FORUM 



quent problem diagnosed on 

 greenhouse crops and the best 

 methods of control are sanitation 

 and preventative fungicide 

 drenches. Tomato spotted wilt 

 virus (TSWV) is a serious disease 

 which is showing up more and 

 more frequently throughout the 

 state. The virus, transmitted by 

 thrips, has an extremely wide hit 

 range. The PDDL is not equipped 

 to run the diagnostic tests neces- 

 sary to diagnose TSWV, so the 

 samples are sent to an outside lab 

 for confirmation. A plant infected 

 with TSWV cannot be cured. In- 

 fected plants should be destroyed 

 (they should not be sold!) to pre- 

 vent the spread of the virus. The 

 primary means of controlling 

 TSWV is through careful inspec- 

 tion of all incoming plant mate- 

 rial and chemical control of the 

 thrips. The most consistent prob- 

 lems on woody ornamentals have 

 been anthracnose and leaf spots 

 on deciduous trees and shrubs; 

 needlecasts (particularly 

 Rhizospheara on blue spruce) and 

 tip blights on evergreens; winter 

 injury, leaf spots, Phytophthora 

 root rot on broad leafed ever- 

 greens (rhododendrons); and 

 wood decay following mechanical 

 injury. Sanitation is a major fac- 

 tor in the management of these 

 diseases. Cultural measures such 

 as pruning diseased branches and 

 shoots, raking and removing 

 fallen leaves and needles, proper 



fertilization, thinning to promote 

 air circulation, and providing ad- 

 equate water can usually provide 

 adequate control of many diseases 

 of wood ornaments. However, 

 fungicide applications may be 

 necessary, particularly for tip 

 blights and needlecasts of ever- 

 greens. On annual and bedding 

 plants, the two major diseases, 

 leaf spots and Botrytis blight, can 

 be managed with a combination 

 of fungicides and cultural prac- 

 tices. The variety of fruits and 

 vegetables grown in New Hamp- 

 shire results in a wide range of 

 diseases diagnosed. In general, 

 fungal fruit rots, leaf spots, and 

 blights account for the majority 

 of the diseases diagnosed on these 

 crops by the PDDL each year. As 

 with all crops mentioned previ- 

 ously, control is best achieved 

 with strict sanitation measures 

 and other cultural practices com- 

 bined with fungicide and 

 baceteriacide applications where 

 necessary. 



The proper diagnosis of disease 

 problems depends strongly on the 

 quality and condition of the 

 sample received by the PDDL. 

 Completely dead or dry plant ma- 

 terial is of no value for diagnosis. 

 The sample should be fresh, taken 

 just prior to delivery or mailing. 

 Be sure to include generous 

 amounts of plant material (one or 

 two leaves is not sufficient). Ide- 

 ally the sample should include a 



progression of symptoms. The 

 sample can be brought to your 

 county Cooperative Extension Of- 

 fice or the PDDL, or mailed. 

 When mailing samples, place the 

 sample in a sturdy box or padded 

 postal envelope and mail them 

 early in the week (so the sample 

 does not sit in the post office 

 over the weekend). Be sure to in- 

 clude a full description of the 

 problem, including a history of 

 chemical and fertilizer use. 

 During the next year the decision 

 will be made to either expand the 

 PDDL into a Plant Pest Diagnos- 

 tic Clinic staffed by a full-time 

 plant protection specialist, or dis- 

 continue the diagnostic services 

 presently provided. The services 

 offered by the expanded Clinic 

 would include insect identifica- 

 tion and diagnosis of stress-related 

 problems in addition to those 

 presently offered. Another goal of 

 the expanded Clinic would be to 

 broaden the educational outreach 

 program through talks to garden- 

 ing clubs and other groups, and 

 various types of publications. 

 This decision will most likely be 

 based on feedback form county 

 agents, extension specialists, and 

 growers, as well as future budget 

 constraints. 



Cheryl Smith is Plant Disease Diagnosti- 

 dan at the UNH Piant Biology Depart- 

 ment Diagnostic Lab, Nesmith Hall, 

 Durham. For information, contact Cheryl 

 at 862-3841. ^ 



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