DIAGNOSTIC UPDATE 



£3 



We have certainly had our 

 share of •bizaiie' weather this 

 spring! I'm holding out hope for 

 June to be more typical" and not 

 like last year (with only six days 

 above 80 degreesl. 



The cloudy, cool weather was a 

 major contributor to an increase in 

 BOTRYns problems on greenhouse 

 crops, particulariy bedding plants. 

 Root rots caused by pythium have 

 also been fairiy common on pansy, 

 impatiens. and geranium. The lack 

 of sunlight decreases the rate of 

 transpiration and. as a result, the 

 amount of water required by the 

 plant is also reduced. If watering is 

 not reduced accordingly, the wet 

 growing media can favor the devel- 

 opment of the root rot. .\nother 

 problem favored by these low-light 

 conditions is edema, a disorder 

 common on ivy geraniums. Many 

 geranium growers throughout New 

 England have also reported symp- 

 toms resembling nutrient imbal- 

 ances. Most of the samples that 

 were submitted to the UNH-PDL 

 were diagnosed with high soluble 

 salts damage or iron-manganese 

 toxicity. Symptoms of soluble salts 

 injury include necrosis (browning) 

 of die leaf margins, interveinal chlo- 

 rosis or yellow/brown speckling, and 

 upward cupping of leaf margins. 

 Iron-manganese toxicit>' symptoms 

 are similar to those caused by high 

 soluble salts, except the interveinal 

 chlorosis and browning are usually 

 more severe. Iron-manganese toxic- 

 ity is common with poor drainage 

 and/or low pH. The cold weather 

 also caused problems on dianthus 

 and tomatoes. The leaves devel- 

 oped a purple pigmentation (actu- 

 ally due to a phosphorus dencienc\ 

 caused by cold soil temperatures i 

 Additional problems diagnosed on 

 greenhouse crops included phyto- 

 PHTHORA root rot on fuchsia, ixsv on 

 amarylis. and bacterial bught on 

 German iv>'. 



T^TC DiEBACK due to winter in- 



jury drought stress is beginning to 

 show up on a wide range of woody 

 species. Remember, we can expea 

 to see symptoms of the '95 drought 

 for another year or two. Besides 

 twig dieback (due to natural prun- 

 ing' or increased susceptibility to 

 fungal infections), needle loss on 

 conifers (particularly on the upper 

 branches of spruce) is also a com- 

 mon symptom of drought-induced 

 injur>'. Some areas in southern New 

 Hampshire experienced a four-to- 

 six week drought last summer. This 

 will compound the effects of the 

 pervious droughtis). The wet fall 

 may also have delayed dormanc\- in 

 some species, thus increasing the 

 chance for winter injurv. Prune any 

 branches that did not break bud by 

 the end of .May. Most of the prob- 

 lems diagnosed on woody orna- 

 mental during March and April were 

 due to winter desiccation. 



Turfgrass infected with either (or 

 both) of the snow mold fungi be- 

 gan aTTi>ing in the PDL in April. Al- 

 though we did not have prolonged 

 snow cover in the southern part of 

 the state, we did have plenty of 

 moisture. F*ink snow mold does 

 quite well under these conditions 

 and can continue to be a problem 

 as long as the conditions remain 

 moist and cool. 



During the eariy summer months 

 problems on turfgrass include 



BROWN P.^VTCH and PYTHIUM BLIGHT 



(both common during periods of 

 warm, humid weather with rainy 

 periods), and leaf spots Red 

 THREADS has been fairly common 

 on both perennial ryegrass and 

 fescues. 



Several diseases cause problems 

 every year on annuals and p>erenni- 

 als. BoTRYns bught is probably the 

 most common. The disease is fa- 

 vored by high humidity' and pro- 

 longed leaf wetness, so any mea- 

 sures to increase air flow and re- 

 duce the duration of leaf wetness 

 will go a long way in reducing the 



impact of this disease, leaf spots 

 caused by a multitude of fungi and 

 seve.ral bacteria are also common 

 on herbaceous plants Wet condi- 

 tions favor their development and 

 spread. One other problem is com- 

 mon on this group of plants during 

 the growing season. Clusters of circu- 

 lar, brown spots often seen on the 

 upper or youngest leaves are usu- 

 ally caused by pl\.nt bug feeding. A 

 small dark spot or puncture wound 

 can been seen in the center of 

 each spot upon close inspection 

 with a hand lens. 



Shoot bught (Monilinia) can cause 

 significant damage to PruHus sp. 

 Fungicides should be applied dur- 

 ing bloom, and infected twigs 

 should be removed during dry 

 weather Primary apple scab lesions 

 should be evident on Ma/us sp. by 

 early lune. Secondar>' scab infec- 

 tions should be controlled with fun- 

 gicides to reduce the likelihood of 

 early defoliation on susceptible 

 crabapple cultivars. Bacterial 

 blight on lilac and forsythia occurs 

 every year. A combination of prun- 

 ing and copper fungicides usually 

 provide effective control. Be sure to 

 prune during dr>' weather and dis- 

 infect the pruning tool between 

 each cut 



Remember, sanitation and wa- 

 tering practices that avoid pro- 

 longing the duration of leaf wet- 

 ness are the most important cul- 

 tural methods for preventing dis- 

 ease problems. 



If you visk tc submit plant material to 

 the PDL lor diagnosis, send samples 

 Witk a check for 512.00) to-. The UNH 

 Plant Diagnostic Lab. CO Dr. Cheryl 

 Smith. Plant Biology Department, 

 Spaulding HaH-UNH. Durham. NH 

 03824 Sampks should be accompanied 

 by an identification form {available from 

 your county Cooperative Extension). 

 Cheryl Smith is the U.NH Cooperative 

 Extension Specialist in Plant Health, and 

 can be reached at (603 1 862-3200. 



THE PLANTSMAN 



