expect problems 

 with snow mold again this winter. 

 Remember that late autumn is the 

 key time for fungicide control of 

 SNOW mold on turf. Also, the turf 

 should continue to be mown until 

 growth ceases. 



Greenhouse crops should be 

 scouted for downy mildew on snap- 

 dragons, (gray fungal growth on the 

 undersides of the leaves), powdery 

 mildew on poinsettias (small chlo- 

 rotic or yellow lesions on the upper 

 surface of the lower leaves with 

 white to gray fungal growth beneath. 

 It is good practice to carry a small 

 zip-loc bag around to put infected 



or suspicious leaves in. 



The most important thing to con- 

 sider during the next two months is 

 preventative measures to reduce 

 the impact of diseases next season. 

 Sanitation is the most important. Re- 

 move all crop debris and destroy it 

 if you know that diseases have been 

 a problem in the past. Composting 

 often does not kill the pathogen in 

 the debris, thus, when it is used as 

 a mulch, the pathogen is reintro- 

 duced into the crop. Be sure to pro- 

 tect woody ornamentals against win- 

 ter damage and desiccation. 



If you wish to submit plant material to the 

 UNH-PDL for diagnosis, send samples 

 {with a check for $12.00) to-. The UNH 

 Plant Diagnostic Lab, CIO Dr. Chergl 

 Smith, Plant hiologij Department, 241 

 Spaulding Hall, UNH, Durham, NH 

 03824. Samples should be accompanied 

 by an identification form {available from 

 your county Cooperative Extension office). 

 Cheryl Smith is the UNH Cooperative 

 Extension Specialist in Plant Health, and 

 can be reached at (603) 862-3841. 



How About Herbs 



Continued from Page 28 



by furry capsules that do not ma- 

 ture until nearly a year later, when 

 they burst and scatter the seed. 

 Medicinal extract has been obtained 

 from the bark of witch hazel for cen- 

 turies. Although most commonly 

 found in the woodlands of New En- 

 gland, when grown in good soil and 

 in the open, this shrub will become 

 a fine, well-shaped specimen. I 

 think it is at Tower Hill Botanical 

 Garden in Boylston, Massachusetts, 

 that 1 have seen a nice specimen 

 plant and I'm sure it's at the Arnold 

 Arboretum as well. 



Tanya ]ackson, a well-known local 

 herbalist, can be reached at 

 603-431-6774. 



OCTOBER'4'NOVEMBER 1996 



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