A G N O S T 



UPDATE 



The "strange" weather patterns 

 have continued for much of the 

 growing season (or is it that we're just 

 getting back to "normal" weather?) 

 The following is a sample of some of 

 the problems seen from early )uly 

 through early September . 



Woody Ornamentals 



The immediate and long-term ef- 

 fects of drought continue to be 

 seen not only in New Hampshire 

 but throughout much of the north- 

 east. Fungal cankers and tip blights 

 were the most common visible 

 symptoms Canker diseases diag- 

 nosed during the last two months 

 included cytospora on willow, flow- 

 ering almond and maple; botryo- 

 SPHAERIA on elm, red oak, rhodo- 

 dendron, honey locust, viburnum 

 and Piehs, phomopsis on juniper and 

 holly; and sphaeropsis (diplo-dia) 

 Scots and Austrian pines. The 

 botryosphaeria on red oak is evi- 

 dent as clusters of dead leaves at 

 the tips of branches The dead 

 leaves remain on the twigs through- 

 out the winter. Atropellis canker 

 also seems to be increasing on 

 hard pines, particularly Austrian 

 pines The disease is usually evident 

 as one or more dead branches, often 

 with a slight canker near the trunk. 

 The bark beneath the canker is 

 usually stained a dark greenish- 

 brown. American elms are showing 

 an increase in the incidence of Dutch 

 ELM DISEASE due to the effects of 

 drought. Delphinella tip blight is 

 relatively wide-spread in Christmas 

 tree plantations in NH and VT. 



Once again, kabatina appears to 

 be the most prevalent tip blight 

 problem on junipers. Kabatina, 

 phomopsis, and winter damage all 

 produce similar symptoms, thus 

 identification of the causal agent by 

 symptoms alone is nearly impos- 

 sible. Samples should be sent to a 

 lab for positive identification since 

 the timing of chemical controls for 

 phomopsis and kabatina differ (spring 

 for PHOMOPSIS and late summer for 



kabatinai. Lophodermium needle- 

 cast has also been a common prob- 

 lem on prostrate juniper cultivars. 

 Look for football-shaped, black 

 fruiting bodies on the needles. Sev- 

 eral other needlecasts have also 

 been common problems due to the 

 wet spring (and fall in IQOti); 

 plioderma on Austrian and pitch 

 pines; RHABDOCLINE on Douglas fir; 

 lirula on firs; and lots of rhizo- 

 sphaera on spruce. Rhizosphaera 

 needle blight on firs (balsam and 

 Fraser) seems to be increasing in 

 northern New England. Anthra- 

 CNOSE diseases were widespread 

 this year. Sycamore and ash were 

 particularly hard-hit. Monilinia 

 SHOOT blight was widespread on 

 ornamental Prunus species and was 

 confirmed on flowering quince. 



Herbaceous Ornamentals 



One of the most prevalent diseases 

 on herbaceous ornamentals this sum- 

 mer was PSEUDOMONMAS LEAF SPOT on 



impatiens. This disease is character- 

 ized by red-bordered spots with a 

 light tan-to-white center. Since the 

 disease is caused by a bacterium, 

 rain splash and overhead watering, 

 and poor drying conditions favor the 

 spread and development of the dis- 

 ease. Be sure to remove all crop de- 

 bris from the planting sites and con- 

 tainers, and sterilize all containers 

 before using next season. 



Botrytis was widespread on an- 

 nuals and perennials thanks to the 

 cool, moist start to the growing sea- 

 son and rainy, overcast weather late 

 in the season. An interesting case 

 of CALCIUM DEFICIENCY was identified 

 on oriental lily The outer third of 

 several of the youngest leaves were 

 distorted and began to turn black 

 Botrytis was initially identified as 

 the causal agent, but turned out to 

 be a secondary problem following a 

 calcium deficiency. 



Turf 



FuNGAL LEAF SPOTS and red thread 

 were fairly common during the 



eady- and mid- summer period, but 

 were not a severe problem due to 

 the relative lack of moisture The 

 typical summer diseases such as 

 BROWN patch, pythium, and summer 

 PATCH occurred sporadically, but dis- 

 ease pressure was generally light be- 

 cause of the cooler, drier conditions. 

 The only real 'spurt' of these typical 

 summer diseases was during early- to 

 mid-luly, when we had an outbreak of 

 PYTHIUM BLIGHT and a couple of cases 

 of SUMMER PATCH On home lawns 



As the summer progressed, it 

 seemed that anthracnose foliar 

 BLIGHT and BASAL ROT (ABR) were the 

 most common problems on blue- 

 grass, particularly in golf course set- 

 tings. Most of the ABR infections first 

 appear as small, slightly chlorotic 

 spots one inch or less in diameter 

 The turf eventually turns to orange- 

 brown then becomes bleached-out. 

 Unlike foliar anthracnose, basal an- 

 thracnose is difficult to identify with a 

 hand lens and usually requires labo- 

 ratory confirmation. 



During the next couple of months 

 we can expect to see the typical 

 problems in greenhouse crops (root 

 ROTS, Botrytis blight and canker, 

 and INSV) Remember that sanitation 

 and good air circulation are the best 

 measures for preventing diseases in 

 greenhouse crops. Also remember 

 that late autumn is the key time for 

 fungicide control of SNOW mold on 

 turf. And, the turf should continue to 

 be mown until growth ceases. 



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, C/O Dr. 

 Cheryl Smith, Plant Biology Department, 

 241 Spaulding Hall - UNH, Durham, 

 NH 03824. Samples should be accompa- 

 nied by an identification form {available 

 from your county Cooperative Extension 

 office or by calling 862-3200). Cheryl 

 Smith is the UNH Cooperative Extension 

 Specialist in Plant Health, and can be 

 reached at 603-862-3841, e-mail. 

 cheryl.smith@unh.edu. 



OCTOBER «. NOVEMBER 1997 



27 



