Relationship Between Population Estimates of Cotton Fleahoppers (Hemiptera: Miridae) Obtained by Terminal and Whole Plant Examinations

Abstract

The standard method for assessing cotton fleahopper, Pseudatomoscelis seriatus (Reuter), abundance in cotton, Gossypium hirsutum L., involves direct counts of adults and nymphs on main stem terminals. Although this practice appears to provide adequate estimates for pest management programs, the accuracy and precision of population estimates obtained from terminal sampling, relative to whole plant examinations and potential time-of-day sampling effects, have not been investigated. We examined the distribution of cotton fleahopper adults and nymphs within cotton plants twice a day (0800 - 1130 h and 1300 - 1630 h) in 2007 and 2008 to determine whether the numbers of fleahoppers in the terminal of plants accurately and reliably reflect the numbers of fleahoppers on those plants. Overall, the mean numbers and distribution patterns of fleahoppers observed during the morning and afternoon sampling periods were statistically similar. Consequently, time-of-day sampling effects were not observed. When the numbers of fleahoppers found on plants were regressed on the numbers of fleahoppers observed in the terminal of those plants, the r2 and coefficient of variation (CV) values for adults were 0.81 and 40, respectively. Corresponding values for nymphs were 0.97 and 22. Based on regression slopes, the terminal accounted for 64% of the adults and 78% of the nymphs observed on plants. Our results suggest fleahopper counts obtained from terminal examinations accurately reflect the numbers of fleahoppers on those plants. However, this sampling practice may not provide the level of precision typically required in population research.