الگوی پراکنش فضایی مراحل مختلف زیستی سنک عناب monosteira alticarinata (hemiptera: tingidae) در شهرستان بیرجند

عناب، ziziphus jujuba mill. گیاه دارویی شناخته شده با ارزش غذایی و خواص دارویی مختلف است که بیش ترین سطح زیر کشت آن در ایران به استان خراسان جنوبی اختصاص دارد. سنک عنابmonosteira alticarinata ghauri (hemiptera: tingidae) پس از مگس عناب carpomyia vesuviana costa (diptera: tephritidae) از مهم ترین آفات درختان عناب در استان خراسان جنوبی است. حشرات کامل و پوره ها از شیره ی گیاهی در سطح زیری برگ های میزبان تغذیه می کنند و باعث ایجاد نقاط رنگ پریده در سطح رویی برگ ها می شوند. درختان آلوده دچار خزان زودرس شده و کمیت و کیفیت محصول آن ها به شدت کاهش می یابد. به منظور بررسی الگوی پراکنش فضایی مراحل مختلف زندگی این آفت، نمونه برداری های هفتگی و منظم از درختان عناب در سال 1399 انجام شد. برگ عناب به عنوان واحد نمونه برداری انتخاب و اندازه ی مناسب نمونه با حداکثر خطای 20 %، معادل 50 واحد نمونه برداری تعیین و تراکم جمعیت تخم، پوره و حشره ی کامل در سه ارتفاع مختلف درختان عناب (1/5، 2 و 3 متر) شمارش شد. الگوی پراکنش فضایی مراحل مختلف زندگی سنک با استفاده از روش های نسبت واریانس به میانگین، شاخص میانگین ازدحام لوید، روش های رگرسیونی تیلور و آیوائو تعیین شد. پراکنش فضایی مراحل مختلف زندگی سنک عناب در سه ارتفاع درختان عناب مورد بررسی با استفاده از روش های یاد شده، از نوع تجمعی به دست آمد. آگاهی از نحوه ی پراکنش m. alticarinata موجب درک بهتر رابطه ی حشره و زیستگاه آن شده و می تواند اطلاعاتی برای تفسیر جابجایی های مکانی، مدل های رشد جمعیت و مهم تر از همه مدیریت و کنترل آفت فراهم آورد.

spatial distribution of different life stages of monosteira alticarinata (hemiptera: tingidae) in birjand region

introductionthe jujube, ziziphus jujuba mill. is a well-known medicinal plant with various nutritional values and pharmacological properties which grows in south khorasan province, iran, as the major producer of jujube in iran. the jujube lace bug, monosteira alticarinata ghauri (hemiptera: tingidae) is the second most important pest of jujube trees after the jujube fruit fly, carpomyia vesuviana costa (diptera: tephritidae) in south khorasan province. its occurrence in iran was reported for the first time in 2012 by moodi from birjand in south khorasan province. adults of m. alticarinata overwinter on the bark of trees, under fallen leaves and in spring they move to young jujube leaves where they feed and lay eggs on the underside, thus starting infestations. both m. alticarinata adults and nymphs feed on underside of leaves and produce small chlorotic stippling on the upper leaf surface. leaf undersides appear specifically black varnish spotted due to lace bug excrement. their injury reduces photosynthesis and respiration and also causes aesthetically displeasing injured leaves. as a result, foliage becomes bronzed and leaves may drop early. the accumulation of excrements on the leaves, also results in reduction of the gas exchange like other lace bugs. distribution pattern of an insect population is an important aspect as it represents the interaction between individuals of the species and their habitat. the importance of spatial distribution comes from its central role in ecological theories and its practical role in population sampling theory as well as in the development of rational pest management strategies. for these reasons, a great deal of effort has been invested in characterizing the spatial distribution of insect populations. spatial dispersion of a population usually follows one of three models: aggregated (or contagious), random (or by chance) or uniform (or regular). to determine the spatial distribution pattern of a given species it is necessary to obtain data on the count of individuals in the ecosystem to be considered. despite the importance of m. alticarinata in the region, no study has been conducted on the distribution of this pest in jujube plant in iran. knowledge of spatial distribution of m. alticarinata is useful for designing, pest management and development of population models and assessment of levels of its damage. materials and methodsto investigate the spatial distribution pattern of different life stages of m. alticarinata, samplings were done weekly of jujube trees in 2020. jujube leaf was selected as sampling unit and the reliable sample size with maximum relative variation of 20% was obtained 50. the number of egg, nymph and adult was recorded in three heights of jujube trees (1.5, 2, and 3 meters). the spatial distribution pattern of different life stages of lace bug was determined using mean-variance ratio, lloyd’s mean crowding index, taylor´s power low and iwao´s patchiness regression model. results and discussionspatial distribution of an insect is affected by various environmental factors such as food, temperature, light, habitat condition, and other biotic and abiotic factors. the results of the study indicated an aggregated pattern for the spatial distribution of m. alticarinata in almost all heights of jujube. in other words, different heights of jujube did not have any marked effect on the distribution pattern of this pest. information on spatial distribution of m. alticarinata can be used in estimating the number of samples required from an area to reliably estimate pest infestation levels to develop effective management programs. similar to our results, the change in plant height did not affect the spatial distribution pattern of agonoscena pistaciae and diaphorina citri nymphs and in both cases the pattern of distribution was reported to be aggregated.