A Burkard recording volumetric spore trap and rainwater spore trap were operated in a highbush blueberry field in Michigan from 3 April to 11 June 1973.  Ascospores of Monilinia vaccinii-corymbosi, incitant of mummy berry disease, were trapped from air beginning 3 April, prior to bud break, until 8 May, when bushes were at 5% pink-bud-prebloom stage and leaves averaged 21 mm in length.  The peak ascospore count of 290 occurred on 19 April.

Conidia were first trapped from air on 7 May, 3 days prior to the appearance of leaf and shoot infections caused by ascospores.  The peak conidial count of 809 from air occurred on 9 May, and conidia were caught in diminishing numbers through 11 June, when bushes were at 100%-petal-fall stage.  Rain water collections of conidia in bushes occurred from 16 May to 11 June with peak counts of 857 conidia/ml occurring 30 May to 4 June, when bushes were at mid-petal-fall stage.

Early sprays of triforine but not benomyl applied on 17 and 25 April (new leaves 1-2 mm and 10 mm long, respectively) were effective in controlling primary infection by ascospores.  Late sprays of both triforine or benomyl applied on 11, 21, and 31 May (10% pink-bud prebloom, 14% bloom and 13% petal-fall stages, respectively) were effective in controlling secondary infection from conidia.  There were no yield differences between treatments and control due to a relatively low level of inoculum in the test field and variation in bush size.

Additional key words: Vaccinium, fungicide.