AGNOSTIC UPDATE 



Well, it looks like the drought is 

 officially over (just in case you 

 didn't notice the rain we've had 

 lately)! Be sure to keep in mind, 

 however, that the effects of the 

 drought of 1995 will be seen during 

 the next few growing seasons (see 

 the Oct/Nov issue for a discussion of 

 possible effects due to drought stress). 

 Samples showing symptoms of drought 

 stress continued to be submitted to 

 the PDL during September and early 

 October. The number of samples re- 

 ceived during the last two months 

 was significantly less than the same 

 time period last year and may be 

 the result of lower disease incidence 

 due to the lack of moisture that fa- 

 vors fungal and bacterial diseases. 



Drought-related twig dieback was 

 diagnosed on maple, balsam and fraser 

 fir, and dogwood. The dogwood was 

 also infected with the canker-causing 

 fungus cytospora. We will be seeing 

 a greater incidence of dieback and 

 cankers caused by 'weak' fungal patho- 

 gens next year. Fungi such as pho- 

 mopsis and botryosphaeria are op- 

 portunistic fungi that infect weakened 

 and stressed tissues Needle blight 

 {Hormonema merioides) was diag- 

 nosed on balsam fir. This fungal dis- 

 ease is common under conditions of 

 high humidity and is also more com- 

 mon on stressed plants. Several red 

 pine stands around the state, par- 

 ticularly those on light, sandy soils 

 have been showing high levels of 

 mortality. Site visits and culturing 



have not yielded any pathogens. Ex- 

 tension pathologists and entomolo- 

 gists I've spoken with in neighboring 

 states have also noted the red pine 

 decline. It appears the trees have 

 been weakened by drought stress 

 over the last few years and then suc- 

 cumbed to attack by bark beetles. 



We didn't get the rains until after 

 the temperatures cooled off, so turf 

 diseases such as Pythium blight and 

 brown patch were not much of a late- 

 season problem Powdery mildew 

 was prevalent on the usual hosts (li- 

 lac, phlox, azalea, rose, turf, cucurb- 

 its...), but didn't seem to be any 

 more of a problem compared to past 

 years. 1 haven't received any samples 

 of powdery mildew on poinsettia 

 from this year's crop. An E-mail no- 

 tice was received this morning (Nov. 

 9) however, from the regulatory folks 

 in Maine. Powdery mildew was found 

 in one greenhouse on the poinsettia 

 cultivar Freedom Red. If you are 

 growing this cultivar, be sure to care- 

 fully scout the plants for fungal colo- 

 nies. 



What should we watch out for over 

 the next few months? Based on 

 records form previous years, the big- 

 gest problems have been botrytis 

 blight, oedema, root rots, and INSV. 

 Botrytis blight is always a threat, par- 

 ticularly under conditions of high 

 relative humidity and cool night tem- 

 peratures. Most crops are suscep- 

 tible, particularly when in flower. Be 

 sure to space plants to allow for 



good air circulation, vent when the 

 humidity is greater than 90%, avoid 

 wounding, and remove senescent or 

 damaged plant material. Oedema, a 

 problem also related to high relative 

 humidity, is most common on ivy ge- 

 raniums, but occurs on other crops 

 such as zonal geraniums, peperomia, 

 and jade. Root rots occur on all green- 

 house crops. Root rots caused by 

 pythium are common in poorly drained 

 mixes, while those caused by thelavi- 

 opsis, fusarium, and rhizoctonia are 

 more common on drier mixes. Fusa- 

 rium rot or wilt is also a common 

 problem on cyclamen. The initial 

 symptoms are yellowing of the older 

 leaves followed by wilting. You can 

 check the plant for infection by 

 fusarium by cutting the corm in half 

 (cross-section). Infected corms will 

 have a brown-black discoloration of 

 the vascular system. Infected plants 

 should be destroyed and the remain- 

 der of the crop should be drenched 

 with a fungicide. 



I hope everyone has a great holi- 

 day season. Cheers! 



If you wish to submit plant material to the 

 PDL for diagnosis, send samples {with a 

 check for $12.00) to-. The UNH Plant Di- 

 agnostic Lab, C/O Dr. Cheryl Smith, Plant 

 Biology Department, Nesmith Hall - UNH, 

 Durham, NH 03824. Samples should be 

 accompanied by an identification form 

 {available from your county Cooperative Ex- 

 tension, or at the PDL). Cheryl Smith is 

 the UNH Cooperative Extension Specialist 

 in Plant Health, and can be reached at 

 (603) 862-3841. 



Route loi 

 PO Box z66, Dublin, NH 



603-563-8180 



Perennials ♦ Herbs ♦ Wildflowers 



no Varieties in 6-cell Packs 



UPS shipping Available 



Annual Bedding Plants (6-ceU packs) 



Zonal Geraniums (4 1/2" pot) 



Hardy Mums in Season 



Perennials (available in 2, 3, 4 and 6 qt. pots) 



DECEMBER 1995 -f JANUARY 1996 



