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Effects of Mulching and Pesticide Treatment on the Diversity, Abundance, and Succession of Arthropods on Chrysanthemum
Dissertation Abstract:
The effects of mulching and pesticide treatment on the diversity, abundance, and succession of arthropods associated with chrysanthemum were studied during the dry and wet seasons of 2002 in the experiment station of the University of Southern Mindanao at Kabacan, Cotabato.
A very rich fauna of 326 arthropod species were found to be associated with the leaves and flowers of chrysanthemum and on the topsoil and overlying hay mulch. The soil fauna was most diverse with 255 species, followed by fauna found in the flowers (50) and the leaves (21).
The spider mite, Tetranychus urticae Koch was the most abundant phytophagous species feeding on chrysanthemum leaves with higher population in pesticide-treated than untreated plots. Aphids, including the host specific Macrosiphoniella sanboni (Gillette), although present were much less abundant than the spider mite, indicating that they were still colonizing the area where the crop was new.
Predatory phytoseiid mites were present on the leaves although in rather low number. Flower inhabitants included mainly thrips and staphylinid beetles.
In the soil, detritivorous oribatids and the collembolans were abundant in almost all crop stages during both cropping seasons. Among the predators, insects especially staphylinids were the most abundant in both mulched and unmulched plots. Predatory mites were also relatively abundant, including gamasids belonging to the families Ascidae, Phytoseiidae, and Parasitidae, and prostigmatids like Cunaxidae.
Diversity and density of soil-inhabiting arthropods were higher in mulched plots than in unmulched ones obviously due to the abundance of food for detritivores that also encouraged the presence of more predatory species. Pesticide treatment did not affect the population of soil-inhabiting arthropods. Diversity indexes of soil arthropods were higher in the mulched than unmulched treatments, especially when untreated with pesticides.