GREENHOUSE CROPS 

 Botrytis was the 'Big' disease prob- 

 lem! Good air circulation, sanitation, 

 and reducing the humidity are the 

 primary means of cultural control. 

 When fungicides are required, it is 

 important to rotate the classes of 

 chemicals used to prevent disease 

 build-up due to fungicide resistance. 

 One important disease to men- 

 tion as a potential problem in 1999 

 is bacterial blight of geraniums. 

 Losses due to this disease have been 

 relatively light for the last few years, 

 but there have been early reports 

 (from other diagnostic labs) of bac- 

 terial blight on some of the gera- 

 nium stock which represents this 

 year's spring crop. The most com- 

 mon symptom is wilting of one or 

 more leaves, even though the soil is 

 moist. Leaf spotting, although less 

 common than wilt, may occur if se- 

 verely infected plants are present 

 nearby. Leaf spot develops when the 

 bacterium is splashed from one 

 plant to another or drips from hang- 

 ing baskets onto plants below. Leaf 



spotting is usually accompanied by 

 yellowing, often in a V-shaped pat- 

 tern. The symptoms on ivy gerani- 

 ums are not as obvious as those on 

 seed and zonal types. On ivy gerani- 

 ums, the symptoms are easily con- 

 fused with edema or nutrient imbal- 

 ances. If bacterial blight is sus- 

 pected, a laboratory diagnosis is nec- 

 essary to confirm the presence of the 

 bacterium. If confirmed, strict mea- 

 sures are needed to reduce potential 

 crop loss: (i) plants cannot be cured 

 or protected by fungicide sprays or 

 drenches, (ii) infected plants should 

 be destroyed and soil should not be 

 reused, (iii) suspicious plants should 

 be isolated until a diagnosis is com- 

 pleted (cuttings should not be taken 

 from suspicious plants), and (iv) tools, 

 pots, flats, and bench tops should be 

 sanitized with a disinfeaant. 



TURF 



Snow molds should not be as much 

 of a problem as in previous years 

 because the ground was frozen prior 

 to the establishment of permanent 



snow cover (at least in the southern 

 portions of New Hampshire and 

 Maine). Remember, however, that if 

 we get a significant thaw during 

 January or February followed by ad- 

 ditional snowfall, snow molds may 

 develop to significant levels. Al- 

 though fungicides applied during 

 mid-winter thaws have some effec- 

 tiveness, they are not as effective as 

 a combination of systemic and con- 

 tact fungicides applied in the fall. 



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, CI 

 O Dr. Cheryl Smith, Plant Biology 

 Department, 241 Spaulding Hall - 

 UNH, Durham, NH OJ824. Samples 

 should be accompanied by an identi- 

 fication form (available from your 

 county Cooperative Extension office 

 or by calling 862-^200). Cheryl 

 Smith is the UNH Cooperative Ex- 

 tension Specialist in Plant Health, 

 and can be reached at 603-862-^841, 

 e-mail: cheryl. smith @unh. edu. 



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