Spatial dispersion and optimum sample size for Bird cherry-oat aphid, Rhopalosiphum padi (Hemiptera, Aphididae) on corn

Amir-Maafi, Masood; Ebrahimi, Laleh

doi:10.48311/jcp.2026.117868.82884

Spatial dispersion and optimum sample size for Bird cherry-oat aphid, Rhopalosiphum padi (Hemiptera, Aphididae) on corn

Document Type : Original Article

Authors

Masood Amir-Maafi ¹

Laleh Ebrahimi ²

¹ Sunn Pest Research Department, Iranian Research Institute of Plant Protection (IRIPP), AREEO, Tehran, Iran.

² Biological Control Research Department, Iranian Research Institute of Plant Protection (IRIPP), AREEO, Tehran, Iran.

10.48311/jcp.2026.117868.82884

Abstract

The bird cherry-oat aphid, Rhopalosiphum padi L. (Hemiptera: Aphididae), is one of the most important biotic constraints for corn production. Significant yield loss can occur without pest monitoring and timely management. Understanding the spatial distribution of R. padi is critical to developing a reliable sampling plan. This study aims to characterize the spatial distribution of aphids in corn fields in Karaj (Alborz province, Iran). Field sampling of R. padi populations (nymphs and adults) on corn in Karaj in September 2022 produced a dataset of 20 estimates of mean aphid density (m; number of aphids per plant) and variance (s²). To determine its distribution and inform population density sampling, we investigated the spatial distribution of R. padi using Taylor’s power law and Iwao’s mean crowding. Both methods indicated an aggregated distribution, as the aggregation parameter (b = 1.379) and density contagiousness coefficient (β = 3.577) exceeded 1. We then estimated the optimal sample size (n) at 0.10 and 0.25 precision levels using both models. Optimal sample size decreased with decreased precision and mean aphid density, varying significantly with both the precision level and regression model. At a 25% precision level, the required sample size ranged from 56 to 516 plants (Taylor’s) and from 59 to 802 plants (Iwao’s). When precision is increased to 10%, the required sample sizes become 334–3,227 plants (Taylor’s method) and 371–5,013 plants (Iwao’s method). These data on spatial distribution and optimal sample size are crucial for monitoring and managing R. padi effectively.

Keywords

Rhopalosiphum padi, Taylor’s power law, Iwao’s mean crowding, optimum sample size

Subjects