چكيده فارسي :
لاروهاي سوسك برگخوار غلات Oulema melanopus با تغذيه از برگ پرچم گندم موجب خسارت مي گردند. اين تحقيق با هدف بررسي امكان خسارت زايي اين آفت روي گندم در سه مزرعه استان مازندران واقع در نكا (ايستگاه بايع كلا)، ساري (ايستگاه دشت ناز) و جويبار (ايستگاه پهناب) در طي سال هاي 1392 و 1393 به اجرا در آمد. در هر مزرعه 10 نقطه تعيين و همزمان با اتمام فعاليت تغذيه اي لاروها، از هر نقطه 10 ساقه ي آفت زده و 10 ساقه ي سالم به طور تصادفي انتخاب و شماره گذاري گرديدند.از برگ پرچم ساقه هاي آفت زده عكس تهيه شد و با استفاده از نرم افزار UTHSCSA ImageTool for Windows Version 3 شاخص خوردگي سطح برگ پرچم در تصوير نمونه ها در 4 رده (10٪>، 10-20، 20-40 و 40٪<) گروه بندي شدند. در فصل برداشت، خوشه ساقه هاي علامت‌گذاري شده جمع آوري و تعداد دانه و وزن دانه ي موجود در هر خوشه و وزن هزار دانه اندازه گيري گرديد. نتايج نشان داد كه فعاليت تغذيه اي لاروها مي تواند بر وزن و تعداد دانه در هر خوشه و وزن هزار دانه تاثير منفي گذاشته و با افزايش درصد خوردگي سطح برگ پرچم، وزن دانه و تعداد دانه در خوشه كاهش يافت. در رده 40٪< خوردگي برگ پرچم، كاهش وزن دانه، تعداد دانه و وزن هزاردانه در گياهان خسارت ديده در مقايسه با گياهان سالم در سال 1392 به ترتيب 58/42%، 86/25% و 76/32% و در سال 1393 به ترتيب 42/32%, 59/15% و 82/19% بود. ولي از آنجائيكه شاخص خوردگي عموماً در رده هاي كمتر از 10٪ و 10-20٪ قرار داشته و بندرت به رده بيش از 40٪ رسيد، و همچنين تعداد ساقه هاي با برگ پرچم آفت زده در واحد سطح پايين بود، خسارت زايي اين آفت در مناطق مورد آزمايش پايين تا متوسط بود.
چكيده لاتين :
Background and Objectives
Cereal leaf beetle, Oulema melanopus (L.) (Coleoptera: Chrysomelidae), is an important world-wide pest of wheat and barley. Adults and larvae feed on the upper side of leaves and chew long strips of tissue between the leaf veins especially on flag leaf, which can reduce grain yield. However, the greater damage is usually caused by feeding activity of larvae rather than adults. This paper presents the results of an investigation on the damage caused by this pest in wheat fields.
Materials and Methods
This study was carried out in three wheat (Line: N8019) fields located at Neka, Sari, and Joybar, in Mazandaran province, Iran. Occurrence and activity of the pest in the fields was monitored weekly from mid-February until mid-May during 2013 and 2014. Coinciding with the end of larval feeding-activity (early May), 10 spots were selected in each field, and 10 beetle-infested wheat stems (showing pest damage symptoms on flag leaf surface) and 10 intact stems (without damage symptoms) in each spot were randomly selected and labeled. The flag leaves of infested stems were photographed and infestation rates (% leaf surface damage) were assessed and categorized in four groups (<10%; 10-20%; 20-40%; >40%) using UTHSCSA image tool for windows version 3. At harvest time, the spikes of all labeled stems (infested and intact) were separately collected and grain weight and grain number per spike as well as 1000-kernel weight was measured. The relationship between percentage of flag leaf damage and yield (grain number and grain weight per spike) and 1000-kernel weight was calculated using regression analysis.
Results
Overwintered adult beetles were observed in the fields from early March, with a peak activity occurring at mid-March. Larval feeding activity started during late March and continued until early May. In both sampling years, the highest grain weight loss and number of grains per spike, and 1000-weight loss were observed in the >40% of infestation rate. Grain weight loss, number of grains reduction per spike, and 1000-kernel weight loss in the >40% infestation rate were 42.58%, 25.86% and 32.76% in 2013 and 32.42%, 15.59% and 19.82% in 2014, respectively.
Discussion
Results showed that the infestation rate of flag leaves can negatively affect grain weight per spike and 1000-kernel weight. With increasing percentage of flag leaf infestation, grain weight and grain number per spike, and yield decreased. However, in this study the infestation rates of flag leaves were mostly <10% or 10-20% and rarely reached >40% rate. During two-year sampling, only 10% out of 566 beetle-infested stems showed more than 40% leaf surface damage. In contrast, 46% and 62.3% of collected samples in 2013 and 2014, had less than 20% flag leaf surface damage. Therefore, the probability of severe damage caused by O. melanopus was low to moderate in the study sites.
