Journal of Food, Agriculture and Environment

Optimum sampling plan for the population of English grain aphid, Sitobion avenae (F.) (Hem.: Aphididae) on wheat in Iran

Author(s):

Shahram Shahrokhi ^1*,  Masoud Amirmaafi ²

Recieved Date: 2011-09-24, Accepted Date: 2012-01-06

Abstract:

Reliable and practical sampling programs are essential for the effective utilization of control tactics in integrated pest management systems. In order to estimating the English grain aphid, Sitobion avenae (F.), population in wheat fields, the optimum sample size required was studied for fixed precision levels recommended for research (0.10) and integrated pest management (0.25) purposes. Weekly counts were carried out from the end of March or early April (beginning of aphid migration) until the breakdown of the population in the field (toward the end of May) in Varamin region (near Tehran, capital of Iran) during 1999 and 2000 growing seasons. Fifty tillers were randomly chosen and all leaves were examined for the presence of Sitobion avenae individuals. Optimum number of samples was calculated using both the general formula and the formula for the negative binomial model. Results revealed that the aphid density was low at the beginning of the season, but a rapid increase in population density occurred in early and middle of April in 1999 and 2000, respectively. Population peak was observed in late April and then decreased rapidly, so that there was low number of aphid individuals per tiller in early May. Sample size curves indicated that estimating English grain aphid population density in wheat can be accomplished with relatively little sampling effort when population intensity was higher than three aphids per tiller. However, sample size increased dramatically for S. avenae when population intensity was below 0.5 aphids per tiller. The optimum number of samples decreased as population density increased. The calculated values for the optimum number of samples indicated that a precision of 10% is not practically feasible for the densities observed in the present study. However, the calculated values of the optimum number of samples at 0.25 precision level provided a basis for the sampling program, so that the precision of the estimates for the various population parameters would be at acceptable level. 

Keywords:

Sampling, sample size, population fluctuation, English grain aphid, Sitobion avenae

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Journal: Journal of Food, Agriculture and Environment
Year: 2012
Volume: 10
Issue: 1
Category: Agriculture
Pages: 401-403

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