تغييرات ساليانه جمعيتي لاروهاي پروانه جوانه خوار بلوط (Tortrix viridana L) روي دو گونه بلوط دارومازو (ًQuercus infectoria Oliv) و ويول (Q. libani Lindl) در استان آذرباجان غربي

Annual Populational Dynamism of Oak Leaf Roller (Tortrix viridana L.) Larvae on Quercus infectoria Oliv. and Q. libani Lindl. in West-Azerbaijan Province

يكي از عوامل اصلي تخريب جنگل هاي بلوط، جوانه خوار بلوط .Tortrix viridana L است و خسارت زيادي را به اين جنگل ها وارد مي سازد. هدف اصلي از انجام اين تحقيق، بررسي تغييرات جمعيتي اين آفت طي دو سال مختلف و عوامل تاثيرگذار بر آن به منظور تعيين راهكار هاي مناسب كنترل آفت بود. اين تحقيق طي سال هاي ۹۳ و ۹۴ در منطقه قبرحسين با مساحتي در حدود ۲۵۰ هكتار انجام شد و در چهار جهت جغرافيايي اصلي (شمال، شرق، جنوب و غربي)، ترانسكت هايي با فواصل ۱۰۰ متري پياده شد. در مجموع، در هر جهت تعداد ۳۰ درخت دارمازو Quercus infectoria و تعداد ۳۰ درخت وي ول Q. libani كه از لحاظ شكل ظاهري مشابه بودند (جهت كاهش خطاي نمونه برداري) در هر چهار جهت جغرافيايي اصلي مورد اندازه گيري قرار گرفتند. در هر درخت نيز چهار شاخه انتخاب (هر جهت يك شاخه به طول ۵۰ سانتي متر) و در هر شاخه از نوك شاخه به سمت داخل، لاروهاي آفت شمارش گرديد. در هر دو سال، تعداد لاروهاي جوانه خوار بلوط روي دارمازو بيشتر از وي ول بود. تعداد لاروهاي جوانه خوار بلوط در هر دو گونه بلوط دارمازو و وي ول در سال ۹۴ نسبت به سال قبل افزايش چشم گيري داشته است كه ممكن است با افزايش دما مرتبط باشد. بررسي فراواني جمعيت لاروهاي جوانه خوار بلوط در جهت هاي جغرافيايي نشان داد براي هر دو گونه دارمازو و وي ول در سال ۹۳ بيشترين و كمترين تعداد لارو به ترتيب در جهت جغرافيايي شرقي و غربي و در سال ۹۴ نيز بيشترين و كمترين ميزان فراواني لاروها به ترتيب در جهت جغرافيايي جنوبي و شمالي بود.

Introduction: Various pests attack oak trees and in most cases heavily damage them. The European oak leaf roller is one of the important oak herbivore in some regions of Iran including Zagros oak forests, especially in Kohkiluyeh and Boyer Ahmad, Lorestan, ChaharMahal and Bakhtiari, Fars, and West Azarbaijan Provinces, and also, critical pest of oak forests in some European and North African countries, as well as in Iraq . Repeated removal of oak leaves, particularly by herbivores such as Tortrix viridana in spring, reduces stored photosynthates in oak trees leading to their decreased diametrical growth. Materials and Methods: The Ghabre-Hossein region (Piranshahr) was selected as the field operations region because it is one of the most important infestation centers of the European oak leaf roller in the oak forests of West Azerbaijan. The research was carried out in two consecutive years. Samples of larval instars were taken in early May. Since the sample plot in sampling methods can be pointed or lined (transects), the four cardinal directions were selected in this study and transects at I 00 m intervals were located in each direction. To reduce sampling error, Aleppo (Quercus infectoria) and Lebanon (Q. libani) oak trees were selected for measurements that were similar in appearance and almost uniform with crowns or trunks aligned along the transects. In each studied tree, four suitable branches were selected (one in each cardinal direction), and the number of larvae from the tip of each branch to a length of 50 em inwards was counted and recorded in forms prepared beforehand. The larvae were counted in mid-May when all larvae were in their last (fifth) instar. In all, 30 Aleppo and 30 Lebanon oak trees were selected in each cardinal direction, and four branches in each direction of these trees were measured. The survey method was used by employing a 25 m rope, a slope gauge, and a compass to locate the sampling transects. 2x4 factorial split - plot in time design were used as the statistical method for assessing the effects of various cardinal directions and of oak species on abundance of the European oak leaf roller. If significant differences between the means was detected, Tukey's HSD test was employed (IBM SPSS, 18). Results and Discussion: This pest has a single annual generation and five larval instars. It overwinters, and spends the entire summer, autumn, and winter, as egg. Eggs hatch in late March. Larvae pierce buds to enter into and feed inside them, and large larvae can leave buds and start feeding on other buds. The results showed that in both years the number of leaf-roller moth larvae were more on Q. infectoria in comparison to Lebanon oaks and it seems that oak species (Q. infectoria) is more preferable for the pest (Tortrix viridana) to feed upon than Lebanon oaks. The study of population changes of the oak leaf-roller moth in the geographical directions in 2014 proved that in both of the tree species the maximum and the minimum number of larvae were in the east and the west directions, respectively. In 2015, it also became clear that the highest and the lowest frequency of the larvae were in the south and the north, respectively. The results confirmed the influence of wind direction on distribution orientation of leaf-roller moth larvae. The number of oak leaf-roller moth larvae significantly increased in 2015 in comparison to the previous year which can be due to the temperature increase in this year. Conclusions: The number of larvae of the European oak leaf roller on Aleppo oak trees was higher compared to Lebanon oak trees in both 2014 and2015, which shows this pest prefers Aleppo oak trees over Lebanon oak trees. The number of larvae on both oak species in 2015 was considerably higher compared to the previous year, which may have been caused by increased temperatures in 2015. Study of population changes of the pest in the cardinal directions indicated that the maximum and minimum number of larvae on both oak species in 2014 were observed in the eastern and western cardinal directions, respectively, and the maximum larva abundance occurred in the eastern direction of tree crowns. The dominant wind in the region blew ti·01n the southwest, and seemed to be the main reason why larvae's abundance and distribution occurred in the eastern direction (that was not influenced by wind currents). In 2015, the maximum and minimum abundance of larvae were also observed in the southern and n01ihern cardinal directions, respectively. Moreover, the maximum larva abundance occurred in the northern direction of tree crowns, with the dominant wind in the region blowing in the northeast direction, which demonstrated the direct influence of wind on the orientation and distribution of the European oak leaf roller population. Results obtained in 2014 and 2015 showed that orientation and distribution of the European oak leaf roller can be influenced by wind direction and temperature.