ISSN:
1572-9702
Keywords:
Phylloplane fungi
;
Alternari alternata
;
Tetranychus urticae
;
Panonychus ulmi
;
spider mites
;
population growth
;
competition
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract In a study on leaf-inhabiting tetranychid mites (Tetranychusurticae Koch–TSSM and Panonychus ulmi (Koch)–ERM)we investigated the effects of an extrinsic factor on the mites environment,namely phylloplane fungi. In a research orchard four trees were selected andtreated with an aerosol application of a phylloplane fungus (Alternariaalternata) in a tap-water emulsion. Applications were made immediatelyafter each sampling, with the exception of the last sample date. Twotap water controls for each treated tree were also sampled: a nearestneighbour (〈3 m from the treated trees) and a distant neighbour(〉30 m from the treated trees with other apple trees in between).Due to possible migration from the treated trees to near neighbours, thedistant control best reflected normal orchard conditions. Eight sampleswere taken throughout the 1994 growing season; however, appreciable mitepopulations were only observed on the last four sample dates. On the treatedtrees, the ERM maintained a steady low population (less than ten per leaf)whereas the TSSM showed a population outbreak (up to 44 mites per leaf).Conversely, on the distant trees, the TSSM maintained a low population(less than ten per leaf) while the ERM showed an outbreak (up to 33 perleaf). Observing on a leaf by leaf basis, when tetranychids were presenton a leaf, either one species dominated or the other, suggesting mutualcompetitive exclusion, the outcome of which was reversed to favour TSSMon trees that received an application of fungus. We concluded that theapplication of additional or supplemental amounts of A. alternatato apple leaves enhanced the population growth of TSSM compared to thatof ERM. Possible mechanisms are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1018483929822
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