Studies on water mite evolution regarding the phylogenetic implication are reviewed. Hydracarina is a large parasitengone mite group. Currently, more than 5, 000 species are integrated into 52 families in nine superfamilies. Although there are some conflicts on the origin of water mites, their monophyletic nature is suggested by several cladistic studies. The current taxonomic system of water mites does not reflect monophyletic groupings. Some researches have focused on phylogenetic relationships within Hydracarina, however, reliable hypotheses have not been obtained. Attempts to analyze data in a phylogenetic framework have been made in several ecological and behavioral studies. A comparative method has also been employed in a few studies, however, the real worth of this approach is not appreciated due to the absence of reliable phylogeny. Phylogenetic background estimated by modern cladistic methodology is indispensable for testing hypotheses on water mite evolution.

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Many young leaves of Pharping local pears were injured by a mite pest, Bryobia rubrioculus. Very young leaves sustained severe browning and sometimes withering in an orchard of the Horticulture Development Project, Phase II, in Kirtipur, Nepal. The percentage of damaged buds clearly increased with mite numbers both in Pharping local pear and European pear. On Pharping local pear, the percentage of buds heavily damaged buds reached a plateau of more than 90% when there was an average of ca. 20 mites per bud. Pharping local pear blossomed first, followed by European pear, Ussurian pear and Japanese pear in that order. Since the damage lessened with delay of the bloom, B. rubrioculus is not a serious pest to Japanese pear or Ussurian pear in Kirtipur.

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Mites associated with Apis cerana japonica were collected from worker bees and hive debris, reared in 3 regions in Japan between May, 1992 and January, 1993. Dominant species were Neocypholaelaps favas, Tyrophagus putrescentiae and Carpoglyphus lactis, which were assumed to be scavengers in the hives. Predacious and soil inhabiting mites were also collected but in small numbers. There were few mites attached to workers while hundreds of mites per gram were sometimes collected from hive debris. Two peaks in mite numbers appeared in July and October in a sampling site of Gunma Pref. but probably one peak in September in Aichi Pref. because the sampling was started in August. Few mites were collected from hives in Nagano. It was suspected that the mite numbers were influenced by temperature and precipitation. Most mites did not seem to reduce the bee populations or honey production.

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Spinach damage by the genus Tyrophagus was analyzed based on some scientific questionnaires requested to the agricultural authorities of 47 prefectures of Japan as well as our own observations from March to July 1999. Result showed that this genus spread all over the country’s commercial spinach growing areas. Damage was primarily observed at greenhouse in the early spring and late autumn. However, its level of damage was reported low to moderate probably due to short injury period. Because of differences in agronomic practices, the degree of spinach damage was varied among the growers rather than eight regions inquired. The survey revealed that the damage was often recognized within the last 5 years. According to the replies, it showed 50.0%, 27.1%, 18.8% and 4.2% of fluctuating, stable, increasing and decreasing infestation trends, respectively. Manure application, especially immature manure produced from rice straw or chaff seems to encourage these mites population density. Information collected on the application of synthetic pesticides to control these mites showed that DDVP (50% EC) did not provide their control consistently, probably due to mites dwelling behavior (restricted to spinach buds and soil). Besides, DCIP (30% G) may provide satisfactory control but unfortunately a few commercial growers use it. Others do not like to apply it because of unpleasant smell during application. Based on the 20 spinach and 8 soil samples received from the 13 prefectures, we identified T. similis in all samples except the samples examined from Yamaguchi (Mine) and Kagoshima, which indicated that this was the dominant species to be needed pest management interventions.

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