Journal of Economic Entomology (2006) 99, 76-84

J.M. Renkema, J.P. Nyrop, C. Difonzo, M.K. Sears and A.W. Schaafsma (2006)
Control decision rule for European chafer (Coleoptera: Scarabaeidae) larvae in field corn
Journal of Economic Entomology 99 (1), 76-84
Abstract: After greenhouse and outdoor microplot experiments, a critical density of two third instars per microplot for third instars of European chafer, Rhizotrogus (Amphimallon) majalis (Razoumowsky), in corn, Zea mays L., was derived. On average, the number of missing or damaged plants increased ~ 8% from zero to two larvae per 900 cm². Furthermore, 23 fields in 2 yr were sampled for larvae along transects by using a golf cup cutter as the sampling tool and the critical density of 0.2 larva per sampling unit as the critical density. The sampling unit was one golf cup cutter with a diameter of 10.8 cm or 91.4 cm² (10 sampling units ~ 900 cm² ~ 1 foot²). Fieldwide means and variation were modeled to Taylor's power law, a = 1.42 and b = 1.47, and 20 of 23 fields fit the negative binomial probability distribution. Wald's formula for a sequential sampling plan was most accurate and least time-consuming, according to the operating characteristic and the average sample number function, relative to Iwao's and converging lines formulae. Percentage of sand, topography, soil bulk density, and proximity to trees were measured as potential predictors of areas with high larval density. Percentage of sand and soil bulk density were significant predictors, and topography and proximity to trees were not significant predictors. Field areas where the percentage of sand is high and the soil bulk density is low to moderate or where the percentage of sand is moderate and the soil bulk density is low should be chosen as sampling locations.
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Database assignments for author(s): Arthur W. Schaafsma, Justin M. Renkema, Jan P. Nyrop

Research topic(s) for pests/diseases/weeds:
control - general
surveys/sampling/distribution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Amphimallon majale	Maize/corn (Zea mays)