Comparative study of performance and resistance of ten poplar clones against two key pests Paranthrene tabaniformis and Cerura vinula in north Khorasan province.

To study performance as well as susceptibility and resistance of selected poplar clones against two key pests، ten clones were planted in a randomized complete block design with three replications in 2004 to 2007. Nine out of 25 trees in the middle of each plot were selected. Field sampling was conducted at the end of growing season of diameter and height and the pest''s damages as well. Recorded data were analyzed using SAS software and the means compared with Duncan''s test. Analysis of variance conducted on obtained data of diameter and height revealed a significant difference between the clones. Among the poplar clones، the comparison of means showed that P. nigra 62. 127، P. deltoides 69. 55، P. nigra 63. 135 and P. nigra 62. 154 had the highest height and diameterwhile P. alba was the lowest one. Analysis of variance conducted on obtained data of damage by Paranthrene tabaniformis and Cerura vinula indicated significant difference between the clones. Mean infestation of Paranthrene tabaniformis were highest on clones of P. nigra dartoom (native)، P. nigra 62. 127، P. x. euramricana 455 and P. x. euramericana 561. 41 (in a single group). The lowest damage was observed on p. alba beshghardash. The highest damage level of C. Vinulawas observed on clone P. x. euramericana 561. 41 while the lowest damage were seen on P. deltuides 69. 55and P. alba beshghardash There was no damage on P. alba 44. e�Y mi
����sis were also done for all phases. Comparison of the treatment means using Duncan test showed that there was significant differences (P<0. 01) in number of seeds per pod produced by the treatments، Gharayonje variety with 6. 183 and variety of Kouzareh with 4. 379 had the most and least average of seeds per pod، respectivly. The significant differences were also observed in undamaged seeds، sampling times and interaction، as variety of Kefandoa with 91. 46% and variety of Rahnani with 79. 45% had the most and less of undamaged seeds respectivly. In comparison of sampling times، there were also significant differences in seed damage between sampling time. The least damage (2. 90%) was observed in the seeds harvested in first sampling (mid-August)، however the highest percentage damage (20. 37%) caused by the pest occurred in third sampling (early September). The results showed that in the early September، the wasp activity reaches its peak. Therefore it can be concluded that mid-August is the best harvesting time to reduce the pest damage to the seed crops.