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1 April 2000 Presence-Absence Sequential Sampling Plan for Northern Fowl Mite, Ornithonyssus sylviarum (Acari: Macronyssidae), on Caged-layer Hens
Mary A. Harris, Michael J. Brewer, Jeffery A. Meyer
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Caged-layer hens were scored as infested or uninfested by visual examination of the vent region, and the number of northern fowl mite, Ornithonyssus sylviarum (Canestrini & Fanzago), per hen was estimated. The proportion infested and average number of mites per hen were shown to have a highly significant, positive relationship (r = 0.936). Sampling among houses within a flock, and rows and sections within houses were analyzed to determine the reliability of sampling a representative portion of a flock. Low- and moderate-tolerance treatment thresholds, based on percentage of hens infested with mites, were developed from sampling 1 wk before and 1 wk after acaricide treatments determined necessary by the producer. These thresholds were used to compare a fixed (single) sampling plan, a curtailed procedure of the fixed sampling plan, and a sequential sampling plan based on a sequential probability ratio test, by sampling 174 hens (the maximum number needed for the single sampling plan). The sequential sampling plan required fewer hen examinations on average to reach a treatment decision than did the other plans, depending on the infestation tolerance limits. Using a low tolerance approach in which infestations below 15% are considered noneconomic (safe threshold) and infestations above 25% are considered economically important (action threshold), as few as 5 hens required examination to reach a treatment decision. Sequential sampling plan graphs are presented for 2 tolerance threshold scenarios (a 15% safe-threshold paired with a 25% action threshold and a 35% safe-threshold paired with a 45% action threshold). These sequential sampling plans using presence absence assessments should greatly facilitate monitoring and treatment decisions for this important pest.

Mary A. Harris, Michael J. Brewer, and Jeffery A. Meyer "Presence-Absence Sequential Sampling Plan for Northern Fowl Mite, Ornithonyssus sylviarum (Acari: Macronyssidae), on Caged-layer Hens," Journal of Economic Entomology 93(2), 544-549, (1 April 2000).
Received: 15 March 1999; Accepted: 1 August 1999; Published: 1 April 2000

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