Annual Report of The Kansai Plant Protection Society

Effects of partial soil sterilization for Tyrophagus similis Volgin were investigated. Soil sterilization treatments by solar heat, hot water, steam, and soil reduction were effective. Nevertheless, a few acarid mites survived in some cases in the greenhouses because of uneven heat treatment, or on the outskirts of greenhouses, and untreated areas. For that reason, we can not expect a lasting effect over a long period. It is not desirable that these soil sterilization methods be used in early summer. Short-term steam disinfection in spring or autumn will probably suppress acarid mite infestation. Use of this method will spread because of its economy and practicality if applied for prevention before mites' reproduction or as an emergency control measure after their outbreak.

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The effects of granular insecticides to the vegetable leafminer, Liriomyza sativae Blanchard, the serpentine leafminer, L. trifolii (Burgess), and the tomato leafminer, L. bryoniae (Kaltenbach), on kidney bean leaves were evaluated at 20°C under a 15L9D photoregime. Among 8 insecticides tested on second instar larvae, cartap and thiamethoxiam were highly toxic on the three Liriomyza species. None of the granular insecticides suppressed the number of oviposition and feeding punctures enough in any of the three Liriomyza species. Cartap, clothianidin, dinotefuran, nitenpyram, and thiamethoxiam were more toxic on the three Liriomyza species eggs.

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Wakayama Prefecture is one of the main production areas of persimmon in Japan. However, western flower thrips, Flankliniella occidentalis (Pergande) has been causing serious damage to persimmon fruit, especially variety Tonewase, when the fruit color turned yellow in early September since 1997. F. occidentalis overwintered on the perennial weed such as chickweed, Stellaria neglecta, and had two peaks of population density on undergrowth of persimmon orchards: one in June when perennial weeds were growing and the other in July-August when summer weeds were growing. Thus F. occidentalis maintained its population through various undergrowth. Since the weeding time was different between persimmon and mandarin orange orchards, the adult F. occidentalis dispersed from an orchard where they existed at a higher density to the adjacent orchards. Therefore, the population density of F. occidentalis was higher in a persimmon-mandarin orange cultivation area than in a persimmon mono-cultivation area. The thrips density on undergrowth of foxtail ears, Setalia viridis, was higher in the persimmon orchard than in the grassland nearby. This is provably because pesticides applied to persimmon trees suppressed the occurrence of natural enemies such as the minute bug, Orius sauteri, on weeds by drafting, causing a resurgence of F. occidentalis in persimmon orchards.

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Pesticide susceptibility of Liriomyza sativae Blanchard was evaluated. Ninety commercial insecticides and acaricides were tested by dipping kidney bean leaves infested with second instar larvae of L. sativae. Thirty-two chemicals including 13 organophosphates and 8 synthetic pyrethroids caused high mortalities of 90% or over. Eight chemicals commercially applicable to L. sativae in domestic fields were also examined for 4 local populations collected from different regions in Japan. Cyromazine, emamectin benzoate, milbemectin and spinosad were highly effective for the all populations. Flufenoxuron and tolfenpyrad showed different insecticidal activities among the populations.

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