پراکنش فضایی و نمونه‌برداری دنباله‌ای با دقت ثابت در دو گونه کفشدوزک شکارگر Hippodamia variegata و Coccinella septempunctata در مزرعه یونجه شهرستان بروجرد

نوع مقاله : مقاله پژوهشی

نویسندگان

• ایمان صبوری ¹
• آرش راسخ ²
• امیر محسنی امین ³

¹ گروه گیاه پزشکی، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، اهواز.ایران

² گروه گیاه پزشکی، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، اهواز . ایران

³ بخش تحقیقات گیاه‌پزشکی، موسسه تحقیقات گیاهپزشکی کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران

چکیده

کلیدواژه‌ها

• مدل گرین
• کفشدوزک‌های شکارگر
• تور حشره‌گیری
• تایلور
• ایوائو

عنوان مقاله [English]

Spatial distribution and Fixed Precision Sequential Sampling Plan of Hippodamia variegata and Coccinella septempunctata population in alfalfa field of Borujerd County

نویسندگان [English]

• Iman Sabouri ¹
• Arash Rasekh ²
• Amir Mohseni Amin ³

کلیدواژه‌ها [English]

• Green’s fixed precision sequential sampling
• predator's ladybug
• sweep net
• Taylor's power law
• Iwaoís patchiness regression method

Extended Abstract

Introduction

    Alfalfa Medicago sativa L (Fabaceae) is one of the most important fodder plants with a high-quality widely grown throughout the world. The ecosystem of this perennial flowering plant includes a wide range of arthropod species. Among the natural enemies of aphids, as the most common pest of alfalfa, various species of ladybirds play an important role in establishing balance and natural regulation of the pests. As polyphagous biological control agents, Hippodamia variegata (Goeze) and Coccinella septempunctata L. (Col.: Coccinellidae) ladybirds consume many aphid species as well as weevil larvae, in alfalfa fields. Particularly in the case of sequential sampling, knowing the kind of spatial distribution of an arthropod population facilitates the precise, dependable, and cost-effective sampling of that population. Sequential sampling is a method that expresses the appropriate location of populations based on the average population density. Sequential sampling provides a quick and reliable estimate of populations by reducing the number of samples, and the time required for sampling and increasing the accuracy, relative to conventional methods of estimating.

Materials and Methods

Sampling of the intended predator population was performed on a weekly sampling program during two cropping seasons of 2021 and 2022 in a seven-hectare alfalfa field, Hamdani cultivar located in Borujerd County (Lorestan Province), using an insect net (opening diameter 30 cm, handle length 110 cm and net length 45 cm). The samplings were conducted from the middle of March to the end of September for both cropping seasons. Using the collected data, the mean and variance of the whole insect population were determined. Taylor's power law (TPL) and Iwao's patchiness regression approach were used to establish the geographical distribution of the predators' whole insect populations. Using Green's fixed-precision sequential sampling plan, the number of necessary samples, and the equations of decision lines were calculated to estimate their population average.

Results and discussion

In this research, to determine the type of distribution pattern of two species of predatory ladybirds, H. variegata and C. septempunctata, Taylor's power law, and Iwao's patchiness regression methods were used. The coefficient of Taylor's power law (b _H.variegata  = 1.399,  b _{C.septempunctata} = 1.563) and Iwao's (β _{H. variegata}= 1.293, β _{C.septempunctata =} 1.327) showed a significant difference with the number one. Both methods indicated aggregated spatial distribution of both species. Based on R² and F values ​​obtained from the regression calculations, the spatial distribution data of both species was a better fit with the Taylor's Power Law model (R² _{H. variegata} = 0.94, R² _{C. septempunctata} = 0.88) provided that the Iwao's model (R² _{H. variegata} = 0.86, R² _{C. septempunctata} = 0.74). Due to the significance of the distribution coefficients of the data of two years, the data of the second year were used to design the sequential sampling model. To estimate the average population of the aforementioned ladybirds, Green's fixed-precision sequential sampling plan (at three fixed precision levels, including 0.1, 0.15, and 0.25), was employed to determine the number of necessary samples and the equations of decision lines. To achieve a precision of 0.25, which is acceptable for IPM programs, the average number of samples required for C. septempunctata and H. variegata species were 7 and 8 sample units, respectively. At the precision level of 0.25, the number of samples needed for cutting the decision lines of the population of ladybird C. septempunctata was from 147 at a density of 0.03 to 46 at a density of 0.5. The number of samples needed to estimate the population of H. variegata was from 303 at a density of 0.03 to 61 numbers at a density of 0.5. Fixed Precision Sequential Sampling Plan is more economical due to cost (reduction of the number of samples) compared to conventional methods of estimating, and it provides a faster and more accurate estimate of the insect population.

Conclusion

In this research, the type of distribution pattern of two species of predatory ladybirds, H. variegata and C. septempunctata was determined for the first time at alfalfa fields in the Borujerd region of Lorestan Province. Given that one of the fundamental and advised IMP program principles is reducing management costs, the Fixed Precision Sequential Sampling Plan can be very helpful in population forecasting because it significantly reduces the number of samples and also determines the accuracy level.