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domingo, agosto 28, 2011

Varroa Growth weekly rate versus El Niño Southern Oscilation measured as MEI

Varroa Growth weekly rate versus El Niño Southern Oscilation measured as MEI

Based on data from Harris (2003)


and Internet for MEI.

ABSTRACT We measured signiÞcant variation in the instantaneous growth rates for varroa mites, Varroa destructor (Anderson & Trueman) from 1993 to 2002 in Baton Rouge, LA. Mite population growthwas monitored in colonies of honey bees, Apis mellifera L., withqueens from miscellaneous U.S. sources that had not been selectively bred for varroa resistance. Mite populations were measured at the beginning and end of short Þeld tests that started in the late spring of each year. Analyses of multiple regression showed that only the Þrst two of the following regressors were linear predictors of r, the instantaneous growth rate: 1) percentage of reproducing female mites, 2) proportion of total mites in capped brood, 3) mortality of mites in brood cells, 4) growthof the bee population, 5) capped brood area at the end of a test, and 6) duration of the test. Analysis of commonality indicated that the percentage of reproducing female mites explained 26% of the total variation in r, and the proportion of total mites in capped brood explained 6%. The joint expression of both variables accounted for another 4%. Thus, residual error reßected most of the total variation in r, which suggested posible climatic or environmental effects on mite growth. The lowest growth rates occurred in three consecutive years of drought in Louisiana. Measures of ambient temperature and relative humidity correlated to growthof mite populations among different years. Reduced growthrates were probably the result of diminished reproductive rates by varroa mites during periods of hot and dry weather.

Conclusion: not a perfect correlation but quite impresive.

Check your own records against this graph. what do you see? Is honey production, colony health, winter survival anyhow related to this MEI behaviour?

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