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ISHS Acta Horticulturae 1133: XI International Rubus and Ribes Symposium

Redberry mite population differences in two Rubus spp. on California's Central Coast

Authors:   M.E. Murrietta, M. Gaskell
Keywords:   'Ouachita', 'PrimeArk45', Acalitus essigi, tape extraction, phytoseiids, biological control
DOI:   10.17660/ActaHortic.2016.1133.66
Abstract:
Concern about redberry mites (RBM) (Acalitus essigi Hassan) has remained steady among blackberry (Rubus L subgenus Rubus Watson) growers on California's (USA) Central Coast. Current spray recommendations are based on the plant's physiological stage of development as these visual cues are clearer than following the lifecycle and movement of RBM. This study compared RBM populations in two common blackberry cultivars, 'PrimeArk 45' - a primocane fruiting cultivar - and 'Ouachita' - a floricane fruiting cultivar - to understand seasonal activity of RBM and to determine possible effects of cane management on population densities. Initial samples of fruit, flowers, and vegetative buds from both cultivars in September and October 2014 indicated that RBM numbers on 'Ouachita' were 90% greater than those on 'PrimeArk 45'. RBM was observed on 100% of the 'Ouachita' samples, but on less than 10% of 'PrimeArk 45' samples. A tape extraction method was initiated in November 2014 and found RBM emerged from 53% of 'Ouachita' fruit and 3% of vegetative buds and from 6% of 'PrimeArk 45' fruit and 16% of vegetative buds. These results suggest that the absence of an annual cut back or mow-down of floricanes provides RBM with continual resources allowing the population to overwinter and build up over time. Conversely, RBM's lifecycle is interrupted with the annual cut back of primocane fruiting cultivars.

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