Northern fowl mites were monitored on a caged-layer operation in southern California for 22 mo. Three experienced observers underestimated actual numbers of mites in the vent region ≈80% of the time. Errors were higher for heavy infestations. Observer estimates were highly correlated with each other (r > 0.89, P < 0.01) and with mite numbers estimated by vent feather removal (r > 0.82, P < 0.01). Mites on hens varied between houses and over time. Molting consistently reduced mite numbers, but did not eliminate them in a flock. Long-term monitoring of individual sentinel hens demonstrated that some hens would support high numbers of mites for several months or more. Use of a new sequential hen sampling plan required ≈1 min per hen, if mite numbers were estimated. At this site, treatment decisions often could be reached in <20 min per house. Mite scores (index of estimated mites per hen) were well correlated with percentage of hens infested in both test houses. In a chronically infested house, prevalence of mites on eggs averaged 8.5%, with a range of 0–55%. Applications of tetrachlorvinphos-dichlorvos by the producer appeared to be based on mites on > about 20% of eggs. The chemical was marginal for controlling mites on hens (25% reduction in percentage of hens infested), but effectively reduced mites on eggs (95% fewer mites on eggs at 1 wk and 90% at 2 wk). When data were grouped by mite index score on hens, there was a strong relationship (r 2 = 0.83, P < 0.01) between mite prevalence on eggs and the scores of the hens which laid them. Sampling 100 eggs evenly spaced in a house required <7 min, and adult mites were easily seen. Sampling mites on eggs appears to be useful to localize at least high-level infestations, and egg-based sampling for mites merits further investigation.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 93 • No. 3