محاسبه دمای پایه و بررسی روند تغییرات تعداد نسل کرم سیب(cydia pomonella) ، با استفاده از مدل درجه-روز در شهرستان چناران

جنبه‌های متعدی از تغییر اقلیم و آثار آن بر اکوسیستم ها بررسی شده است، لکن تاثیر آن بر روی آفات، خصوصاً در ایران کمتر موردتوجه قرار گرفته است. تغییر اقلیم در دهه‌های اخیر تاثیرات متعددی را بر روی جامعه گیاهی و آفات گذاشته است. کرم سیب به‌عنوان یک آفت کلیدی مانند سایر آفات کشاورزی وابستگی زیادی به دمای هوا دارد. این آفت برای کامل شدن یک نسل و طی مراحل مختلف زندگی نیاز به دریافت حدود 650 درجهروز دما دارد. به‌منظور بررسی روند تغییرات تعداد نسل کرم سیب، پس از محاسبه دمای پایه، تعداد نسل این آفت در یک دوره آماری 30 ساله (13971368) با استفاده از داده‌های هواشناسی  ایستگاه‌ گلمکان و مدل درجهروز تعیین گردید و نتایج به‌دست‌آمده با نتایج تله‌های فرمونی نصب‌شده و دیتالاگر ثبت‌کننده دما در باغ گلابی در سال 1398 مقایسه گردید. دمای پایه برای کرم سیب 4/8 درجه سلسیوس به دست آمد. این آفت در دوره 30 ساله گذشته به‌جز یک سال دارای 3 نسل کامل بوده و روند درجهروز دریافتی آن مثبت و معنادار است. در ابتدای دوره آماری زندگی آفت در ابتدای نسل سوم متوقف شده و با نزدیک شدن به اواخر دوره آماری مراحل زندگی آفت رو به تکمیل شدن پیش می‌رود.  میانگین درجهروز تجمعی دریافتی در ده سال دوم دوره نسبت به ده سال اول 143 درجه و در ده سال سوم نسبت به ده سال دوم 85 درجه افزایش داشته است. در صورت ادامه روند افزایش دما وقوع نسل چهارم  آفت نیز  دور از انتظار نخواهد بود. در این شرایط استفاده از سموم و هزینه‌ها افزایش خواهد یافت.

Calculation of the Base Temperature and Investigation of Changes in Number of Codling Moth (Cydia pomonella) Generations, with Degree-Day Model in Chenaran

Introduction: Codling moth (Cydia pomonella) is one of the most important agricultural pests which annually damages apples, pears, and walnuts orchards. Like other pests, coldling moth development depends to the air temperature. Climate changes have many impacts on the environment and pests are affected by these changes, too. Codling moth has two generations in cold regions and 4 to 5 generations in warm regions per year. The number of this pest generations and the damages which it caused in the orchards depends on the amount of received cumulative temperature during a growing season. Increasing the average daily temperature will increase the cumulative degreeday and subsequently, this can increase the number of pest generations annually. The increase in the number of pests as a result of global warming can damage the environment and food security significantly. One of the effects of climate changes on the pest can be identified with an overview of the codling moth generation and its changes over the past years.Materials and Methods: Maximum and minimum temperature data of Golmakan synoptic station (Khorasan Razavi) were used to calculate the number of codling moth generations (19892018). Average daily temperature was calculated using maximum and minimum temperatures. To estimate the degreeday, the base temperature was obtained by the growth rate method at different temperatures. In this method, the growth rate of one stage of pest life (egg laying to egg hatching) was recorded at different temperatures and the temperature in which the growth rate becomes zero was considered as the base temperature. Then, degreeday was calculated by subtracting the baseday temperature from daily mean temperature and cumulative degreeday for each year was obtained by summing degreedays biofix to harvest. The biofix date in 2019 was obtained by the pheromone traps and the first male trapped in the pear orchard near Golmakan station. Pest activity initiates at temperatures higher than the base temperature, so the biofix date for each year (1989–2018) was selected based on the mean daily temperature that reached the base temperature and then increased. Biofix in the pear orchard also occurred under these circumstances. Trend of cumulative degreeday was analyzed by MannKendall nonparametric test in the statistical period 19892018 to examine cumulative degreeday changes. Pheromone trap data in pear orchards in 2019 and previous studies show that codling moth need about 650˚C degreesday temperature to complete each generation. Consequently, the number of pest generations for each year was calculated by dividing the cumulative degreeday by 650 DD. The number of male trapped in pheromone traps from biofix to harvest and flight peaks shows the number of the codling moth generations in the area of observation. Finally, the number of codling moth generations in 2019 were compared to the number of generations of this pest in the statistical period 1989–2018.Results and Discussion: The average annual temperature in Golmakan station varied from 13.9˚C to 16.7˚C from 1989 to 2018. Considering the codling moth growth rate from laying to hatching at 8, 10, 12, 14 16, 18˚C, base temperature in which the growth rate was zero, was obtained 8.4° C. The cumulative degreeday for codling moth from biofix to harvest in the statistical period 1989–2018 was between 1780˚C in 1992 and 2456˚C in 2008. Recorded air temperature data by data logger in pear orchard showed that the pest received 2251˚C degreeday in 2019. The results of MannKendall test showed an increasing and significant trend for cumulative degreeday. After calculating the cumulative degreeday, it was determined that the codling moth had three generations in the past 30 years except one year. The mean cumulative degreeday was 2067˚C in 19891998, 2215˚C in 19992008, and 2300˚C in 20092018. This shows that the average cumulative degreeday increased by 143˚C in the first ten years and 85˚C in the second ten years. According to the results of this study, at the beginning of the statistical period, pest’s life cycle stops at the beginning of the third generation and it enters the pupal and overwintering stage. Toward the end of the statistical period, pest life cycle is going to complete and reach to the fourth generation. In 2019, pheromone traps registered 3 pike flights for codling moth in the pear orchard near the Golmakan station. Thus, in 2019, there were three generations of this pest in the area of observation. If these conditions continue, the fourth generation may be presented in the area of observation in next years.Conclusion: The results of this study showed that increasing the mean of daily temperature increases the cumulative degreeday and if the temperature continues to rise, the occurrence of fourth generation will not be unexpected in the coming years. Damage to apple, pear, and walnut orchards increases by increasing number of codling moth. Therefore it will be more difficult to control this pest. Under these conditions, using pesticides will increase in agriculture and there will be environmental problems. According to the results of this study in order to manage codling moth, it is necessary to determine the exact number of generations and the appropriate time of spraying due to the time of egg hatching in each region.