Co-Authors:
Palevsky, E., Dept. of Entomology, ARO, Volcani Center, Bet Dagan 50250, Israel
Ucko, O., Crop Protection Dept., Extension Service, Min. of Agric. and Rural Development, Be'er Sheva 84100, Israel
Peles, S., Southern Arava R and D, M.P. Elot 88820, Israel
Yablonski, S., Dept. of Entomology, ARO, Volcani Center, Bet Dagan 50250, Israel
Gerson, U., Dept. of Entomology, Hebrew University of Jerusalem, Fac. Agric., Food/Environ. Qual. S., Rehovot 76100, Israel
Abstract:
In a study of date fruit damage caused by Oligonychus spp., we investigated whether the cultivar affects phenology, and on what hosts the mites over-winter. Samples were taken from 'Deglet Noor', 'Barhi' and 'Medjool' trees from mid-April through mid-September during the years 1999-2002. In the ground-cover mites were monitored by collecting Bermuda grass (Cynodon dactylon) under each sampling tree. Over 99% of the mites collected on Deglet Noor and Barhi fruit were identified as O. afrasiaticus. Mean population levels of O. afrasiaticus reached ten mites or more (initiation of infestation) on Medjool in the second half of May, whereas on Deglet Noor this did not occur before the first week of July. On Barhi the initiation of infestation varied between plots and years, ranging from the second half of May to the beginning of July, but always occurred earlier than Deglet Noor. Mite populations on the pinnae remained low from June through October, not exceeding seven mites per pinna, whereas on fruit strands they reached peak populations of approximately 4000 mites per strand. The sex ratio (proportion of females) of O. afrasiaticus on fruit of all three cultivars was highly female-biased, usually above 0.85. During winter, O. afrasiaticus was found on Bermuda grass in the orchard ground-cover as well as on fronds of all three cultivars.
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