Fixed precision Sequential Sampling of Aphids on Wheat fields in Ahvaz

Document Type : Research Article

Authors

• L. Ramezani
• A. Rajapour
• N. Zandi Soohani
• F. Yarahmadi

10.22067/jpp.v29i4.35402

Abstract

Introduction: Aphids are secondary pests in cereal fields but sometimes they outbreak and cause considerable damage to wheat and barley. Integrated pest management is one of the most important strategy in insect ecology and estimating population can be used to employ the strategy. Sampling of population is the most basic outdoor activities in ecology and as time goes need to fast and reliable sampling methods be felt more. Dispersion can be quantified by the comparison of observed frequency distribution data (based on a common sample unit) with mathematical models used to describe possible spatial distributions. Knowledge about dispersion pattern of an organism is required for understanding population biology, resource exploitation and dynamics of biological control agents. Moreover determination the dispersion pattern of a species is essential for developing an effective pest management program. . The degree of aggregation can be expressed by several indices of dispersion. Taylor's power law and Iwao's patchiness regression are two main models that also depend on the relationship between the sample mean and the variance of insect numbers per sampling unit. The slope of the regression model is used as an index of aggregation. Usually, sampling of insects is from the estimatation of some population parameter for research purposes or to make a pest control decision. However, the often large, fixed sample size necessary for research may be inappropriate where frequent and rapid monitoring is required to make a control decision. In such cases the sequential sampling method may be a better alternative as it characteristically has a variable sample number and can serve to classify a population in relation to a treatment level rather than provide actual estimates of population density. Designing sampling plans based on these indicators has been reported to reduce sampling effort, cost and minimize variation of sampling precision. As there were no any information about the spatial distribution and sequential sampling program of cereal aphids in Khuzestan province, this study was undertaken to determine dispersion pattern of cereal aphids in order to develop a suitable sampling plan for these pests.
Material and Methods: In order to assess the distribution pattern and density of aphid species on wheat the mixed population of aphids was sampled during 2012-2013 at three pesticide-free wheat fields (two wheat fields in Ahvaz and one in Mollasani) in Khuzestan province, southwestern of Iran. Each field was sampled twice a week throughout the growing season from initiation of tillering to grain ripening stage. Each sample included 25 plant, which were chosen randomly and the number of aphids was counted. Tillers were collected by traveling an X-shaped procedure. Spatial distribution of different developmental stages of wheat aphids were described by calculating dispersion indices (Taylor’s and Iwao’s indices of dispersion). A sequential sampling plan was also developed using the fixed precision method of Green for estimating the density of adults, Nymphs and total population.
Result and Discussion: Analysis of spatial distribution pattern using Taylor’s power law and Iwao’s regression model showed that Taylor's power law provides a better description of the aphids spatial distribution and based on this model dispersion pattern of wheat aphids population was aggregated for nymph and the total of life stage, but was random for adult life stage. Green’s fixed precision sequential sampling plan at precision levels of 0.25 and 0.10 was designed for estimating the density of the adult, nymph and total population. The results showed that the required sample size increased dramatically with increasing levels of precision, and generally ranged from 1 to 34 and 8 to 210 tillers at the precision levels of 0.25 and 0.10 respectively, and the optimum sample size for the estimation of mean aphid density decreased approximately between 44% - 83%.

Keywords

• Ahvaz
• Aphids
• sequential sampling plan
• spatial distribution
• wheat

20.1001.1.20084749.1394.29.4.12.1

---

References

1- Afshari A. and Dastranj M. 2010. Density, Spatial Distribution and Sequential Sampling plans for Cereal Aphids Infesting Wheat Spike in Gorgan, Northern Iran. Journal of Plant Protection, 32(2): 89-102. (in Persian with English abstract)

2- Ahoonmanesh A. 1993. Wheat production policy in country and introduce the wheat original design. Report of Sunn pest Conference. Faculty of agriculture, University of Tehran.

3- Damavandian M. and Asghari M. 2008. Functional Statistics for Pest Control Management. University of Mazandaran Press.

4- Elliott N.C., and Kieckhefer R.W. 1986. Spatial distributions of cereal aphids (Homoptera: Aphididae) in winter wheat and spring oats in South Dakota. Environmental Entomology, 16: 896-901.

5- Hutchison W.D., Hogg D.B., Poswal M.A., Berberet R.C. and Cuperus G.W. 1988. Implications of the stochastic nature of Kuno's and Green's fixed-precision stop lines: sampling plans for the pea aphid (Homoptera: Aphididae) in alfalfa as an example. Journal of Economic Entomology, 81(3): 749-758.

6- Latifian M. 2005. On the base of sequential sampling methods decision for integrated wheat pests control in Lorestan. Journal of Agricultural Science and Natural resources, 5: 136-146. (in Persian with English abstract)

7- Moeen-Namini S., Sahragard A. and Amir-Maafi M. 2000. Sequential Sampling of Sunn Pest in Varamin area. 14th Iranian Plant Protection Congress, Esfahan. (in Persian with English abstract)

8- Mohiseni A., Soleymannejadian A., Rajabi G., Mossadegh M.S. and Pirhadi A. 2008. Sequential sampling of overwintered sunn pest Eurigaster integriceps (Het: Scutelleridae) in rainfed wheat fields in Borujerd. Journal of Entomological Society of Iran, 27(2): 43-59. (in Persian with English abstract)

9- Onsager J.A. 1976. The rationale of sequential sampling with emphasis on its use in pest management. United States Department of Agriculture (USDA) Technology Bulletin, 1526: 1-19.

10- Rajabi G. 2009. Insect Ecology (according to Iran conditions). Ministry of Agriculture Press.

11- Rezaea N., Mossadegh M.S. and Hodjat S.H. 2010. Evaluation of population dynamics and morphometrical differences between 3 color morphs of Sitobion avenae (Fabricius). 19th Iranian Plant Protection Congress, Tehran. (in Persian with English abstract)

12- Shahrokhi Sh. and Amir-Maafi M. 2010. Spatial distribution and sampling plan of Metopolophium dirhudum (Hemiptera: Aphididae) in wheat fields. 19th Iranian Plant Protection Congress, Tehran. (in Persian with English abstract)

13- Soltani Ghasemloo, V. and Aleosfoor M. 2013. Dispersion pattern and fixed precision sequential sampling of Sitobion avenae (Fabricus) (Hemiptera: Aphididae) in wheat fields of Badjgah (Fars province) in Iran. Journal of Entomological and Acarological Research, 45:120-128.

14- Southwood T.R.E. 2000. Ecological methods, with the particular refrence to the study of insect populations. 3rd edition . Chapman & Hall Pub. London. 524 pp.

15- Taylor L.R. 1984. Assessing and interpreting the spatial distributions of insect populations. Annual Review of Entomology, 29:321-357.

16- Tomanovic Z., Kavallieratos N.G. and Athanassiou C.G. 2008. Spatial ditribution of cereal aphids (Hemiptera: Aphididae) in Serbia. Acta Entomologica Serbica, 13(1/2):9-14.

17- Wald A. 1947. Sequential analysis. John Wiley and Sons, New York.

18- Wilson L.T., Mount C., Pickel R.C. and Zalom F.G. 1983. Presence-Absence Sequential Sampling for Cabbage Aphid and Green Peach Aphid (Homoptera: Aphididae) on Brussels Sprouts. Journal of Economic Entomologiy, 76(3) : 476-479.